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Meningitis

Meningitis

Definition

Meningitis is a potentially fatal inflammation of the meninges, the thin, membranous covering of the brain and the spinal cord. Meningitis is most commonly caused by infection by bacteria, viruses, or fungi, although it can also be caused by bleeding into the meninges, cancer , diseases of the immune system, and an inflammatory response to certain types of chemotherapy or other chemical agents. The most serious and the most difficult to treat types of meningitis tend to be those caused by bacteria.

Description

Meningitis is a particularly dangerous infection because of the very delicate nature of the brain. Brain cells are some of the only cells in the body that, once killed, will not regenerate themselves. Therefore, if enough brain tissue is damaged by an infection, then serious lifelong handicaps will remain.

In order to learn about meningitis, it is important to have a basic understanding of the anatomy of the brain. The meninges are three separate membranes, layered together, which encase the brain and spinal cord:

  • The dura is the toughest, outermost layer, and is closely attached to the inside of the skull.
  • The middle layer, the arachnoid, is important because of its involvement in the normal flow of the cerebrospinal fluid (CSF), a lubricating and nutritive fluid that bathes both the brain and the spinal cord.
  • The innermost layer, the pia, helps direct blood vessels into the brain.
  • The space between the arachnoid and the pia contains CSF, which helps insulate the brain from trauma. Many blood vessels, as well as peripheral and cranial nerves course through this space.

CSF, produced within specialized chambers deep inside the brain, flows over the surface of the brain and spinal cord. This fluid serves to cushion these relatively delicate structures, as well as supplying important nutrients for brain cells. CSF is reabsorbed by blood vessels located within the meninges. A careful balance between CSF production and reabsorption is important to avoid the accumulation of too much CSF.

Because the brain is enclosed in the hard, bony case of the skull, any disease that produces swelling will be damaging to the brain. The skull cannot expand at all, so when the swollen brain tissue pushes up against the skull's hard bone, the brain tissue becomes damaged and the blood supply is compromised, and this tissue may ultimately die. Furthermore, swelling on the right side of the brain will not only cause pressure and damage to that side of the brain, but by taking up precious space within the tight confines of the skull, the left side of the brain will also be pushed up against the hard surface of the skull, causing damage to the left side of the brain, as well.

Another way that infections injure the brain involves the way in which the chemical environment of the brain changes in response to the presence of an infection. The cells of the brain require a very well-regulated environment. Careful balance of oxygen, carbon dioxide, sugar (glucose), sodium, calcium, potassium , and other substances must be maintained in order to avoid damage to brain tissue. An infection upsets this balance, and brain damage can occur when the cells of the brain are either deprived of important nutrients or exposed to toxic levels of particular substances.

The cells lining the brain's tiny blood vessels (capillaries) are specifically designed to prevent many substances from passing into brain tissue. This is commonly referred to as the blood-brain barrier. The blood-brain barrier prevents various substances that could be poisonous to brain tissue (toxins), as well as many agents of infection, from crossing from the blood stream into the brain tissue. While this barrier is obviously an important protective feature for the brain, it also serves to complicate treatment in the case of an infection by making it difficult for medications to pass out of the blood and into the brain tissue where the infection is located.

Causes & symptoms

The most common infectious causes of meningitis vary according to an individual's age, habits, living environment, and health status. While nonbacterial types of meningitis are more common, bacterial meningitis is more potentially life-threatening. Three bacterial agents are responsible for about 80% of all bacterial meningitis cases. These bacteria are Haemophilus influenzae type b, Neisseria meningitidis (causing meningococcal meningitis), and Streptococcus pneumoniae (causing pneumococcal meningitis).

In newborns, the most common agents of meningitis are those that are contracted from the newborn's mother, including Group B streptococci (becoming an increasingly common infecting organism in the newborn period), Escherichia coli, and Listeria monocytogenes. The highest incidence of meningitis occurs in babies under a month old, with an increased risk of meningitis continuing through about two years of age.

Older children are more frequently infected by bacteria, including Haemophilus influenzae, Neisseria meningitidis, and Streptococcus pneumoniae.

Adults are most commonly infected by either S. pneumoniae or N. meningitidis, with pneumococcal meningitis the more common. Certain conditions predispose to this type of meningitis, including alcoholism and chronic upper respiratory tract infections (especially of the middle ear, sinuses, and mastoids).

N. meningitidis is the only organism that can cause epidemics of meningitis. For instance, cases have been reported when a child in a crowded day care situation or a military recruit in a crowded training camp has fallen ill with meningococcal meningitis.

There have been case reports in recent years of meningitis caused by Streptococcus bovis, an organism that is ordinarily found in the digestive tract of such animals as cows and sheep; and Pasteurella multocida, an organism that usually infects rabbits. Other atypical cases of meningitis include several caused by the anthrax bacillus. These cases have a high mortality rate.

Viral causes of meningitis include the herpes simplex virus, the mumps and measles viruses (against which most children are protected due to mass immunization programs), the virus that causes chickenpox , the rabies virus, and a number of viruses that are acquired through the bites of infected mosquitoes.

A number of medical conditions predispose individuals to meningitis caused by specific organisms. Patients with AIDS (acquired immunodeficiency syndrome) are more prone to getting meningitis from fungi, as well as from the agent that causes tuberculosis . Patients who have had their spleens removed, or whose spleens are no longer functional (as in the case of patients with sickle cell disease) are more susceptible to other infections, including meningococcal and pneumococcal meningitis.

The majority of meningitis infections are acquired by transmission through the blood. A person may have another type of infection (for instance, infection of the lungs, throat, or tissues of the heart) caused by an organism that can also cause meningitis. If this initial infection is not properly treated, the organism will continue to multiply, find its way into the blood stream, and be delivered in sufficient quantities to invade past the blood-brain barrier. Direct spread occurs when an organism spreads to the meninges from infected tissue next to or very near the meninges. This can occur, for example, with a severe, poorly treated ear or sinus infection .

Patients who suffer from skull fractures possess abnormal openings to the sinuses, nasal passages, and middle ears. Organisms that usually live in the human respiratory system without causing disease can pass through openings caused by such fractures, reach the meninges, and cause infection. Similarly, patients who undergo surgical procedures or who have had foreign bodies surgically placed within their skulls (such as tubes to drain abnormal amounts of accumulated CSF) have an increased risk of meningitis.

Organisms can also reach the meninges via an uncommon but interesting method called intraneural spread. This involves an organism invading the body at a considerable distance away from the head, spreading along a nerve, and using that nerve as a sort of ladder into the skull, where the organism can multiply and cause meningitis. Herpes simplex virus is known to use this type of spread, as is the rabies virus.

The classic symptoms of meningitis (particularly of bacterial meningitis) include fever, headache, vomiting , sensitivity to light (photophobia), irritability, severe fatigue (lethargy), stiff neck, and a reddish purple rash on the skin. Untreated, the disease progresses with seizures, confusion, and eventually coma.

A very young infant may not show the classic signs of meningitis. Early in infancy, a baby's immune system is not yet developed enough to mount a fever in response to infection, so fever may be absent. However, checking an infant's temperature to see if it is high or low could be an indication. Some infants with meningitis have seizures as their only identifiable symptom. Similarly, debilitated elderly patients may not have fever or other identifiable symptoms of meningitis.

Damage due to meningitis occurs from a variety of phenomena. The action of infectious agents on the brain tissue is one direct cause of damage. Other types of damage may be due to the mechanical effects of swelling and compression of brain tissue against the bony surface of the skull. Swelling of the meninges may interfere with the normal absorption of CSF by blood vessels, causing accumulation of CSF and damage from the resulting pressure on the brain. Interference with the brain's carefully regulated chemical environment may cause damaging amounts of normally present substances (carbon dioxide, potassium) to accumulate. Inflammation may cause the blood-brain barrier to become less effective at preventing the passage of toxic substances into brain tissue.

Diagnosis

A number of techniques are used when examining a patient suspected of having meningitis to verify the diagnosis. Certain manipulations of the head (lowering the head, chin towards chest, for example) are difficult to perform and painful for a patient with meningitis.

The most important test used to diagnose meningitis is the lumbar puncture (LP), commonly called a spinal tap. Lumbar puncture involves the insertion of a thin needle into a space between the vertebrae in the lower back and the withdrawal of a small amount of CSF. The CSF is then examined under a microscope to look for bacteria or fungi. Normal CSF contains set percentages of glucose and protein. These percentages will vary with bacterial, viral, or other causes of meningitis. For example, bacterial meningitis causes a smaller than normal percentage of glucose to be present in CSF, as the bacteria are essentially "eating" the host's glucose, and using it for their own nutrition and energy production. Normal CSF should contain no infection-fighting cells (white blood cells), so the presence of white blood cells in CSF is another indication of meningitis. Some of the withdrawn CSF is also put into special lab dishes to allow growth of the suspected infecting organism, which can then be identified more easily. Special immunologic and serologic tests may also be used to help identify the infectious agent.

In rare instances, CSF from a lumbar puncture cannot be examined because the amount of swelling within the skull is so great that the pressure within the skull (intracranial pressure) is extremely high. This pressure is always measured immediately upon insertion of the LP needle. If it is found to be very high, no fluid is withdrawn because doing so could cause herniation of the brain stem. Herniation of the brain stem occurs when the part of the brain connecting to the spinal cord is thrust through the opening at the base of the skull into the spinal canal. Such herniation will cause compression of those structures within the brain stem that control the most vital functions of the body (breathing, heart beat, consciousness). Death or permanent debilitation follows herniation of the brain stem.

Treatment

Because meningitis is a potentially deadly condition, doctors should be contacted immediately for diagnosis and treatment. Alternative treatments should be used only to support the recovery process following appropriate antibiotic treatments, or used concurrently with antibiotic treatments.

General recommendations

Patients should be well rested in bed, preferably in a darkened room. They should be given lots of fluids and nutritious foods. Patients should avoid processed foods and those with high fat and sugar content. Fats are difficult to digest in severely ill patients; sugar tends to depress the immune system and impede recovery process. Patients should also take vitamin A (up to 10,000 IU per day), B-complex vitamins (up to 1,500 mg per day), and vitamin C (up to 2 g per day) to help keep the body strong and prevent future infections. Additionally, the patient may consider taking other antioxidants, essential fatty acids (EFAs), and/or participate in therapies, such as massage therapy and movement therapies (e.g., t'ai chi ).

Other treatments

Alternative therapies, such as homeopathy, traditional Chinese medicine , and Western herbal medicine may help patients regain their health and build up their immune systems. The recovering individual, under the direction of a professional alternative therapist, may opt to include mushrooms into his or her diet to stimulate immune function. Contact an experienced herbalist or homeopathic practitioner for specific remedies.

Allopathic treatment

Antibiotics are the first line of treatment for bacterial meningitis. In recent years, however, doctors have turned to such newer medications as vancomycin or the fluoroquinolones to treat bacterial meningitis because strains of S. pneumoniae and N. meningitidis have emerged that are resistant to penicillin and the older antibiotics. Because of the effectiveness of the blood-brain barrier in preventing the passage of substances into the brain, medications must be delivered directly into the patient's veins (intravenously) at very high doses. Antiviral drugs (acyclovir) may be helpful in shortening the course of viral meningitis, and antifungal medications are available as well. Patients who develop seizures will require medications to halt the seizures and prevent their return.

Expected results

Viral meningitis is the least severe type of meningitis, and patients usually recover with no long-term effects from the infection. Bacterial infections, however, are much more severe, and progress rapidly. Without very rapid treatment with the appropriate antibiotic, the infection can swiftly lead to coma and death in less than a day's time. While death rates from meningitis vary depending on the specific infecting organism, the overall death rate is just under 20%.

The most frequent long-term effects of meningitis include deafness and blindness, which may be caused by the compression of specific nerves and brain areas responsible for the senses of hearing and sight. Some patients develop permanent seizure disorders, requiring lifelong treatment with antiseizure medications. Scarring of the meninges may result in obstruction of the normal flow of CSF, causing abnormal accumulation of CSF. This may be a chronic problem for some patients, requiring the installation of shunt tubes to drain the accumulation regularly.

Some cases of sudden and unexplained death in adults have been attributed to rapidly developing meningitis.

Prevention

Prevention of meningitis primarily involves the appropriate treatment of other infections an individual may acquire, particularly those that have a track record of seeding to the meninges (such as ear and sinus infections). Preventive treatment with antibiotics is sometimes recommended for the close contacts of an individual who is ill with meningococcal or H. influenzae type b meningitis. A meningococcal vaccine exists, and is sometimes recommended to individuals who are traveling to very high risk areas. A vaccine for H. influenzae type b is now given to babies as part of the standard array of childhood immunizations.

Resources

BOOKS

"Meningitis." The Medical Advisor: The Complete guide to Alternative & Conventional Treatments. Home Edition. Richmond, VA: Time Life Inc., 1997.

Ray, C. George. "Central Nervous System Infections." In Sherris Medical Microbiology: An Introduction to Infectious Diseases, edited by Kenneth J. Ryan. Norwalk, CT: Appleton and Lange, 1994.

Swartz, Morton N. "Bacterial Meningitis." In Cecil Textbook of Medicine, edited by J. Claude Bennett and Fred Plum. Philadelphia: W.B. Saunders, 1996.

PERIODICALS

Aronin, S. I. "Current Pharmacotherapy of Pneumococcal Meningitis." Expert Opinion on Pharmacotherapy 3 (February 2002): 121129.

Black, M., and D. I Graham. "Sudden Unexplained Death in Adults Caused by Intracranial Pathology." Journal of Clinical Pathology 55 (January 2002): 4450.

Green, B. T., K. M. Ramsey, and P. E. Nolan. "Pasteurella multocida Meningitis: Case Report and Review of the Last 11 Years." Scandinavian Journal of Infectious Disease 34 (2002): 213217.

Meissner, Judith W. "Caring for Patients With Meningitis." Nursing (July 1995): 50+.

Schuchat, Anne, et al. "Bacterial Meningitis in the United States in 1995." New England Journal of Medicine (October 2, 1997).

Tasyaran, M. A., O. Deniz, M. Ertek, and K. Cetin. "Anthrax Meningitis: Case Report and Review." Scandinavian Journal of Infectious Diseases 34 (2002): 6667.

Tunkel, A. R., and W. M. Scheld. "Treatment of Bacterial Meningitis." Current Infectious Disease Reports 4 (February 2002): 716.

