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Coma

Coma

Definition

Coma, from the Greek word "koma," meaning deep sleep, is a state of extreme unresponsiveness, in which an individual exhibits no voluntary movement or behavior. Furthermore, in a deep coma, even painful stimuli (actions which, when performed on a healthy individual, result in reactions) are unable to affect any response, and normal reflexes may be lost.

Description

Coma lies on a spectrum with other alterations in consciousness. The level of consciousness required by, for example, someone reading this passage lies at one extreme end of the spectrum, while complete brain death lies at the other end of the spectrum. In between are such states as obtundation, drowsiness, and stupor. All of these are conditions which, unlike coma, still allow the individual to respond to stimuli, although such a response may be brief and require stimulus of greater than normal intensity.

In order to understand the loss of function suffered by a comatose individual, it is necessary to first understand the important characteristics of the conscious state. Consciousness is defined by two fundamental elements: awareness and arousal.

Awareness allows one to receive and process all the information communicated by the five senses, and thus relate to oneself and to the outside world. Awareness has both psychological and physiological components. The psychological component is governed by an individual's mind and mental processes. The physiological component refers to the functioning of an individual's brain, and therefore that brain's physical and chemical condition. Awareness is regulated by cortical areas within the cerebral hemispheres, the outermost layer of the brain that separates humans from other animals by allowing for greater intellectual functioning.

Arousal is regulated solely by physiological functioning and consists of more primitive responsiveness to the world, as demonstrated by predictable reflex (involuntary) responses to stimuli. Arousal is maintained by the reticular activating system (RAS). This is not an anatomical area of the brain, but rather a network of structures (including the brainstem, the medulla, and the thalamus) and nerve pathways, which function together to produce and maintain arousal.

Causes and symptoms

Coma, then, is the result of something that interferes with the functioning of the cerebral cortex and/or the functioning of the structures which make up the RAS. In fact, a huge and varied number of conditions can result in coma. A good way of categorizing these conditions is to consider the anatomic and the metabolic causes of coma. Anatomic causes of coma are those conditions that disrupt the normal physical architecture of the brain structures responsible for consciousness, either at the level of the cerebal cortex or the brainstem, while metabolic causes of coma consist of those conditions that change the chemical environment of the brain, thereby adversely affecting function.

There are many metabolic causes of coma, including:

  • A decrease in the delivery to the brain of substances necessary for appropriate brain functioning, such as oxygen, glucose (sugar), and sodium.
  • The presence of certain substances that disrupt the functioning of neurons. Drugs or alcohol in toxic quantities can result in neuronal dysfunction, as can substances normally found in the body, but that, due to some diseased state, accumulate at toxic levels. Accumulated substances that might cause coma include ammonia due to liver disease, ketones due to uncontrolled diabetes, or carbon dioxide due to a severe asthma attack.
  • The changes in chemical levels in the brain due to the electrical derangements caused by seizures.

Diagnosis

As in any neurologic condition, history and examination form the cornerstone of diagnosis when the patient is in a coma; however, history must be obtained from family, friends, or EMS. The Glasgow Coma Scale is a system of examining a comatose patient. It is helpful for evaluating the depth of the coma, tracking the patient's progress, and predicting (somewhat) the ultimate outcome of the coma. The Glasgow Coma Scale assigns a different number of points for exam results in three different categories: opening the eyes, verbal response (using words or voice to respond), and motor response (moving a part of the body). Fifteen is the largest possible number of total points, indicating the highest level of functioning. The highest level of functioning would be demonstrated by an individual who spontaneously opens his/her eyes, gives appropriate answers to questions about his/her situation, and can carry out a command (such as "move your leg" or "nod your head"). Three is the least possible number of total points and would be given to a patient for whom not even a painful stimulus is sufficient to provoke a response. In the middle are those patients who may be able to respond, but who require an intense or painful stimulus, and whose response may demonstrate some degree of brain malfunctioning (such as a person whose only response to pain in a limb is to bend that limb in toward the body). When performed as part of the admission examination, a Glasgow score of three to five points often suggests that the patient has likely suffered fatal brain damage, while eight or more points indicates that the patient's chances for recovery are good. Expansion of the pupils and respiratory pattern are also important. Metabolic causes of coma are diagnosed from blood work and urinalysis to evaluate blood chemistry, drug screen, and blood cell abnormalities that may indicate infection. Anatomic causes of coma are diagnosed from CT (computed tomography ) or MRI (magnetic resonance imaging ) scans.

Treatment

Coma is a medical emergency, and attention must first be directed to maintaining the patient's respiration and circulation, using intubation aand ventilation, administration of intravenous fluids or blood as needed, and other supportive care. If head trama has not been excluded, the neck should be stablized in the event of fracture. It is obviously extremely important for a physician to determine quickly the cause of a coma, so that potentially reversible conditions are treated immediately. For example, an infection may be treated with antibiotics ; a brain tumor may be removed; and brain swelling from an injury can be reduced with certain medications. Various