Vilarrasa, N., A. Prats, M. Pujol, et al. "Streptococcus bovis Meningitis in a Healthy Adult Patient." Scandinavian Journal of Infectious Diseases 34 (2002): 6162.

ORGANIZATIONS

American Academy of Neurology. 1080 Montreal Avenue, St. Paul, MN 55116. (612) 695-1940. <http://www.aan.com>.

Meningitis Foundation of America. 7155 Shadeland Station, Suite 190, Indianapolis, IN 46256-3922. (800) 668-1129. <http://www.musa.org/welcome.htm>.

Mai Tran

Rebecca J. Frey, PhD

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Meningitis

Meningitis

Definition

Meningitis is a serious inflammation of the meninges, the thin, membranous covering of the brain and the spinal cord. Meningitis is most commonly caused by infection (by bacteria, viruses, or fungi), although it can also be caused by bleeding into the meninges, cancer, diseases of the immune system, and an inflammatory response to certain types of chemotherapy or other chemical agents. The most serious and difficult-to-treat types of meningitis tend to be those caused by bacteria. In some cases, meningitis can be a potentially fatal condition.

Description

Meningitis is a particularly dangerous infection because of the very delicate nature of the brain. Brain cells are some of the only cells in the body that, once killed, will not regenerate themselves. Therefore, if enough brain tissue is damaged by an infection, serious, life-long handicaps will remain.

In order to learn about meningitis, it is important to have a basic understanding of the anatomy of the brain. The meninges are three separate membranes, layered together, which encase the brain and spinal cord:

  • The dura is the toughest, outermost layer, and is closely attached to the inside of the skull.
  • The middle layer, the arachnoid, is important because of its involvement in the normal flow of the cerebrospinal fluid (CSF), a lubricating and nutritive fluid that bathes both the brain and the spinal cord.
  • The innermost layer, the pia, helps direct blood vessels into the brain.
  • The space between the arachnoid and the pia contains CSF, which helps insulate the brain from trauma. Many blood vessels course through this space.

CSF, produced within specialized chambers deep inside the brain, flows over the surface of the brain and spinal cord. This fluid serves to cushion these relatively delicate structures, as well as supplying important nutrients for brain cells. CSF is reabsorbed by blood vessels located within the meninges. A careful balance between CSF production and reabsorption is important to avoid the accumulation of too much CSF.

Because the brain is enclosed in the hard, bony case of the skull, any disease that produces swelling will be damaging to the brain. The skull cannot expand at all, so when the swollen brain tissue pushes up against the skull's hard bone, the brain tissue becomes damaged and may ultimately die. Furthermore, swelling on the right side of the brain will not only cause pressure and damage to that side of the brain, but by taking up precious space within the tight confines of the skull, the left side of the brain will also be pushed up against the hard surface of the skull, causing damage to the left side of the brain as well.

Another way that infections injure the brain involves the way in which the chemical environment of the brain changes in response to the presence of an infection. The cells of the brain require a very well-regulated environment. Careful balance of oxygen, carbon dioxide, sugar (glucose), sodium, calcium, potassium, and other substances must be maintained in order to avoid damage to brain tissue. An infection upsets this balance, and brain damage can occur when the cells of the brain are either deprived of important nutrients or exposed to toxic levels of particular substances.

HATTIE ALEXANDER (19011968)

Hattie Alexander, a dedicated pediatrician, medical educator, and researcher in microbiology, won international recognition for deriving a serum to combat influenzal meningitis, a common disease that previously had been nearly always fatal to infants and young children. Alexander subsequently investigated microbiological genetics and the processes whereby bacteria, through genetic mutation, acquire resistance to antibiotics. In 1964, as president of the American Pediatric Society, she became one of the first women to head a national medical association.

As an intern at the Harriet Lane Home of Johns Hopkins Hospital from 1930 to 1931, Alexander became interested in influenzal meningitis. The source of the disease was Hemophilus influenzae, a bacteria that causes inflammation of the meninges, the membranes surrounding the brain and spinal cord. In 1931, Alexander began a second internship at the Babies Hospital of the Columbia-Presbyterian Medical Center in New York City. There, she witnessed first-hand the futility of medical efforts to save babies who had contracted influenzal meningitis.

Alexander's early research focused on deriving a serum (the liquid component of blood, in which antibodies are contained) that would be effective against influenzal meningitis. Serums derived from animals that have been exposed to a specific disease-producing bacterium often contain antibodies against the disease and can be developed for use in immunizing humans against it. Alexander knew that the Rockefeller Institute in New York City, however, had been able to prepare a rabbit serum for the treatment of pneumonia, another bacterial disease. Alexander therefore experimented with rabbit serums, and by 1939 was able to announce the development of a rabbit serum effective in curing infants of influenzal meningitis.

In the early 1940s, Alexander experimented with the use of drugs in combination with rabbit serum in the treatment of influenzal meningitis. Within the next two years, she saw infant deaths due to the disease drop by eighty percent.

The cells lining the brain's tiny blood vessels (capillaries) are specifically designed to prevent many substances from passing into brain tissue. This is commonly referred to as the blood-brain barrier. The blood-brain barrier prevents various substances that could be poisonous to brain tissue (toxins), as well as many agents of infection, from crossing from the blood stream into the brain tissue. While this barrier is obviously an important protective feature for the brain, it also serves to complicate treatment in the case of an infection by making it difficult for medications to pass out of the blood and into the brain tissue where the infection is located.

Causes and symptoms

The most common infectious causes of meningitis vary according to an individual's age, habits, living environment, and health status. While nonbacterial types of meningitis are more common, bacterial meningitis is the more potentially life-threatening. Three bacterial agents are responsible for about 80% of all bacterial meningitis cases. These bacteria are Haemophilus influenzae type b, Neisseria meningitidis (causing meningococcal meningitis), and Streptococcus pneumoniae (causing pneumococcal meningitis).

In newborns, the most common agents of meningitis are those that are contracted from the newborn's mother, including Group B streptococci (becoming an increasingly common infecting organism in the newborn period), Escherichia coli, and Listeria monocytogenes. The highest incidence of meningitis occurs in babies under a month old, with an increased risk of meningitis continuing through about two years of age.

Older children are more frequently infected by the bacteria Haemophilus influenzae, Neisseria meningitidis, and Streptococci pneumoniae.

Adults are most commonly infected by either S. pneumoniae or N. meningitidis, with pneumococcal meningitis the more common. Certain conditions predispose to this type of meningitis, including alcoholism and chronic upper respiratory tract infections (especially of the middle ear, sinuses, and mastoids).

N. meningitidis is the only organism that can cause epidemics of meningitis. In particular, these have occurred when a child in a crowded day-care situation or a military recruit in a crowded training camp has fallen ill with meningococcal meningitis.

Viral causes of meningitis include the herpes simplex virus, the mumps and measles viruses (against which most children are protected due to mass immunization programs), the virus that causes chicken pox, the rabies virus, and a number of viruses that are acquired through the bites of infected mosquitoes.

A number of medical conditions predispose individuals to meningitis caused by specific organisms. Patients with AIDS (acquired immune deficiency syndrome) are more prone to getting meningitis from fungi, as well as from the agent that causes tuberculosis. Patients who have had their spleens removed, or whose spleens are no longer functional (as in the case of patients with sickle cell disease ) are more susceptible to other infections, including meningococcal and pneumococcal meningitis.

The majority of meningitis infections are acquired by blood-borne spread. A person may have another type of infection (of the lungs, throat, or tissues of the heart) caused by an organism that can also cause meningitis. If this initial infection is not properly treated, the organism will continue to multiply, find its way into the blood stream, and be delivered in sufficient quantities to invade past the blood brain barrier. Direct spread occurs when an organism spreads to the meninges from infected tissue next to or very near the meninges. This can occur, for example, with a severe, poorly treated ear or sinus infection.

Patients who suffer from skull fractures possess abnormal openings to the sinuses, nasal passages, and middle ears. Organisms that usually live in the human respiratory system without causing disease can pass through openings caused by such fractures, reach the meninges, and cause infection. Similarly, patients who undergo surgical procedures or who have had foreign bodies surgically placed within their skulls (such as tubes to drain abnormal amounts of accumulated CSF) have an increased risk of meningitis.

Organisms can also reach the meninges via an uncommon but interesting method called intraneural spread. This involves an organism invading the body at a considerable distance away from the head, spreading along a nerve, and using that nerve as a kind of ladder into the skull, where the organism can multiply and cause meningitis. Herpes simplex virus is known to use this type of spread, as is the rabies virus.

The most classic symptoms of meningitis (particularly of bacterial meningitis) include fever, headache, vomiting, sensitivity to light (photophobia), irritability, severe fatigue (lethargy), stiff neck, and a reddish purple rash on the skin. Untreated, the disease progresses with seizures, confusion, and eventually coma.

A very young infant may not show the classic signs of meningitis. Early in infancy, a baby's immune system is not yet developed enough to mount a fever in response to infection, so fever may be absent. Some infants with meningitis have seizures as their only identifiable symptom. Similarly, debilitated elderly patients may not have fever or other identifiable symptoms of meningitis.

Damage due to meningitis occurs from a variety of phenomena. The action of infectious agents on the brain tissue is one direct cause of damage. Other types of damage may be due to the mechanical effects of swelling and compression of brain tissue against the bony surface of the skull. Swelling of the meninges may interfere with the normal absorption of CSF by blood vessels, causing accumulation of CSF and damage from the resulting pressure on the brain. Interference with the brain's carefully regulated chemical environment may cause damaging amounts of normally present substances (carbon dioxide, potassium) to accumulate. Inflammation may cause the blood-brain barrier to become less effective at preventing the passage of toxic substances into brain tissue.

Diagnosis

A number of techniques are used when examining a patient suspected of having meningitis to verify the diagnosis. Certain manipulations of the head (lowering the head, chin towards chest, for example) are difficult to perform and painful for a patient with meningitis.

The most important test used to diagnose meningitis is the lumbar puncture (commonly called a spinal tap). Lumbar puncture (LP) involves the insertion of a thin needle into a space between the vertebrae in the lower back and the withdrawal of a small amount of CSF. The CSF is then examined under a microscope to look for bacteria or fungi. Normal CSF contains set percentages of glucose and protein. These percentages will vary with bacterial, viral, or other causes of meningitis. For example, bacterial meningitis causes a greatly lower than normal percentage of glucose to be present in CSF, as the bacteria are essentially "eating" the host's glucose, and using it for their own nutrition and energy production. Normal CSF should contain no infection-fighting cells (white blood cells), so the presence of white blood cells in CSF is another indication of meningitis. Some of the withdrawn CSF is also put into special lab dishes to allow growth of the infecting organism, which can then be identified more easily. Special immunologic and serologic tests may also be used to help identify the infectious agent.

In rare instances, CSF from a lumbar puncture cannot be examined because the amount of swelling within the skull is so great that the pressure within the skull (intracranial pressure) is extremely high. This pressure is always measured immediately upon insertion of the LP needle. If it is found to be very high, no fluid is withdrawn because doing so could cause herniation of the brain stem. Herniation of the brain stem occurs when the part of the brain connecting to the spinal cord is thrust through the opening at the base of the skull into the spinal canal. Such herniation will cause compression of those structures within the brain stem that control the most vital functions of the body (breathing, heart beat, consciousness). Death or permanent debilitation follows herniation of the brain stem.

Treatment

Antibiotic medications (forms of penicillin and cephalosporins, for example) are the most important element of treatment against bacterial agents of meningitis. Because of the effectiveness of the blood-brain barrier in preventing the passage of substances into the brain, medications must be delivered directly into the patient's veins (intravenously, or by IV), at very high doses. Antiviral drugs (acyclovir) may be helpful in shortening the course of viral meningitis, and antifungal medications are available as well.

Other treatments for meningitis involve decreasing inflammation (with steroid preparations) and paying careful attention to the balance of fluids, glucose, sodium, potassium, oxygen, and carbon dioxide in the patient's system. Patients who develop seizures will require medications to halt the seizures and prevent their return.

KEY TERMS

Blood-brain barrier An arrangement of cells within the blood vessels of the brain that prevents the passage of toxic substances, including infectious agents, from the blood and into the brain. It also makes it difficult for certain medications to pass into brain tissue.

Cerebrospinal fluid (CSF) Fluid made in chambers within the brain which then flows over the surface of the brain and spinal cord. CSF provides nutrition to cells of the nervous system, as well as providing a cushion for the nervous system structures. It may accumulate abnormally in some disease processes, causing pressure on and damage to brain structures.

Lumbar puncture (LP) A medical test in which a very narrow needle is inserted into a specific space between the vertebrae of the lower back in order to draw off a sample of CSF for further examination.

Meninges The three-layer membranous covering of the brain and spinal cord, composed of the dura, arachnoid, and pia. It provides protection for the brain and spinal cord, as well as housing many blood vessels and participating in the appropriate flow of CSF.

Prognosis

Viral meningitis is the least severe type of meningitis, and patients usually recover with no long-term effects from the infection. Bacterial infections, however, are much more severe, and progress rapidly. Without very rapid treatment with the appropriate antibiotic, the infection can swiftly lead to coma and death in less than a day's time. While death rates from meningitis vary depending on the specific infecting organism, the overall death rate is just under 20%.

The most frequent long-term effects of meningitis include deafness and blindness, which may be caused by the compression of specific nerves and brain areas responsible for the senses of hearing and sight. Some patients develop permanent seizure disorders, requiring life-long treatment with anti-seizure medications. Scarring of the meninges may result in obstruction of the normal flow of CSF, causing abnormal accumulation of CSF. This may be a chronic problem for some patients, requiring the installation of shunt tubes to drain the accumulation regularly.

Prevention

Prevention of meningitis primarily involves the appropriate treatment of other infections an individual may acquire, particularly those that have a track record of seeding to the meninges (such as ear and sinus infections). Preventive treatment with antibiotics is sometimes recommended for the close contacts of an individual who is ill with meningococcal or H. influenzae type b meningitis. A meningococcal vaccine exists, and is sometimes recommended to individuals who are traveling to very high risk areas. A vaccine for H. influenzae type b is now given to babies as part of the standard array of childhood immunizations.

Resources

ORGANIZATIONS

American Academy of Neurology. 1080 Montreal Ave., St. Paul, MN 55116. (612) 695-1940. http://www.aan.com.

Meningitis Foundation of America. 7155 Shadeland Station, Suite 190, Indianapolis, IN 46256-3922. (800) 668-1129. http://www.musa.org/welcome.htm.

Cite this article
Pick a style below, and copy the text for your bibliography.

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Meningitis

Meningitis

Definition

Meningitis is a serious inflammation of the meninges, the membranes (lining) that surround the brain and spinal cord. It can be of bacterial, viral, or fungal origin.

Description

Meningitis is usually the result of a viral or bacterial infection. Viral meningitis, also called aseptic meningitis, is generally less severe and often disappears without specific treatment, while bacterial meningitis can be quite serious and may result in brain damage, hearing loss, or learning disabilities in children. The infection may even cause death.

Bacterial meningitis is either monococcal or pneumococcal, depending on the type of bacteria responsible for the infection. Meningitis caused by Haemophilus influenzae and related strains (A, B C, Y, and W135) is also called meningococcal meningitis. Similarly, meningitis due to Streptococcus pneumoniae is also called pneumococcal meningitis.

Transmission

Most types of meningitis are contagious. A person may be exposed to meningitis bacteria when someone with meningitis coughs or sneezes. The bacteria can also spread through kissing or sharing eating utensils or a toothbrush.

Demographics

According to the National Institute of Neurological Disorders and Stroke (NINDS), some 6,000 cases of pneumococcal meningitis are reported in the United States each year. Meningococcal meningitis is common in minors ages two to 18. Each year about 2,600 people get this highly contagious disease. High-risk groups include infants under the age of one year, people with suppressed immune systems, travelers to foreign countries where the disease is endemic, and college students and Army recruits who reside in dormitories and other close quarters. Between 10 and 15 percent of cases are fatal, with another 10 to 15 percent involving brain damage and other serious side effects.

Causes and symptoms

The bacteria which cause bacterial meningitis live in the back of the nose and throat region and are carried by 10 to 25 percent of the population. They cause meningitis when they get into the bloodstream and travel to the meninges.

At least 50 kinds of bacteria can cause bacterial meningitis. According to the Centers for Disease Control (CDC), before the 1990s, Haemophilus influenzae type b (Hib) was the leading cause of bacterial meningitis, but subsequent vaccines given to all children as part of their routine immunizations have reduced the occurrence of the disease due to H. influenzae. As of 2004, Streptococcus pneumoniae and Neisseria meningitidis were the leading causes of bacterial meningitis.

In newborns, the most common agents of meningitis are those that are contracted from the newborn's mother, including Group B streptococci (becoming an increasingly common infecting organism in the newborn period), Escherichia coli, and Listeria monocytogenes. The highest incidence of meningitis occurs in babies less than a month old, with an increased risk of meningitis continuing through about two years of age.

Older children are more frequently infected by the bacteria Haemophilus influenzae, Neisseria meningitidis, and Streptococci pneumoniae.

Most cases of viral meningitis are caused by enteroviruses (viruses that typically cause stomach flu). However, many other types of viruses, such as the herpes simplex virus, the mumps and measles viruses (against which most children are protected due to mass immunization programs), the virus that causes chickenpox , the rabies virus, and a number of viruses that are acquired through the bites of infected mosquitoes.

Meningitis symptoms include high fever , headache , and stiff neck in children over the age of two years. These symptoms can develop over several hours, or they may take one to two days. Other symptoms may include nausea , vomiting , discomfort looking into bright lights, confusion, and sleepiness. In some cases, a rash may be present. In newborns and small infants, these symptoms may be absent or difficult to detect, and the infant may only appear slow or inactive, or be irritable, have vomiting, or be feeding poorly. As the disease progresses, patients of any age may also have seizures.

When to call the doctor

Parents should call a doctor if a child has a temperature above 101°F (38.5°C). If any meningitis symptoms occur, the child should see a doctor immediately, as early diagnosis and treatment are very important for a successful outcome.

Diagnosis

Viral meningitis often remains undiagnosed because its symptoms are similar to those of the common flu. As for bacterial meningitis, the diagnosis is established by growing bacteria from a sample of spinal fluid. The spinal fluid is obtained by performing a lumbar puncture (also called a spinal tap), in which a needle is inserted into an area in the lower back where fluid in the spinal canal is readily accessible.

Treatment

Bacterial meningitis treatment usually involves intravenous administered antibiotics , for a minimum of four days. The type of meningitis contracted will determine the specific antibiotic used. It is imperative that treatment start as early as possible, in order to avoid brain damage and death.

Viral meningitis cases usually resolve without complications, but typically, antibiotics are ineffective in treating it, so none are prescribed. The child will be told to get as much rest as he or she can. If the child has pain related to the disease such as headaches or other body pains, medication can be used to treat it.

Prognosis

The long-term outlook for children who develop bacterial meningitis varies significantly. The outcome depends on the child's age, the bacteria causing the infection, complications, and the treatment the child receives. The complications of bacterial meningitis can be severe and include neurological problems such as hearing loss, visual impairment, seizures, and learning disabilities. The heart, kidneys, and adrenal glands may also be affected. Although some children develop long-lasting problems, most children who receive prompt diagnosis and treatment recover fully.

The majority of cases of viral meningitis resolve with no complications.

Prevention

Many children as of 2004 routinely receive vaccines against meningitis, starting at about two months of age. Immunizations are recommended by the American Academy of Pediatrics and many other organizations. If a child has not been vaccinated, parents should talk to their doctor about the Hib and pneumococcal (Prevnar 7) vaccines.

KEY TERMS

Analgesics A class of pain-relieving medicines, including aspirin and Tylenol.

Antibody A special protein made by the body's immune system as a defense against foreign material (bacteria, viruses, etc.) that enters the body. It is uniquely designed to attack and neutralize the specific antigen that triggered the immune response.

Antigen A substance (usually a protein) identified as foreign by the body's immune system, triggering the release of antibodies as part of the body's immune response.

Bacterial meningitis Meningitis caused by bacteria. Depending on the type of bacteria responsible for the infection, bacterial meningitis is either classified as monococcal or pneumococcal.

Immunization A process or procedure that protects the body against an infectious disease by stimulating the production of antibodies. A vaccination is a type of immunization.

Meninges The three-layer membranous covering of the brain and spinal cord, composed of the dura mater, arachnoid, and pia mater. It provides protection for the brain and spinal cord, as well as housing many blood vessels and participating in the appropriate flow of cerebrospinal fluid.

Viral meningitis Meningitis caused by a virus. Also called aseptic meningitis.

Vaccines are available for both meningococcal and pneumococcal meningitis. Specifically, there are vaccines against Hib and against some strains of N. meningitidis and many types of Streptococcus pneumoniae. The vaccines against Hib are very safe and highly effective. There is a vaccine that protects against four strains of N. meningitidis, but it is not routinely used in the United States. There are also vaccines to prevent meningitis due to S. pneumoniae, which can also prevent other forms of infection due to S. pneumoniae.

Parents should teach children to wash their hands often, especially before they eat and after using the bathroom, or after petting animals. They should be taught how to wash their hands vigorously, covering both the front and back of each hand with soap and rinsing thoroughly under running water.

Parental concerns

Some forms of bacterial meningitis are contagious. The bacteria are spread through coughing, kissing, and sneezing. Fortunately, the bacteria that cause meningitis are not as contagious as the common cold or the flu, and they are not spread by casual contact or by simply breathing the air where a person with meningitis has been. However, people in the same household or daycare center, or anyone with direct contact with a patient's oral secretions is considered at increased risk of acquiring the infection.

Awareness of the symptoms and signs of meningitis, especially the rash which may accompany meningococcal meningitis is very important.

Resources

BOOKS

Leigh, Jenny. A Dr. Spot Casebook: George Has Meningitis. London: Haldane & Mason, 2003.

Routh, Kristina. Meningitis (Just the Facts). Chicago: Heineman Library, 2004.

Tunkel, Allan R. Bacterial Meningitis. Philadelphia: Lippincott Williams & Wilkins, 2001.

PERIODICALS

Anderson, V., et al. "Cognitive and executive function 12 years after childhood bacterial meningitis: effect of acute neurologic complications and age of onset." Journal of Pediatrics & Psychology 29, no. 2 (March 2004): 6781.

Gupta, S., and A. B. Tuladhar. "Does early administration of dexamethasone improve neurological outcome in children with meningococcal meningitis?" Archives of Disease in Childhood 89, no. 1 (January 2004): 8283.

Hvidd, A., and M. Melhye. "Impact of routine vaccination with a conjugate Haemophilus influenzae type b vaccine." Vaccine 22, no. 34 (January 2004): 37882.

Posfay-Barbe, K. M., and E. R. Wald. "Pneumococcal vaccines: do they prevent infection and how?" Current Opinions in Infectious Diseases 17, no. 3 (June 2004): 17784.

Spach, D. H. "New issues in bacterial meningitis in adults. Antibiotic resistance has complicated treatment." Postgraduate Medicine 114, no. 5 (November 2004): 4350.

ORGANIZATIONS

Meningitis Foundation of America. 6610 North Shadeland Avenue, Suite 200, Indianapolis, IN 462204393. Web site: <www.musa.org>.

National Institute of Allergy and Infectious Diseases (NIAID). National Institutes of Health, 6610 Rockledge Drive, MSC 6612, Bethesda, MD 208926612. Web site: <www.meningitis.org>.

National Meningitis Foundation. 22910 Chestnut Road, Lexington Park, MD 20653. Web site: <www.nmaus.org>.

Meningitis Research Foundation. Midland Way, Thornbury, Bristol BS35 2BS, UK. Web site: <www.meningitis.org>.

WEB SITES

"Meningococcal Disease Homepage." Centers for Disease Control and Prevention. Available online at <www.cdc.gov/ncidod/dbmd/diseaseinfo/meningococcal_g.htm> (accessed October 25, 2004).

Monique Laberge, Ph.D.

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meningitis

meningitis (mĕnĬnjī´tĬs) or cerebrospinal meningitis (sĕr´əbrōspī´nəl), acute inflammation of the meninges, the membranes that cover and protect the brain and spinal cord. It can be caused by bacteria, viruses, fungi, or other organisms, usually introduced via the bloodstream from infections elsewhere in the body.

Viral meningitis

Viral meningitis, sometimes referred to as nonbacterial or aseptic meningitis, is milder and more common than bacterial forms. It can be caused by any of a number of viruses, including enteroviruses, the mumps virus, herpesviruses, HIV, and several mosquito-borne viruses (Bunyavirus and flavivirus) usually associated with encephalitis. Viral meningitis is usually seen only in individual cases rather than in outbreaks. Those not vector-borne are usually spread from person to person by the fecal-oral route. Symptoms include headache, fever, stiff neck, and tiredness, sometimes accompanied by a rash. There is no specific treatment.

Bacterial meningitis

A variety of organisms can cause bacterial meningitis, a serious form that can be fatal, especially in children. Symptoms include high fever, headache, chills, vomiting, stiff neck or back, and confusion, sometimes accompanied by a purplish rash. Serious cases can quickly lead to delirium, coma, or convulsions. It is spread by oral or nasal secretions.

The leading cause of bacterial meningitis is the ill-named bacterium Haemophilus influenzae b (Hib), originally thought to be an influenza virus. It commonly affects infants and children. The second most common bacterial cause of meningitis is Neisseria meningitidis (meningococcus). Meningococcal meningitis affects people of all ages and tends to occur in epidemics, especially among those who live in crowded conditions. An outbreak in the slums of Brazil in 1974–75 killed 11,000 people and left over 75,000 with permanent neurological complications. In 1996–7, an epidemic centered in the Sahel region of W Africa killed 25,000. In the United States it is seen most often in children and teens.

Streptococcus pneumoniae, also referred to as pneumococcus, is another cause of serious meningitis cases. It is the most common cause of meningitis in adults. It often accompanies pneumococcus infections in other parts of the body, such as the ear or sinuses. Other bacterial causes of meningitis include group B streptococcus, tuberculosis, leptospirosis, and Lyme disease.

Bacterial meningitis calls for emergency medical care and the administration of antibiotics. Close contacts of patients with bacterial meningitis may receive prophylactic antibiotics, such as rifampin. Definitive diagnosis can be made by laboratory tests of cerebrospinal fluid obtained by a lumbar puncture (spinal tap). Twenty to thirty percent of children who survive bacterial meningitis sustain permanent neurological damage such as deafness, mental retardation, or convulsions. Since the late 1980s, routine vaccination of young children against Hib has virtually eliminated Hib disease in the United States. Routine vaccination against meningococcal meningitis is recommended for pre-adolescents, and vaccination is also recommended for persons in the military or traveling to parts of Africa where the disease is endemic. The meningococcal vaccine does not provide protection against all meningococcus strains; separate vaccines have been developed against serogroup B meningococcus. Development of an inexpensive meningococcal vaccine for the strain most common in Africa's meningitis belt, which stretches from Senegal and Guinea in the west to Ethiopia in the east, led beginning in 2010 to a mass vaccination drive in the region under the sponsorship of the World Health Organization (WHO) and the Program for Appropriate Technology in Health (PATH).

Fungal meningitis

Fungal meningitis has been on the rise in the United States due to opportunistic infection with Cryptococcus neoformans in people weakened by AIDS. In these patients, it is often fatal. It can be treated with the antifungals amphotericin B and fluconazole. Other causes include coccidioidomycosis and histoplasmosis.

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meningitis

meningitis (men-in-jy-tis) n. an inflammation of the meninges due to viral, bacterial, or fungal infection. Meningitis causes an intense headache, fever, loss of appetite, intolerance to light and sound, rigidity of muscles, especially those in the neck (see also Kernig's sign), and in severe cases convulsions, vomiting, and delirium leading to death. Bacterial meningitis is treated with antibiotics administered as soon as possible after diagnosis. meningococcal m. a serious form of bacterial meningitis, caused by the meningococcus (most importantly, strains B and C), that can lead to widespread infection and meningococcal septicaemia. pneumococcal m. a form of bacterial meningitis caused by the pneumococcus. See also Hib vaccine, meningitis C vaccine, pneumococcal vaccine.
www.meningitis.org Website of the Meningitis Research Foundation

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Meningitis

Meningitis

What Is Meningitis?

How Common Is Meningitis?

How Does Meningitis Spread?

What Are the Signs and Symptoms of Meningitis?

How Is Meningitis Diagnosed and Treated?

What Complications Can Meningitis Cause?

Can Meningitis Be Prevented?

Resources

Meningitis (meh-nin-JY-tis) is an inflammation of the membranes that surround the brain and the spinal cord (the meninges, meh-NIN-jeez). Meningitis is most often caused by infection with a virus or a bacterium.

KEYWORDS

for searching the Internet and other reference sources

Coxsackieviruses

Echoviruses

Enteroviruses

Meninges

Neisseria meningitidis

Streptococcus pneumoniae

Vaccinations

What Is Meningitis?

Meningitis is an inflammation of the meninges, the membranes that enclose and protect the brain and the spinal cord. It is usually caused by infection, most often with viruses or bacteria. Meningitis caused by bacteria is known as septic meningitis. Meningitis caused by other organisms, including viruses, fungi, and parasites, is called aseptic (a-SEP-tik) meningitis. Viral meningitis is the most common and mildest form of the disease, and most people fully recover from it without complications. Bacterial meningitis, if not diagnosed early, can cause serious and sometimes fatal complications.

Enteroviruses, a group of viruses that includes several strains of coxsackieviruses (kok-SAH-kee-vy-ruh-sez) and echoviruses, cause about 90 percent of cases of aseptic meningitis. Two types of bacteria that are most likely to cause septic meningitis are Streptococcus pneumoniae (strep-tuh-KAH-kus nu-MO-nye) and Neisseria meningitidis (nye-SEER-e-uh mehnin-JIH-tih-dis), also called meningococcus (meh-NIN-guh-kah-kus). Before the introduction of a vaccine* in the 1980s to prevent infection with Haemophilus influenzae type b (Hib), the bacterium was a common cause of septic meningitis in young children. Meningitis can be caused by other pathogens* as well, such as some species of parasites and fungi and the bacteria that cause Lyme disease*, tuberculosis*, and syphilis*. Meningitis from these organisms is usually a complication of widespread infection throughout the body and is more likely to be seen in people who have immune problems or other diseases, such as those with AIDS* or cancer. Sometimes, chemical irritations, severe drug allergies, or tumors can lead to inflammation in the central nervous system*, resulting in meningitis.

*vaccine
(vak-SEEN) is a preparation of killed or weakened germs, or a part of a germ or product it produces, given to prevent or lessen the severity of the disease that can result if a person is exposed to the germ itself. Use of vaccines for this purpose is called immunization.
*pathogens
(PAH-tho-jens) are microorganisms that can cause disease in another living organism.
*Lyme
(LIME) disease is a bacterial infection that is spread to humans by the bite of an infected tick. It begins with a distinctive rash and/or flulike symptoms and, in some cases, can progress to a more serious disease with complications affecting other body organs.
*tuberculosis
(too-ber-kyoo-LOsis) is a bacterial infection that primarily attacks the lungs but can spread to other parts of the body.
*syphilis
(SIH-fih-lis) is a sexually transmitted disease that, if untreated, can lead to serious lifelong problems throughout the body, including blindness and paralysis.
*AIDS ,
or acquired immunodeficiency (ih-myoo-no-dih-FIH-shensee) syndrome, is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).
*central nervous system
is the part of the nervous system that includes the brain and spinal cord.

How Common Is Meningitis?

Bacterial meningitis, especially meningococcal meningitis, sometimes occurs in epidemics* in underdeveloped parts of the world, but epidemics are less common in the United States. Because of vaccinations (vak-sih-NAY-shunz) against some of the bacteria that can cause meningitis, the overall number of cases of septic meningitis has steadily declined since 1990. Vaccinated infants and young children are much less likely to contract bacterial meningitis. However, since the late 1990s there has been an increase in the number of cases of meningococcus infection

*epidemics
(eh-pih-DEH-miks) are outbreaks of diseases, especially infectious diseases, in which the number of cases suddenly becomes far greater than usual. Usually, epidemics are outbreaks of diseases in specific regions, whereas worldwide epidemics are called pandemics.

seen in young adults, particularly in college students who live in dormitories.

How Does Meningitis Spread?

Some forms of bacterial meningitis are contagious, but these are not easily spread (compared to germs that cause colds and the flu). Bacterial meningitis almost never results from simply being in the same room or building with someone who has meningitis. Only a small fraction of people who come in contact with these bacteria and viruses will actually develop meningitis.

Bacteria that can cause meningitis are sometimes found in the throats and noses of healthy people. They are spread through direct contact with respiratory secretions (drops of fluid from the mouth, nose, or lungs). This means they can be passed to someone who kisses an infected person or to someone who touches the secretions from someone who is sneezing or coughing and then touches his or her own nose or mouth. Meningococcus can spread in this way through households, daycare centers, and college dormitories.

Enteroviruses commonly are passed from person to person through contact with respiratory secretions, by breathing in drops from someone who is coughing or sneezing, and from contact with an infected persons feces (FEE-seez, or bowel movements).

What Are the Signs and Symptoms of Meningitis?

Symptoms of meningitis often include fever, headache, stiff neck and back, photophobia (painful sensitivity of the eyes to light), abnormal sleepiness, and confusion. Vomiting may also be seen. Infants symptoms are not as specific as those in older children and adults but usually include irritability, lethargy, poor feeding, crying when moved, and vomiting. Infants may not have neck or back stiffness while ill with meningitis. Meningococcus can cause a reddish-purple rash (from bleeding under the skin) that rapidly spreads over the body. Seizures* can occur in anyone with meningitis, regardless of age.

*seizures
(SEE-zhurs) are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements in the body and sometimes a temporary change in consciousness.

How Is Meningitis Diagnosed and Treated?

A doctor will first ask questions about the illness, do a physical examination, and then perform some tests. The brain is sometimes viewed with a computerized tomography* (CT) scan to rule out other reasons for severe headache and illness, such as an abscess*, tumor, or other problems within the brain. A lumbar puncture (also called a spinal tap) is usually done to take a sample of the cerebrospinal (seh-ree-bro-SPY-nuhl) fluid (CSF), the fluid that surrounds the brain and spinal cord. The CSF will be examined under a microscope to look for bacteria or other infectious agents, and increased numbers of white blood cells indicating inflammation.

*computerized tomography
(kom-PYOO-ter-ized toe-MAH-gruh-fee) or CT, also called computerized axial tomography (CAT), is a technique in which a machine takes many X rays of the body to create a three-dimensional picture.
*abscess
(AB-ses) is a localized or walled off accumulation of pus caused by infection that can occur anywhere in the body.

Antibiotics are not used to treat viral meningitis because it is caused by a virus, not bacteria. Once a case of meningitis is known to be viral, rest and pain medication for body aches and headache can help the person feel better until the infection resolves on its own.

Bacterial meningitis requires prompt medical treatment, usually in the hospital. Antibiotics are given to fight the invading organism for at least 2 weeks. Treatment of complications may require intensive care and other medications.

Meningitis that results from other types of infection or other causes is treated with medications, such as antifungal or antiparasitic drugs, and may require hospitalization, especially during the early stages of medical care.

Most cases of viral meningitis last 1 to 2 weeks, and most people recover completely. Symptoms from bacterial meningitis can last weeks, and people may have severe complications from the disease, especially if it is not diagnosed and treated promptly.

What Complications Can Meningitis Cause?

Complications from viral meningitis are not as common as those from bacterial meningitis, but they can include inflammation and swelling of the brain. Sometimes, permanent learning disability and other brain damage can result.

Complications from bacterial meningitis can occur rapidly and be severe, even with quick diagnosis and treatment of the disease. Complications include sepsis*, brain swelling, seizures, shock*, organ failure (such as of the kidneys*), and death. Up to 15 percent of cases of meningitis caused by meningococcus are fatal. Long-term effects are seen in about 10 percent of those who survive bacterial meningitis and can include hearing loss, seizure disorder, learning disabilities, and other problems resulting from brain injury. Meningitis caused by the bacteria that cause tuberculosis is particularly likely to damage the nervous system.

*sepsis
is a potentially serious spreading of infection, usually bacterial, through the bloodstream and body.
*shock
is a serious condition in which blood pressure is very low and not enough blood flows to the bodys organs and tissues. Untreated, shock may result in death.
*kidneys
are the pair of organs that filter blood and remove waste products and excess water from the body in the form of urine.

Can Meningitis Be Prevented?

Vaccinations against Haemophilus influenzae type b and Streptococcus pneumoniae are now given routinely to American children before the age of 2. A vaccine against meningococcus is also available, although it is not regularly used in the United States and is not effective in young children. Young people going off to college, especially those who plan to live in a dormitory, should consider getting the vaccine, as recommended by the U.S. Centers for Disease Control and Prevention and the American Academy of Pediatrics. It also is recommended for people traveling outside the United States, people living in certain institutional settings, the elderly, and people with some chronic* medical conditions.

*chronic
(KRAH-nik) means continuing for a long period of time.

During outbreaks of bacterial meningitis, especially those caused by meningococcus, in schools, dormitories, or daycare people may be given prophylactic* antibiotics to keep the disease from occurring in those who were in close contact with the infected person.

*prophylactic
(pro-fih-LAK-tik) refers to something that is used to prevent an illness or other condition, such as an infection or pregnancy.

It is difficult to keep viruses such as enteroviruses from spreading from person to person. Risk of viral infection can be decreased by washing hands regularly, especially after using the toilet, and avoiding close contact with anyone who is ill, including not sharing food, eating or serving utensils, razors, or other personal items.

See also

AIDS and HIV Infection

Fungal Infections

Lyme Disease

Syphilis

Tuberculosis

Resources

Organizations

Meningitis Foundation of America Inc., 6610 North Shadeland Avenue, Suite 200, Indianapolis, IN 46220. The Meningitis Foundation of America offers information about the disease, including prevention and treatment, at its website.

Telephone 800-668-1129 http://www.musa.org

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC is the U.S. government authority for information about infectious and other diseases. It provides fact sheets about meningitis at its website.

Telephone 800-311-3435 http://www.cdc.gov

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meningitis

men·in·gi·tis / ˌmenənˈjītis/ • n. inflammation of the meninges caused by viral or bacterial infection and marked by intense headache and fever, sensitivity to light, and muscular rigidity, leading (in severe cases) to convulsions, delirium, and death. DERIVATIVES: men·in·git·ic / -ˈjitik/ adj.

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meningitis

meningitis Inflammation of the meninges (membranes) covering the brain and spinal cord, resulting from infection. Bacterial meningitis is more serious than the viral form. Symptoms include headache, fever, nausea and stiffness of the neck. The disease can vary from mild to lethal.

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meningitis

meningitis inflammation of the meninges (enveloping brain and spinal cord). XIX. — modL., f. mēninx, mēning-, Gr. mênigx, pl. mḗnigges; see -ITIS.

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meningitis

meningitis An inflammation of the meninges (the membranes that cover the brain and spinal cord) which may be caused by any of a variety of bacteria or viruses.

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meningitis

meningitisAttis, gratis, lattice •malpractice, practice, practise •Atlantis, mantis •pastis •Lettice, lettuce, Thetis •apprentice, compos mentis, in loco parentis, prentice •Alcestis, testis •poetess • armistice •appendicitis, arthritis, bronchitis, cellulitis, colitis, conjunctivitis, cystitis, dermatitis, encephalitis, gastroenteritis, gingivitis, hepatitis, laryngitis, lymphangitis, meningitis, nephritis, neuritis, osteoarthritis, pericarditis, peritonitis, pharyngitis, sinusitis, tonsillitis •epiglottis, glottis •solstice •mortise, rigor mortis •countess • viscountess •myosotis, notice, Otis •poultice • justice • giantess • clematis •Curtis • interstice • Tethys •Glenrothes • Travis •Jarvis, parvis •clevis, crevice, Nevis •Elvis, pelvis •Avis, Davies, mavis •Leavis • Divis • novice • Clovis •Jervis, service •marquess, marquis

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Meningitis

MENINGITIS

DEFINITION


Meningitis (pronounced meh-nen-JI-tiss) is an inflammation of the meninges (pronounced meh-NIN-jeez). The meninges are the thin layers of tissue that cover the brain and the spinal cord. Meningitis is most commonly caused by infection (by bacteria, viruses, or fungi). It can also be caused by bleeding into the meninges, cancer (see cancer entry), diseases of the immune system, and other factors. The most dangerous forms of meningitis are those caused by bacteria. The disease is very serious and can be fatal.

Meningitis: Words to Know

Blood-brain barrier:
Cells within the blood vessels of the brain that prevent the passage of toxic substances from the blood into the brain.
Cerebrospinal fluid (CSF):
Fluid made in chambers of the brain that flows over the surface of the brain and the spinal cord. CSF provides nutrients to cells of the nervous system and provides a cushion for the structures of the nervous system.
Meninges:
The three-layer membranous covering of the brain and spinal cord.

DESCRIPTION


Any time a part of the body is infected, it is likely to become inflamed and swollen. These symptoms are especially serious in the brain. The brain is enclosed in the skull, a bony structure that cannot change size. If the brain swells, it pushes outward against the skull. Brain cells may become squeezed and begin to die. Brain cells are some of the only kinds of cells in the body that do not regenerate (renew) themselves. Once they die, they cannot be replaced.

An infection in the brain can cause damage in a second way. Brain cells are very delicate. They require just the right balance of chemicals, including sugar, sodium, calcium, potassium, and oxygen. An infection can change the balance of chemicals in the brain. Brain cells may receive too much of one chemical or too little of another. This loss of chemical balance can also kill brain cells.

Meningitis is a serious medical problem because it is difficult to treat. Blood flows into the brain from the neck through a network of blood vessels. This network contains special cells that prevent many chemicals from passing into the brain. This system is known as the blood-brain barrier.

The blood-brain barrier prevents harmful substances from getting into the brain. The blood-brain barrier "knows" which substances the brain needs and which will damage brain cells.

The problem is that the blood-brain barrier usually does not recognize drugs as "good" chemicals. It prevents them from passing into the brain, where they could help clear up an infection. Doctors often have to find other ways to treat the kinds of infection that cause meningitis.

CAUSES


Meningitis may be caused by bacteria, viruses, fungi, head injuries, infections in other parts of the body, and other factors. The type of meningitis a person is most likely to contract depends on his or her age, habits, living environment, and health status.

Bacteria are not the most common cause of meningitis. But they produce the most serious and most life-threatening forms of the disease. The most common kinds of meningitis in newborns are those caused by streptococci (pronounced STREP-tuh-KOK-see) bacteria. These bacteria pass from the mother to the child through the blood system they share before birth. The highest incidence (rate) of meningitis occurs in babies under the age of one month. Children up to the age of two years are also at relatively high risk for the disease.

Adults are usually infected by a different kind of bacterium. This bacterium produces a form of meningitis that has some symptoms like those of pneumonia (see pneumonia entry).

One type of bacterium causes a contagious form of meningitis. A person with this form of meningitis can pass it to others with whom he or she comes into contact. Epidemics (mass infections) of meningitis have been known to occur in crowded day-care centers and military training camps.

Meningitis is often caused by a virus. The virus is usually the same one that causes other viral infections such as mumps (see mumps entry), measles (see measles entry), chickenpox (see chickenpox entry), rabies (see rabies entry), and herpes infections (like cold sores; see herpes infections entry).

A person's general health can also increase his or her risk of developing meningitis. For example, a person with a weakened immune system is at greater risk for meningitis than one who has a healthy immune system. People with AIDS (see AIDS entry) have damaged immune systems and are less able to fight off fungal infections. These fungal infections can lead to infections of the brain and meningitis.

People who have had their spleens removed are also at higher risk for meningitis. Spleen removal may be necessary to solve some other medical problem, such as cancer of the spleen. But it may also expose the patient to greater risk for meningitis.

The most common cause of meningitis is blood-borne spread. This term means that a person already has an infection in some other part of his or her body. If that infection is not treated properly, it can become more serious and start to spread through the body by way of the bloodstream. Normally, the blood-brain barrier would keep the infectious agents out of the brain. But if huge numbers of infectious agents accumulate in the blood, some of them may get through the blood-brain barrier. They will then be able to infect the meninges and cause meningitis. Infections that occur close to the brain, such as an ear or sinus infection, pose an especially high risk for meningitis.

Meningitis can also develop because of openings in the skull. These openings can occur because of a skull fracture or a surgical procedure. These openings provide a way for infectious agents to get into the brain because the blood-brain barrier cannot prevent the infection.

SYMPTOMS


The classic symptoms of meningitis include fever, headache, vomiting, sensitivity to light, irritability, severe fatigue, stiff neck, and a reddish-purple rash on the skin. If the infection is not treated quickly, more serious symptoms develop, including seizures, confusion, and coma.

SARA ELIZABETH BRANHAM

Before the discovery of antibiotics, meningitis was a dreaded diseases. There was no way to stop its progress. Those who survived an attack of the disease were likely to be left blind, deaf, or mentally retarded. The disease was also feared because of the ease with which it spread. During World War I (191418), for example, meningitis often swept through groups of soldiers who lived and fought together. The only way to stop its spread was to isolate infected soldiers from others who were still healthy.

Important breakthroughs in the treatment of meningitis came as the result of the work of Dr. Sara Elizabeth Branham (18881962). Dr. Branham worked for many years at the National Institutes of Health. Initially, she was interested primarily in food poisoning caused by bacteria. But the tragedies of World War I encouraged her to focus on ways of treating meningitis.

When she began her research, the only treatment available for meningitis was antiserum obtained from horses. Horse antiserum is a chemical produced in horses when they have been exposed to meningitis bacteria. As horse antiserum lost its effectiveness, Dr. Branham developed another form of antiserum, produced in rabbits.

Finally, in 1937, Dr. Branham decided to try the newly discovered sulfonamide drugs on meningitis. The sulfonamides were the first antibiotics to be widely used. Dr. Branham found that they could be used effectively against the bacteria that cause meningitis. Largely as a result of her research, meningitis was kept under control during World War II (193945).

These symptoms may not be present in very young babies or the elderly. The immune system of babies is usually not developed enough to fight off an infection of the meninges. So symptoms that accompany an immune response, such as fever, are not observed. Seizures may be the only symptom of meningitis in young children. The same is true of older people who have other kinds of medical disorders that leave them in a weakened state.

DIAGNOSIS


The first clues that a person may have meningitis can be obtained from a simple physical examination. The doctor may try to move the patient's head in various directions. For a person with meningitis, these movements can be difficult and painful.

The standard test for diagnosing meningitis is called a lumbar puncture (LP), or spinal tap. An LP involves the insertion of a thin needle into the space between the vertebrae that make up the spine. A small sample of cerebrospinal fluid is removed. Cerebrospinal fluid (CSF) is a clear liquid present in the space between cells in the brain and the spinal cord. It serves a number of important functions. It provides a cushion for the brain and spinal cord, brings nutrients to these structures, and carries away waste products.

CSF normally contains certain fixed amounts of various chemicals, such as sugar, sodium, potassium, and calcium. An infection in the meninges will cause a change in these amounts. For example, bacteria "eat" sugar, so the presence of bacteria in the meninges causes a reduction in the amount of sugar in the CSF.

The presence of white blood cells in the CSF is also a clue to the presence of meningitis. The immune system produces white blood cells to fight off infections. A healthy body would normally not have white blood cells in the CSF. If they are present, the immune system is probably fighting an infection in the brain or spinal cord, such as meningitis.

TREATMENT


Meningitis infections caused by bacteria can be treated with antibiotics. Penicillin and cephalosporins (pronounced seff-a-lo-SPORE-inz) are commonly used. Special methods are necessary for giving these drugs, however, because of the blood-brain barrier. The usual procedure is to inject large quantities of an antibiotic directly into a person's bloodstream. If the concentration of drugs is high enough, some will get through the blood-brain barrier and into the meninges.

Antiviral and antifungal medications can be used similarly. Antiviral drugs usually do not kill viruses, but they can lessen some of the effects of the viruses.

Steroids may also be used to treat meningitis. Steroids tend to reduce inflammation and swelling, lessening possible harm to brain cells. The balance of sugar, sodium, potassium, calcium, and other substances in the CSF must also be carefully monitored. It may be necessary to inject one or more of these chemicals into the patient's body to maintain a proper balance.

PROGNOSIS


Viral meningitis is the least severe type of the disease. Patients usually recover with no long-term effects. Bacterial infections are far more serious and progress quickly. Very rapid treatment with antibiotics is necessary. If the infection is not halted, the patient may fall into a coma and die in less than a day.

Death rates for meningitis vary depending on the cause of the infection. Overall, the death rate from the disease is just less than 20 percent.

Long-term effects of meningitis are not unusual. For example, damage to cells in certain parts of the brain can cause deafness and/or blindness. Some patients develop permanent seizure disorders. These disorders may require lifelong treatment with antiseizure medications. Scarring of brain tissue can block normal flow of CSF. This condition may be serious enough to require the installation of shunt tubes, surgically implanted devices that help to restore normal circulation of CSF.

PREVENTION


There are no specific recommendations for avoiding meningitis. People should try to avoid developing any kind of infection that might spread to the meninges, especially those of the ear and sinus.

Some preventive treatments are available for specific types of meningitis. For example, there is a vaccine for individuals who have to be in areas where contagious meningitis exists. These individuals may also take antibiotics to protect them from infection by the bacterium that causes this form of the disease. A vaccine is available for one of the forms of meningitis that occurs in young children.

FOR MORE INFORMATION


Books

Stoffman, Phyllis. The Family Guide to Preventing and Treating 100 Infectious Diseases. New York: John Wiley & Sons, 1995.

Willett, Edward. Meningitis. Hillside, NJ: Enslow Publishers, Inc. 1999.

Periodicals

Meissner, Judith W. "Caring for Patients with Meningitis." Nursing (July 1995): pp. 50+.

Organizations

American Academy of Neurology. 1080 Montreal Avenue, St. Paul, MN 55116. (612) 695-1940. http://www.aan.com.

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Meningitis

Meningitis

Definition

Meningitis is a potentially fatal inflammation of the meninges, the thin, membranous covering of the brain and the spinal cord. Meningitis is most commonly caused by infection (bacteria, viruses, or fungi ), although it can also be caused by bleeding into the meninges, cancer, diseases of the immune system, and an inflammatory response to certain types of chemotherapy or other chemical agents. The most serious and difficult-to-treat types of meningitis tend to be those caused by bacteria.

Description

Meningitis is a particularly dangerous infection because of the very delicate nature of the brain. Brain cells are among a very small number of cells in the body that, once killed, will not regenerate. Therefore, if enough brain tissue is damaged, serious, life-long handicaps may remain.

To understand meningitis, it is important to have a basic understanding of the anatomy of the brain. The meninges are three separate membranes layered together that encase the brain and spinal cord:

  • The dura is the toughest, outermost layer, and is closely attached to the inside of the skull.
  • The arachnoid, the middle layer, is important because of its involvement in the normal flow of the cerebrospinal fluid (CSF), a lubricating and nutritive fluid that bathes both the brain and the spinal cord.
  • The pia, the innermost layer, helps direct blood vessels into the brain.

The space between the arachnoid and the pia contains CSF, which helps insulate the brain from trauma. Many blood vessels course through this space.

CSF, produced within specialized chambers deep inside the brain, flows over the surface of the brain and spinal cord. This fluid serves to cushion these relatively delicate structures, as well as to supply important nutrients for brain cells. CSF is reabsorbed by blood vessels located within the meninges. A careful balance between CSF production and reabsorption is important to avoid the accumulation of too much CSF.

Because the brain is enclosed in the hard, bony case of the skull, any disease that produces swelling of the brain will be damaging. The skull cannot expand at all; so, when any swollen brain tissue pushes up against the skull's hard bone, brain tissue may become damaged and ultimately die. Swelling on one side of the brain will not only cause pressure and damage to that side of the brain, but, because it takes up precious space within the tight confines of the skull, the opposite side of the brain will also be pushed against the skull, causing damage to that side also.

Another way that infections injure the brain involves the way the chemical environment of the brain changes in response to that infection. Brain cells require a very well-regulated environment. Careful balance of oxygen, carbon dioxide, sugar (glucose), sodium, calcium, potassium, and other substances must be maintained to avoid damage to brain tissue. An infection upsets this balance. Brain damage can occur when cells are either deprived of important nutrients or exposed to toxic levels of particular substances.

The cells lining the brain's tiny blood vessels (capillaries) are specifically designed to prevent many substances from passing into brain tissue. This is commonly referred to as the blood-brain barrier. The blood-brain barrier prevents various substances that could be harmful to brain tissue (toxins), as well as many agents of infection, from crossing from the blood stream into the brain tissue. While this barrier is obviously an important protective feature for the brain, it also serves to complicate treatment in the case of an infection by making it difficult for medications to pass out of the blood and into the brain tissue where an infection is located.

Causes and symptoms

The most common infectious causes of meningitis vary according to an individual's age, habits, living environment, and health status. While nonbacterial types of meningitis are most common, bacterial meningitis is the more potentially life threatening. Three bacterial agents are responsible for about 80% of all bacterial meningitis cases. These bacteria are Haemophilus influenzae type b, Neisseria meningitidis (causing meningococcal meningitis), and Streptococcus pneumoniae (causing pneumococcal meningitis).

In newborns, the most common agents of meningitis are those contracted from the newborn's mother, including Group B streptococci (which is becoming an increasingly common infecting organism in the new-born period), Escherichia coli, and Listeria monocytogenes. The highest incidence of meningitis occurs in babies younger than a month old, with an increased risk of meningitis continuing through about two years of age.

Older children are more frequently infected by the bacteria Haemophilus influenzae, Neisseria meningitidis, and Streptococci pneumoniae.

Adults are most commonly infected by either S. pneumoniae or N. meningitidis, with pneumococcal meningitis the most common. Certain conditions predispose an individual to this type of meningitis, including alcoholism and chronic upper respiratory tract infections (especially of the middle ear, sinuses, and mastoids).

N. meningitidis is the only organism that can cause epidemics of meningitis. In particular, these appear to occur when a child in a crowded day-care situation, or a military recruit in a crowded training camp, has fallen ill with meningococcal meningitis.

Viral causes of meningitis include the herpes simplex virus, the mumps and measles viruses (against which most children are protected due to mass immunization programs), the virus that causes chicken pox, the rabies virus, and a number of viruses that are acquired through the bites of infected mosquitoes.

A number of medical conditions predispose individuals to meningitis caused by specific organisms. People with AIDS (acquired immunodeficiency syndrome) are more prone to getting meningitis from fungi, as well as from the agent that causes tuberculosis. Persons who have had their spleens removed, or whose spleens are no longer functional (as in the case of individuals with sickle cell disease ) are more susceptible to meningococcal and pneumococcal meningitis.

The majority of meningitis infections are acquired by blood-borne spread. A person may have another type of infection (of the lungs, throat, or tissues of the heart ) caused by an organism that can also cause meningitis. If this initial infection is not properly treated, the organism will continue to multiply, find its way into the blood stream, and be delivered in sufficient quantities to pass the blood brain barrier. Direct spread occurs when an organism spreads to the meninges from infected tissue next to or very near the meninges. This can occur, for example, with a severe, poorly treated ear or sinus infection.

Persons who suffer from skull fractures possess abnormal openings to the sinuses, nasal passages, and middle ears. Organisms that usually live in the human respiratory system without causing disease can pass through such openings, reach the meninges, and cause infection. Similarly, people who undergo surgical procedures or who have had foreign bodies surgically placed within their skulls (such as tubes to drain abnormal amounts of accumulated CSF) have an increased risk of meningitis.

Organisms can also reach the meninges via an uncommon but interesting method called intraneural spread. This involves an organism invading the body at a considerable distance away from the head, spreading along a nerve, and using that nerve as a ladder into the skull where the organism can multiply and cause meningitis. Herpes simplex virus is known to use this type of spread, as is the rabies virus.

The most classic symptoms of meningitis (particularly of bacterial meningitis) include fever, headache, vomiting, sensitivity to light (photophobia), irritability, severe fatigue (lethargy), stiff neck, and a reddish purple rash on the skin. Untreated, the disease progresses with seizures, confusion, and eventually coma.

A very young infant may not show the classic signs of meningitis. Early in infancy, a baby's immune system is not yet developed enough to mount a fever in response to infection, so fever may be absent. In some infants with meningitis, seizures are the only identifiable symptom. Similarly, debilitated elderly people may not have fever or other identifiable symptoms of meningitis.

Brain damage due to meningitis occurs from a variety of phenomena. The action of infectious agents on the brain tissue is one direct cause of damage. Other types of damage may be due to the mechanical effects of swelling and compression of brain tissue against the skull. Swelling of the meninges may interfere with the normal absorption of CSF by blood vessels, causing accumulation of CSF and damage from the resulting pressure on the brain. Interference with the brain's carefully regulated chemical environment may cause abnormal and damaging amounts of normally present substances (carbon dioxide, potassium) to accumulate. Inflammation may cause the blood-brain barrier to become less effective at preventing the passage of toxic substances into brain tissue.

Diagnosis

A number of techniques are used when examining a person suspected of having meningitis to verify the diagnosis. Certain manipulations of the head (lowering the head, chin towards chest, for example) are difficult to perform and painful for a person with meningitis.

The most important test used to diagnose meningitis is the lumbar puncture (commonly called a spinal tap). Lumbar puncture (LP) involves the insertion of a thin needle into a space between the vertebrae in the lower back and the withdrawal of a small amount of CSF. The CSF is then examined under a microscope to look for bacteria or fungi. Normal CSF contains set percentages of glucose and protein. These percentages will vary with bacterial, viral, or other causes of meningitis. For example, bacterial meningitis causes a greatly decreased percentage of glucose in the CSF because the bacteria are essentially consuming or "eating" that glucose and using it for their own nutrition and energy production. Normal CSF should contain no infection-fighting cells (white blood cells), so the presence of white blood cells in CSF is another indication of meningitis. Some of the withdrawn CSF is put into special lab dishes to allow growth of the infecting organism, which can then be identified more easily. Special immunologic and serologic tests may also be used to help identify the infectious agent.

In rare instances a lumbar puncture cannot be performed because of the amount of swelling and pressure within the skull (intracranial pressure). This pressure is measured immediately upon insertion of an LP needle. If it is found to be high, no fluid is withdrawn because doing so could cause herniation of the brain stem. Herniation of the brain stem occurs when the part of the brain connecting to the spinal cord is thrust through the opening at the base of the skull into the spinal canal. Such herniation will cause compression of those structures within the brain stem that control the most vital functions of the body (breathing, heart beat, consciousness). Death or permanent debilitation follows herniation of the brain stem.

Treatment

Antibiotic medications (forms of penicillin and cephalosporins, for example) are the most important elements of treatment against bacterial meningitis. Because of the effectiveness of the blood-brain barrier in preventing passage of substances into the brain, medications must be delivered directly into an affected person's veins (intravenously, or IV), at very high doses. Antiviral drugs (acyclovir) may be helpful in shortening the duration of viral meningitis, and antifungal medications are also available.

Other treatments involve decreasing inflammation (with steroid preparations) and paying careful attention to the balance of fluids, glucose, sodium, potassium, oxygen, and carbon dioxide in a person's system. People who develop seizures will require medications to halt the seizures and prevent their return.

Prognosis

Viral meningitis is the least severe type, and persons usually recover with no long-term effects from the infection. Bacterial infections, however, are much more severe, and rapidly progress. Without very rapid treatment with the appropriate antibiotic, an infection can swiftly lead to coma and death, often in less than 24 hours. While death rates from meningitis vary depending upon the specific infecting organism, the overall death rate is just under 20%.

The most frequent long-term effects of meningitis include deafness and blindness, which may be caused by the compression of specific nerves and brain areas responsible for the senses of hearing and sight. Some people develop permanent seizure disorders, requiring life-long treatment with antiseizure medications. Scarring of the meninges may result in obstruction of the normal flow of CSF, causing abnormal accumulation of CSF. This may be a chronic problem for some people, requiring the installation of shunt tubes to drain the accumulation on a regular basis.

Health care team roles

Family physicians, pediatricians, emergency physicians, or internists usually make the initial diagnosis of meningitis. Laboratory technicians identify organisms that cause meningitis. Nurses and other hospital staff provide supportive care, and patient and family education. Occasionally, physical therapists are needed to help the patient recover lost muscle functioning.

KEY TERMS

Arachnoid mater— The middle layer of the meninges.

Blood-brain barrier— An arrangement of cells within the blood vessels of the brain that prevents toxic substances, infectious agents, and many medications, from passing from the blood into the brain.

Cerebrospinal fluid (CSF)— Fluid made in chambers within the brain which then flows over the surface of the brain and spinal cord. CSF provides nutrition to cells of the nervous system, as well as providing a cushion for the nervous system structures.

Dura mater The outermost layer of the meninges.

Lumbar puncture (LP)— A medical test in which a very narrow needle is inserted into a specific space between the vertebrae of the lower back in order to obtain a sample of CSF for examination.

Meninges— The three-layer membranous covering of the brain and spinal cord, composed of the dura, arachnoid, and pia. It provides protection for the brain and spinal cord, as well as housing many blood vessels and participating in the appropriate flow of CSF.

Photophobia— Abnormal sensitivity to light.

Pia mater— The innermost layer of the meninges.

Prevention

Prevention of meningitis primarily involves the appropriate treatment of other infections an individual may acquire, particularly those known to seed to the meninges (such as ear and sinus infections). Preventive treatment with antibiotics is sometimes recommended for those in close contacts with an individual who is ill with meningococcal or H. influenzaetype b meningitis. A meningococcal vaccine is sometimes recommended to individuals traveling to very high risk areas. A vaccine for H. influenzae type b is now given to babies as part of the standard array of childhood immunizations.

Resources

BOOKS

Adams, Raymond D, Maurice Victor, and Allan H. Ropper. Adam's & Victor's Principles of Neurology, 6th ed. New York: McGraw Hill, 1997.

Koroshetz, Walter J, and Morton N. Swartz. "Chronic and Rrecurrent Meniingitis." In Harrison's Principles of Internal Medicine, 14th ed. Ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2434-2439.

Nath, Avindra, and Joseph R. Berger. "Acute Viral Meningitis and Encephalitis." In Cecil Textbook of Medicine, 21st ed. Ed. Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, 2123-2126.

Pollard, Andrew J., and Martin C. J. Maiden. Meningococcal Disease: Methods and Protocols. Totowa: Humana Press, 2001.

Prober, Charles G. "Acute Bacterial Meningitis Beyond the Neonatal Period." In Nelson Textbook of Pediatrics 16th ed. Ed. Richard E. Behrman et al., Philadelphia: Saunders, 2000, 751-757.

――――――. "Eosinophilic Meningitis." In Nelson Textbook of Pediatrics 16th ed. Ed. Richard E. Behrman et al., Philadelphia: Saunders, 2000, 760-761.

――――――. "Viral Meningoencephalitis." In Nelson Textbook of Pediatrics 16th ed. Ed. Richard E. Behrman et al., Philadelphia: Saunders, 2000, 757-760.

Scheld, W. Michael. "Bacterial Meningitis, Brain Abscess, and Other Suppurative Intracranial Infections." In Harrison's Principles of Internal Medicine 14th ed. Ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2419-2434.

Tyler, Kenneth L. "Aseptic Meningitis, Viral Encephalitis, and Prion Diseases." In Harrison's Principles of Internal Medicine 14th ed. Ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2451-2457.

PERIODICALS

Agarwal, R., and A. J. Emmerson. "Should Repeat Lumbar Punctures be Routinely Done in Neonates with Bacterial Meningitis? Results of a Survey into Clinical Practice." Archives of Diseases of Children 84, no. 5 (2001): 451-452.

Colby, C. E., W. J. Steinbach, and A. K. Haiman. "A 10-week Old Infant with Meningitis." Clinics in Pediatrics 40, no. 3 (2001): 155-158.

Glennie, L. "Meningitis: A Rash Diagnosis." Nursing Times 96, no. 12 (2000): 44-45.

Kerr, C. "Meningitis Hits West Africa." Trends in Microbiology 9, no. 5 (2001): 203-205.

van den Berg, H., M. van der Flier, and M. D. van de Wetering. "Cytarabine-Induced Aseptic Meningitis." Leukemia 15, no. 4 (2001): 697-699.

von Vigier, R. O., S. M. Colombo, P. B. Stoffel, P. Meregalli, A. C. Truttmann, and M. G. Bianchetti. "Circulating Sodium in Acute Meningitis." American Journal of Nephrology 21. no. 2 (2001): 87-90.

ORGANIZATIONS

American Academy of Emergency Medicine. 611 East Wells Street, Milwaukee, WI 53202. (800) 884-2236. 〈http://www.aaem.org〉.

Meningitis Foundation of America Inc. 7155 Shadeland Station, Suite 190, Indianapolis, Indiana 46256-3922. (800) 668-1129 or (317) 595-6383. 〈http://www.musa.org/default.htm〉.

OTHER

American Academy of Family Practice. 〈http://www.aafp.org/afp/990515ap/2761.html.,〉 and 〈http://www.aafp.org/afp/971001ap/tunkel.html〉.

Association of State and Territorial Directors of Health Promotion and Public Health Education. 〈http://www.astdhpphe.org/infect/bacmeningitis.html〉.

Centers for Disease Control and Prevention. 〈http://www.cdc.gov/od/oc/media/pressrel/r991021.htm.,〉 and 〈http://www.cdc.gov/ncidod/dbmd/diseaseinfo/meningococcal_g.htm〉.

Meningitis Research Foundation of UK. 〈http://www.meningitis.org.uk〉.

National Institute for Medical Research (UK). 〈http://www.nimr.mrc.ac.uk/MillHillEssays/1999/meningitis.htm〉.

National Institute of Neurological Disorders and Stroke. 〈http://www.ninds.nih.gov/health_and_medical/disorders/encmenin_doc.htm〉.

National Library of Medicine. 〈http://www.nlm.nih.gov/medlineplus/meningitis.html〉.

National Meningitis Trust of UK. 〈http://www.meningitis-trust.org.uk/frame.htm〉.

University of Illinois School of Medicine. 〈http://www.mckinley.uiuc.edu/health-info/dis-cond/commdis/meningit.html〉.

University of Maryland College of Medicine. 〈http://umm.drkoop.com/conditions/ency/article/000680.htm〉.

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Meningitis

Meningitis

History

Anatomical considerations

Infectious causes of meningitis

How the infectious agents of meningitis gain access to the meninges

Symptoms of meningitis

How meningitis damages the brain

Long term complications of meningitis

Diagnosis

Treatment

Prevention

Resources

Meningitis is a potentially fatal inflammation of the meninges, the thin, membranous covering of the brain and the spinal cord. Meningitis is most commonly caused by infection (by bacteria, viruses, or fungi), although it can also be caused by bleeding into the meninges, cancer, or diseases of the immune system.

History

Before antibiotics were available, bacterial meningitis was a dreaded disease, taking a toll on the young and leaving those who survived blind, deaf, or mentally retarded. A pioneer in the research of this disease and its cure was Dr. Sara Elizabeth Branham (18881962), who worked at the National Institute of Health in the early part of the twentieth century. Initially, she performed research on bacterially caused food poisoning; but after the epidemic years of World War I (19141918), she worked on the specific antiserum to combat meningitis. During World War I, cases of the disease ran rampant among soldiers, often leading to lengthy quarantines to prevent its further spread. Knowing that many strains of infectious bacteria could be responsible, Branham developed laboratory procedures that enabled technicians to determine which type of infection was present. At that time, the only treatment for meningitis was an antiserum (developed from horses) that had been losing its effectiveness over the years. Branham substituted a more effective serum extracted from rabbits. In 1937, Branham and a coworker discovered that the newly developed sulfonamide drugs (sulfonamides) were effective in treating meningitis. Sulfadiazine was then used along with antiserum as an effective treatment and was responsible for keeping meningitis at bay during World War II (19391945). Branham wrote widely about the disease and was recognized for her dedicated work with awards and honorary degrees.

Anatomical considerations

The meninges are three separate membranes, layered together, which serve to encase the brain and spinal cord. The dura is the toughest, outermost layer, and is closely attached to the inside of the skull. The middle layer, the arachnoid, is important in the normal flow of the cerebrospinal fluid (CSF), a lubricating fluid that bathes both the brain and the spinal cord. The innermost layer, the pia, helps direct brain blood vessels into the brain. The space between the arachnoid and the pia contains CSF, which serves to help insulate the brain from trauma. Through this space course many blood vessels.

CSF, produced within specialized chambers deep inside the brain, flows over the surface of the brain and spinal cord. This fluid serves to cushion these relatively delicate structures, as well as supplying important nutrients for brain cells. CSF is reabsorbed by blood vessels which are located within the meninges.

Because the brain is enclosed in the hard, bony case of the skull, any disease process that produces swelling will ultimately prove destructive to the brain. The skull cannot expand at all, so when swollen brain tissue pushes up against the skulls hard bone, the brain tissue becomes damaged and may ultimately die. Furthermore, swelling on the right side of the brain will not only cause pressure and damage to that side of the brain, but by taking up precious space within the tight confines of the skull, the left side of the brain will also be pushed up against the hard surface of the skull. This action causes reciprocal damage to that side of the brain as well.

The cells of the brain require a very well-regulated environment for optimal function. Careful balance of oxygen, carbon dioxide, glucose (sugar), sodium, calcium, potassium, and other substances must be maintained in order to avoid damage to the relatively unforgiving brain tissue.

The cells lining the brains capillaries (tiny blood vessels) are specifically designed to prevent many substances from passing into brain tissue. This is commonly referred to as the blood-brain barrier. The blood-brain barrier prevents various toxins (substances which could be poisonous to brain tissue), as well as many agents of infection, from crossing from the blood stream into the brain tissue. While this barrier obviously is an important protective feature for the brain, it also serves to complicate therapy in the case of an infection, by making it difficult for medications to pass out of the blood and into the brain tissue where the infection resides.

Infectious causes of meningitis

The most common infectious causes of meningitis vary according to an individual hosts age, habits and living environment, and health status. In newborns, the most common agents of meningitis are those which are contracted from the newborns mother, including Group B streptococci (becoming an increasingly common infecting organism in the newborn period), Escherichia coli, and Listeria monocytogenes. Older children are more frequently infected by Haemophilus influenzae, Neisseria meningitidis, and Streptococcus pneumoniae, while adults are infected by S. pneumoniae and N. meningitidis. N. meningitidis is the only organism that can cause epidemics of meningitis. These have occurred in particular when a child in a crowded day-care situation or a military recruit in a crowded training camp has fallen ill with N. meningitidis meningitis.

Viral causes of meningitis include the herpes simplex viruses, mumps and measles viruses (against which most children are protected due to mass immunization programs), the virus that causes chicken pox, the rabies virus, and a number of viruses that are acquired through the bite of infected mosquitoes. Patients with AIDS (acquired immune deficiency syndrome) are more susceptible to certain infectious causes of meningitis, including by certain fungal agents, as well as by the agent that causes tuberculosis. Patients who have had their spleens removed, or whose spleens are no longer functional (as in the case of patients with sickle cell disease) are more susceptible to certain infections, including those caused by N. meningitidis and S. pneumoniae.

How the infectious agents of meningitis gain access to the meninges

The majority of meningitis infections are acquired by blood-borne spread. An individual may have another type of infection (of the lungs, throat, or tissues of the heart) caused by an organism that can also cause meningitis. The organism multiplies, finds its way into the blood stream, and is delivered in sufficient quantities to invade past the blood-brain barrier.

Direct spread occurs when an already resident infectious agent spreads from infected tissue next to or very near the meninges, for example from an ear or sinus infection. Patients who suffer from skull fractures provide openings to the sinuses, nasal passages, and middle ears. Organisms that frequently live in the human respiratory system can then pass through these openings to reach the meninges and cause infection. Similarly, patients who undergo surgical procedures or who have had foreign bodies surgically placed within their skulls (such as tubes to drain abnormal amounts of accumulated CSF) have an increased risk of the organisms causing meningitis being introduced to the meninges.

The least common method by which the organisms causing meningitis are transmitted, but one of the most interesting, is called intraneural spread. This involves an organism spreading along a nerve, and using that nerve as a kind of ladder into the skull where the organism can multiply and cause meningitis. Herpes simplex virus is known to use this type of spread, as is the rabies virus.

Symptoms of meningitis

The most classic symptoms of meningitis (particularly of bacterial meningitis) include fever, headache, vomiting, photophobia (sensitivity to light), irritability, lethargy (severe fatigue), and stiff neck. The disease progresses with seizures, confusion, and eventually coma.

A young infant may not show the classic signs of meningitis. Early in infancy, a babys immune system is not yet developed enough to mount a fever in response to infection, so fever may be absent. Some infants with meningitis have seizures as their only identifiable symptom.

How meningitis damages the brain

Damage due to meningitis occurs from a variety of phenomena. The action of infectious agents on the brain tissue is one direct cause of damage. Other types of damage may be due to mechanical effects of swelling of brain tissue, and compression against the bony surface of the skull. Swelling of the meninges may interfere with the normal absorption of CSF by blood vessels, causing accumulation of CSF and damage due to resulting pressure on the brain. Interference with the brains carefully regulated chemical environment may cause damaging amounts of normally present substances (carbon dioxide, potassium) to accumulate. Inflammation may cause the blood-brain barrier to become less effective at preventing the passage of toxic substances into brain tissue.

Long term complications of meningitis

The most frequent long-term effects of meningitis include deafness and blindness, due to compression of specific nerves and brain areas responsible for the senses of hearing and sight. Some patients develop permanent seizure disorders, requiring lifetime treatment with anti-seizure medications. Scarring of the meninges may result in obstruction of the normal flow of CSF, causing abnormal accumulation of CSF. This may be a chronic problem for some patients, requiring the installation of tubes to regularly drain the accumulation.

Diagnosis

A number of techniques are used when examining a patient suspected of having meningitis to verify the diagnosis. Certain manipulations of the head (lowering the head, chin towards chest, for example) are difficult to perform and painful for a patient with meningitis.

The most important test used to diagnosis meningitis is the lumbar puncture (commonly called a spinal tap). Lumbar puncture (LP) involves the insertion of a thin needle into a space between the vertebrae in the lower back, and the withdrawal of a small amount of CSF. The CSF is then examined under a microscope. Normal CSF contains set percentages of glucose and protein. These percentages will vary with bacterial, viral, or other causes of meningitis. For example, bacterial meningitis causes a greatly lower than normal percentage of glucose to be present in CSF, as the bacteria are essentially eating the hosts glucose, and using it for their own nutrition and energy production. Normal CSF should contain no white blood cells (infection fighting cells), so the presence of white blood cells in CSF is another indication of meningitis. Some of the withdrawn CSF is also put into special laboratory dishes to allow growth of the infecting organism, which can then be identified more easily.

In a few rare instances, lumbar puncture cannot be performed, because the amount of swelling within the skull is so great that the intracranial pressure (pressure within the skull) is extremely high. This pressure is always measured immediately upon insertion of the LP needle. If it is found to be very high, no fluid is withdrawn, because withdrawal of fluid could cause herniation of the brain stem. Herniation of the brain stem occurs when the part of the brain connecting to the spinal cord is thrust through the opening at the base of the skull into the spinal canal. Such herniation will cause compression of those structures within the brain stem that control the most vital functions of the body (breathing, heartbeat, consciousness). Death or permanent debilitation follows herniation of the brain stem.

Treatment

Antibiotic medications (forms of penicillins and cephalosporins, for example) are the most important element of treatment against bacterial agents of meningitis. Because of the effectiveness of the blood-brain barrier in preventing passage of substances into the brain, medications must be delivered directly into the patients veins (intravenous or IV) at very high doses. Antiviral medications (acyclovir) may be helpful in the case of viral meningitis, and antifungal medications are available as well.

Other treatment for meningitis involves decreasing inflammation (with steroid preparations) and paying careful attention to the balance of fluids, glucose, sodium, potassium, oxygen, and carbon dioxide in the patients system. Patients who develop seizures will require medications to halt the seizures and prevent their return.

KEY TERMS

Blood-brain barrier A blockade of cells separating the circulating blood from elements of the central nervous system (CNS); it acts as a filter, preventing many substances from entering the central nervous system.

Cerebrospinal fluid (also called CSF) Fluid made in chambers within the brain; this fluid then flows over the surface of the brain and spinal cord, providing nutrition to cells of the nervous system, as well as cushioning.

Lumbar puncture (also called LP) A medical test in which a very narrow needle is inserted into a specific space between the vertebrae of the lower back in order to draw off and examine a sample of CSF.

Meninges The three layer membranous covering of the brain and spinal cord, composed of the dura, arachnoid, and pia. Provides protection for the brain, as well as housing many blood vessels.

Prevention

A series of vaccines against Haemophilus influenzae, started at two months of age, has greatly reduced the incidence of that form of meningitis. Vaccines also exist against Neisseria meningitidis and Streptococcus pneumoniae bacteria, but these vaccines are only recommended for those people who have particular susceptibility to those organisms, due to certain immune deficiencies, lack of a spleen, or sickle cell anemia.

Because N. meningitidis is known to cause epidemics of disease, close contacts of patients with such meningitis (other children in day care with the patient, other military personnel within the same training camp, and people living within the patients household), are treated with Rifampin® (or rifampicin). This generally prevents spread of the disease.

Mothers with certain risk factors may be treated with antibiotics during labor, to prevent the passage of certain organisms which may cause meningitis in the newborn (particularly Group B streptococcus).

Resources

BOOKS

Andreoli, Thomas E., et al. Cecil Essentials of Medicine. Philadelphia: W.B. Saunders Company, 2004.

Cormican, M.G. and M.A. Pfaller. Molecular Pathology of Infectious Diseases, in Clinical Diagnosis and Management by Laboratory Methods. 20th ed. Philadelphia: W. B. Saunders, 2001.

Janner, Donald. A Clinical Guide to Pediatric Infectious Disease. Philadelphia, PA: Lippincott Williams & Wilkins, 2005.

Kasper, Dennis L., et al. Harrisons Principles of Internal Medicine. New York: McGraw Hill, Medical Pub. Division, 2005.

Kobayashi, G., Patrick R. Murray, Ken Rosenthal, and Michael Pfaller. Medical Microbiology. St. Louis, MO: Mosby, 2003.

Koch, A.L. Bacterial Growth and Form Dordrecht: Kluwer Academic Publishers, 2001.

The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck, 2006.

Richman, D.D., and R.J. Whitley. Clinical Virology. 2nd ed. Washington: American Society for Microbiology, 2002.

Shmaefsky, Brian. Meningitis. Philadelphia, PA: Chelsea House Publishers, 2005.

Tunkel, Allan R. Bacterial Meningitis. Philadelphia: Lippincott Williams & Wilkins, 2001.

PERIODICALS

Epidemics Of Meningococcal Disease. African Meningitis Belt, 2001. Weekly Epidemiological Record/World Health Organization 76, no. 37 (2001): 282-288.

Tsukahara, Hirokazu. Oxidant And Antioxidant Activities In Childhood Meningitis. Life Sciences 71, no. 23 (2002): 2797.

Rosalyn Carson-DeWitt

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Meningitis

Meningitis

Definition

Meningitis is an infection of the meninges and cerebral spinal fluid (CSF) caused by viruses , bacteria, or fungi. The meninges are the membranes that cover the brain and spinal cord. CSF is clear liquid that surrounds and helps protect the brain and spinal cord.

Description

Meningitis can be caused by the spread of viruses, bacteria, or fungi into the cerebral spinal fluid. These pathogens can invade the CSF directly, but are more likely reach the meninges by traveling through the bloodstream from an infection in another part of the body. Infections of the ear or sinuses are particularly likely to result in meningitis. The severity of the disease varies from mild to fatal depending on the cause.

Viral meningitis is the most common form of the disease, and it is also the mildest. Except for newborns, most people who develop viral meningitis recover completely within 7–10 days. In newborns, viral meningitis can be fatal. In the United States, about 10,000 cases of viral meningitis are reported each year, although some experts believe that the actual rate is ten times higher. Because many people recover from mild viral meningitis without treatment, many cases go unreported.

Bacterial meningitis is uncommon, but it is the most dangerous form of the disease. Left untreated, it is always fatal. Even when successfully treated it can cause permanent damage to the nervous system that can result in hearing loss , vision loss, and on-going seizures. The incidence of bacterial meningitis has dropped dramatically in the developed world since the 1990s because of routine immunization against the three most common types of bacteria that cause meningitis. In parts of the world where access to medical care is limited, bacterial meningitis is common and remains a significant cause of death , especially young children.

Fungal meningitis is uncommon. It occurs most often in people with compromised immune systems, especially individuals with AIDS . Drug allergies , certain autoimmune diseases, and some types of cancer can also cause inflammation of the meninges or noninfectious meningitis.

Demographics

Although anyone can develop meningitis, it is most likely to occur among newborns and children under age 5 who have not been vaccinated and adolescents ages 15–24. The very old are also at higher risk for contracting the disease. People who live group settings such as nursing homes, assisted living facilities , dormitories, military bases, or prisons are more likely to contract the disease. Meningitis is contagious and spreads easily through people living in close contact. Individuals who work with domestic animals, such as cattle and sheep, are at higher risk for contracting meningitis caused by listeria bacteria, although most people exposed to this bacterium, which is found in soil, dust, and on animals, do not become sick. People with diseases that weaken the immune system , such as diabetes or AIDS, those taking drugs that suppress immune system functioning, and people who have had their spleen (a part of the immune system) removed are also at higher risk.

Causes and symptoms

About 90% of cases of viral meningitis is caused by viruses from the enterovirus family. Viruses from this family also cause viral gastritis (stomach flu). However, viruses that cause mumps, measles, and polio can also cause viral meningitis. Although these diseases are uncommon in developed countries, they are still prevalent in the developing world and may be of concern to travelers.

Bacterial meningitis is caused primarily by four types of bacteria.

  • Streptococcus pneumoniae. This is also called pneumococcal meningitis. The bacterium also causes pneumonia, ear, and sinus infections. It is a leading cause of bacterial meningitis in young children.
  • Neisseria meningitidis. Also called meningococcal meningitis, this bacterium is highly contagious and is often responsible for outbreaks of meningitis among young adults.
  • Haemophilus influenzae. Routine childhood vaccinations against Haemophilus bacteria have been available since the 1990s and in the developed world have substantially reduced this cause of meningitis.
  • Listeria monocytogenes. Pregnant women and older adults are at higher risk than other groups for contracting listeria meningitis. Listeria can cross the placenta and kill a developing fetus.

Symptoms for all types of meningitis usually develop suddenly within one or two days, and are similar. Symptoms include an excruciating headache, stiff neck, substantial fever, nausea, vomiting, seizures, confusion, and lethargy. These symptoms often, but not always, follow another type of infection (e.g., respiratory, ear, sinus). Individual who develop these symptoms need immediate medical care. It is not possible to tell the cause of the meningitis from symptoms alone. Untreated bacterial meningitis can cause death within two days, so it is necessary to treat all suspected meningitis as if it has a bacterial cause until proven differently.

Diagnosis

Bacterial meningitis is definitively diagnosed by finding bacteria in the CSF. A sample of CSF is obtained by a lumbar puncture (spinal tap), examined under the microscope, and cultured to determine the type of bacteria present. The results can take up to one week. In 2007, the United States Food and Drug Administration (FDA) approved a rapid test for viral meningitis called the Xpert EV test. Using a sample of CSF, this test can accurately identify about 90% of viral meningitis cases in less than three hours. Since bacterial meningitis is often fatal, if no virus is found in the CSF, the disease is treated as if it is caused by bacteria until proven otherwise.

Treatment

There is no cure for viral meningitis. Symptoms such as pain , fever, and dehydration are treated. Young children may need to be hospitalized. With supportive care, most people recover within two weeks with no lasting complications.

Bacterial meningitis is treated immediately in a hospital with intravenous (IV) antibiotics . The specific antibiotic depends on the type of bacterium causing the infection. Until that determination is made, a broad-spectrum antibiotic that kills the most common types of bacteria is administered. People with bacterial meningitis may need additional treatment for shock, seizures, dehydration, and brain swelling. Serious cases of bacterial meningitis may require treatment in an intensive care unit (ICU) and life support.

Prognosis

With the exception of newborns and people with severely suppressed immune systems, few people die from viral meningitis and fewer than 1% have any complications from the disease.

Untreated bacterial meningitis is fatal. When treated with antibiotics, about 75% of patients recover, although the exact rate varies depending on the specific bacterium causing the infection. Pneumococcal meningitis has the highest death rate. Lasting complications from bacterial meningitis occur among about one-quarter of those who recover.

Prevention

Viral meningitis cannot be prevented. Its spread can be reduced by good hygiene practices such as frequent hand washing and not sharing personal items. Immunization is the best defense against bacterial meningitis. Vaccines are available that protect against Haemophilus influenzae. type b (Hib vaccine), pneumococcal meningitis (PCV7 vaccine for young children, PPV vaccine for older children and adults), and meningococcal meningitis (MCV4).

QUESTIONS TO ASK YOUR DOCTOR

  • Do I need to be hospitalized?
  • If I have viral meningitis how long will it take for me to get back to my normal daily activities?
  • What sort of complications should I look for if I have bacterial meningitis? Can they be prevented?
  • Are there immunizations I can have to help prevent bacterial meningitis?
  • Can other people catch this disease from me?

Caregiver concerns

Caregivers of the elderly, especially those living in group situations such as nursing homes, should encourage their charges ask their healthcare provider whether vaccines against meningitis are appropriate for them.

Resources

BOOKS

Beers, Mark H., Robert S. Porter, and Thomas V. Jones, eds. “Acute Bacterial Meningitis.” In The Merck Manual, 18th ed. Whitehouse Station, NJ: Merck, 2007. http://www.merck.com/mmhe/sec06/ch089/ch089b.html.

Goldman, Lee and Dennis Ausiello., eds. Cecil Textbook of Medicine., 23rd ed. Philadelphia Saunders Elsevier, 2008.

Goldsmith, Connie Meningitis, new ed. Minneapolis, MN: Twenty-First Century Books, 2008.

Harrison's Principles of Internal Medicine, 17th ed. New York, NY: McGraw-Hill, 2008.

ICON Health Publications. Bacterial Meningitis: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References. San Diego, CA: ICON Health Publications, 2004.

Marcovitz, Hal. Meningitis. San Diego., CA: ReferencePoint Press, 2008.

PERIODICALS

Torpy, Janet M. “Meningitis.” Journal of the American Medical Association. 297 no. 1 (January 3, 2007.): 122. http://jama.ama-assn.org/cgi/reprint/297/1/122.pdf.

OTHER

“Meningitis.” Mayo Clinic.com. February 5, 2008 [cited April 2, 2008]. http://www.mayoclinic.com/health/meningitis/DS00118.

“Meningitis.” MedlinePlus. April 2, 2008 [cited April 3, 2008]. http://www.nlm.nih.gov/medlineplus/meningitis.html.

Razonable, Robert. “Meningitis.” eMedicine.com. November 26,2007 [cited April 2, 2008]. http://www.emedicine.com/med/TOPIC2613.HTM.

Vokshoor, Amir. “Viral Meningitis”. August 23, 2007 [cited April 2, 2008]. http://www.emedicine.com/neuro/TOPIC607.HTM.

ORGANIZATIONS

Meningitis Research Foundation, Midland Way, Thornbury, Bristol,, BS35 2B5, 01454 281811, 01454 281094, http://www.meningitis.org.

National Institute of Allergy and Infectious Diseases Office of Communications and Government Relations, 6610 Rockledge Drive, MSC 6612, Bethesda, MD, 20892-6612, (301) 496-5717, (866) 284-4107 or TDD: (800) 877-8339 (for hearing impaired), (301) 402-3573, http://www3.niaid.nih.gov.

United States Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA, 30333, (404) 639-3534, (800) 311-3435, [email protected], http://www.cdc.gov.

Helen Davidson

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Meningitis

Meningitis

Meningitis is a potentially fatal inflammation of the meninges, the thin, membranous covering of the brain and the spinal cord. Meningitis is most commonly caused by infection (by bacteria , viruses, or fungi ), although it can also be caused by bleeding into the meninges, cancer , or diseases of the immune system .


Anatomical considerations

The meninges are three separate membranes, layered together, which serve to encase the brain and spinal cord. The dura is the toughest, outermost layer, and is closely attached to the inside of the skull. The middle layer, the arachnoid, is important in the normal flow of the cerebrospinal fluid (CSF), a lubricating fluid which bathes both the brain and the spinal cord. The innermost layer, the pia, helps direct brain blood vessels into the brain. The space between the arachnoid and the pia contains CSF, which serves to help insulate the brain from trauma. Through this space course many blood vessels.

CSF, produced within specialized chambers deep inside the brain, flows over the surface of the brain and spinal cord. This fluid serves to cushion these relatively delicate structures, as well as supplying important nutrients for brain cells. CSF is reabsorbed by blood vessels which are located within the meninges.

Because the brain is enclosed in the hard, bony case of the skull, any disease process which produces swelling will ultimately prove destructive to the brain. The skull cannot expand at all, so when swollen brain tissue pushes up against the skull's hard bone, the brain tissue becomes damaged and may ultimately die. Furthermore, swelling on the right side of the brain will not only cause pressure and damage to that side of the brain, but by taking up precious space within the tight confines of the skull, the left side of the brain will also be pushed up against the hard surface of the skull, causing reciprocal damage to that side of the brain as well.

The cells of the brain require a very well-regulated environment for optimal function. Careful balance ofoxygen , carbon dioxide , glucose (sugar), sodium , calcium , potassium, and other substances must be maintained in order to avoid damage to the relatively unforgiving brain tissue.

The cells lining the brain's capillaries (tiny blood vessels) are specifically designed to prevent many substances from passing into brain tissue. This is commonly referred to as the blood-brain barrier. The blood-brain barrier prevents various toxins (substances which could be poisonous to brain tissue), as well as many agents of infection, from crossing from the blood stream into the brain tissue. While this barrier obviously is an important protective feature for the brain, it also serves to complicate therapy in the case of an infection, by making it difficult for medications to pass out of the blood and into the brain tissue where the infection resides.


Infectious causes of meningitis

The most common infectious causes of meningitis vary according to an individual host's age, habits and living environment, and health status. In newborns, the most common agents of meningitis are those which are contracted from the newborn's mother, including Group B streptococci (becoming an increasingly common infecting organism in the newborn period),Escherichia coli , and Listeria monocytogenes. Older children are more frequently infected by Haemophilus influenzae, Neisseria meningitidis, and Streptococcus pneumoniae, while adults are infected by S. pneumoniae and N. meningitidis. N. meningitidis is the only organism that can cause epidemics of meningitis. These have occurred in particular when a child in a crowded day-care situation or a military recruit in a crowded training camp has fallen ill with N. meningitidis meningitis.

Viral causes of meningitis include the herpes simplex viruses, mumps and measles viruses (against which most children are protected due to mass immunization programs), the virus which causes chicken pox, the rabies virus, and a number of viruses which are acquired through the bite of infected mosquitoes . Patients with AIDS (acquired immune deficiency syndrome ) are more susceptible to certain infectious causes of meningitis, including by certain fungal agents, as well as by the agent which causes tuberculosis . Patients who have had their spleens removed, or whose spleens are no longer functional (as in the case of patients with sickle cell disease) are more susceptible to certain infections, including those caused by N. meningitidis and S. pneumoniae.


How the infectious agents of meningitis gain access to the meninges

The majority of meningitis infections are acquired by blood-borne spread. An individual may have another type of infection (of the lungs, throat, or tissues of the heart ) caused by an organism which can also cause meningitis. The organism multiplies, finds its way into the blood stream, and is delivered in sufficient quantities to invade past the blood-brain barrier.

Direct spread occurs when an already resident infectious agent spreads from infected tissue next to or very near the meninges, for example from an ear or sinus infection. Patients who suffer from skull fractures provide openings to the sinuses, nasal passages, and middle ears. Organisms which frequently live in the human respiratory system can then pass through these openings to reach the meninges and cause infection. Similarly, patients who undergo surgical procedures or who have had foreign bodies surgically placed within their skulls (such as tubes to drain abnormal amounts of accumulated CSF) have an increased risk of the organisms causing meningitis being introduced to the meninges.

The least common method by which the organisms causing meningitis are transmitted, but one of the most interesting, is called intraneural spread. This involves an organism spreading along a nerve, and using that nerve as a kind of ladder into the skull where the organism can multiply and cause meningitis. Herpes simplex virus is known to use this type of spread, as is the rabies virus.


Symptoms of meningitis

The most classic symptoms of meningitis (particularly of bacterial meningitis) include fever, headache, vomiting, photophobia (sensitivity to light ), irritability, lethargy (severe fatigue), and stiff neck. The disease progresses with seizures, confusion, and eventually coma .

A very young infant may not show the classic signs of meningitis. Early in infancy, a baby's immune system is not yet developed enough to mount a fever in response to infection, so fever may be absent. Some infants with meningitis have seizures as their only identifiable symptom.


How meningitis damages the brain

Damage due to meningitis occurs from a variety of phenomena. The action of infectious agents on the brain tissue is one direct cause of damage. Other types of damage may be due to mechanical effects of swelling of brain tissue, and compression against the bony surface of the skull. Swelling of the meninges may interfere with the normal absorption of CSF by blood vessels, causing accumulation of CSF and damage due to resulting pressure on the brain. Interference with the brain's carefully regulated chemical environment may cause damaging amounts of normally present substances (carbon dioxide, potassium) to accumulate. Inflammation may cause the blood-brain barrier to become less effective at preventing the passage of toxic substances into brain tissue.


Long term complications of meningitis

The most frequent long term effects of meningitis include deafness and blindness, due to compression of specific nerves and brain areas responsible for the senses of hearing and sight. Some patients develop permanent seizure disorders, requiring life-time treatment with anti-seizure medications. Scarring of the meninges may result in obstruction of the normal flow of CSF, causing abnormal accumulation of CSF. This may be a chronic problem for some patients, requiring the installation of tubes to regularly drain the accumulation.


Diagnosis

A number of techniques are used when examining a patient suspected of having meningitis to verify the diagnosis . Certain manipulations of the head (lowering the head, chin towards chest, for example) are difficult to perform and painful for a patient with meningitis.

The most important test used to diagnosis meningitis is the lumbar puncture (commonly called a spinal tap). Lumbar puncture (LP) involves the insertion of a thin needle into a space between the vertebrae in the lower back, and the withdrawal of a small amount of CSF. The CSF is then examined under a microscope . Normal CSF contains set percentages of glucose and protein. These percentages will vary with bacterial, viral, or other causes of meningitis. For example, bacterial meningitis causes a greatly lower than normal percentage of glucose to be present in CSF, as the bacteria are essentially "eating" the host's glucose, and using it for their own nutrition and energy production. Normal CSF should contain no white blood cells (infection fighting cells), so the presence of white blood cells in CSF is another indication of meningitis. Some of the withdrawn CSF is also put into special lab dishes to allow growth of the infecting organism, which can then be identified more easily.

In a few rare instances, lumbar puncture cannot be performed, because the amount of swelling within the skull is so great that the intracranial pressure (pressure within the skull) is extremely high. This pressure is always measured immediately upon insertion of the LP needle. If it is found to be very high, no fluid is withdrawn, because withdrawal of fluid could cause herniation of the brain stem. Herniation of the brain stem occurs when the part of the brain connecting to the spinal cord is thrust through the opening at the base of the skull into the spinal canal. Such herniation will cause compression of those structures within the brain stem that control the most vital functions of the body (breathing, heart beat, consciousness). Death or permanent debilitation follows herniation of the brain stem.


Treatment

Antibiotic medications (forms of penicillins and cephalosporins, for example) are the most important element of treatment against bacterial agents of meningitis. Because of the effectiveness of the blood-brain barrier in preventing passage of substances into the brain, medications must be delivered directly into the patient's veins (intravenous or IV) at very high doses. Antiviral medications (acyclovir) may be helpful in the case of viral meningitis, and antifungal medications are available as well.

Other treatment for meningitis involves decreasing inflammation (with steroid preparations) and paying careful attention to the balance of fluids, glucose, sodium, potassium, oxygen, and carbon dioxide in the patient's system. Patients who develop seizures will require medications to halt the seizures and prevent their return.


Prevention

A series of vaccines against Haemophilus influenzae, started at two months of age, has greatly reduced the incidence of that form of meningitis. Vaccines also exist against Neisseria meningitidis and Streptococcus pneumoniae bacteria, but these vaccines are only recommended for those people who have particular susceptibility to those organisms, due to certain immune deficiencies, lack of a spleen, or sickle cell anemia .

Because N. meningitidis is known to cause epidemics of disease, close contacts of patients with such meningitis (other children in day care with the patient, other military personnel within the same training camp, and people living within the patient's household), are treated with Rifampin. This generally prevents spread of the disease.

Mothers with certain risk factors may be treated with antibiotics during labor, to prevent the passage of certain organisms which may cause meningitis in the newborn (particularly Group B streptococcus).


Resources

books

Andreoli, Thomas E., et al. Cecil Essentials of Medicine. Philadelphia: W. B. Saunders Company, 1993.

Berkow, Robert, and Andrew J. Fletcher. The Merck Manual of Diagnosis and Therapy. Rahway, NJ: Merck Research Laboratories, 1992.

Cormican, M.G. and M.A. Pfaller. "Molecular Pathology of Infectious Diseases," in Clinical Diagnosis and Managementby Laboratory Methods. 20th ed. Philadelphia: W. B. Saunders, 2001.

Isselbacher, Kurt J., et al. Harrison's Principles of Internal Medicine. New York: McGraw Hill, 1994.

Kobayashi, G., Patrick R. Murray, Ken Rosenthal, and Michael Pfaller. Medical Microbiology. St. Louis, MO: Mosby, 2003.

Koch, A.L. Bacterial Growth and Form Dordrecht: Kluwer Academic Publishers, 2001.

Krugman, Saul, et al. Infectious Diseases of Children. St. Louis: Mosby-Year Book, Inc., 1992.

Richman, D.D., and R.J. Whitley. Clinical Virology. 2nd ed. Washington: American Society for Microbiology, 2002.

Tunkel, Allan R. Bacterial Meningitis. Philadelphia: Lippincott Williams & Wilkins, 2001.

Willett, Edward. Meningitis (Diseases and People). Berkeley Heights, NJ: Enslow Publsihers, 1999.

periodicals

"Pidemics Of Meningococcal Disease. African Meningitis Belt, 2001." Weekly Epidemiological Record/World Health Organization 76, no. 37 (2001): 282-288.

Tsukahara, Hirokazu. "Xidant And Antioxidant Activities In Childhood Meningitis." Life Sciences 71, no. 23 (2002): 2797.


Rosalyn Carson-DeWitt

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blood-brain barrier

—A blockade of cells separating the circulating blood from elements of the central nervous system (CNS); it acts as a filter, preventing many substances from entering the central nervous system.

Cerebrospinal fluid (also called CSF)

—Fluid made in chambers within the brain; this fluid then flows over the surface of the brain and spinal cord, providing nutrition to cells of the nervous system, as well as cushioning.

Lumbar puncture (also called LP)

—A medical test in which a very narrow needle is inserted into a specific space between the vertebrae of the lower back in order to draw off and examine a sample of CSF.

Meninges

—The three layer membranous covering of the brain and spinal cord, composed of the dura, arachnoid, and pia. Provides protection for the brain, as well as housing many blood vessels.

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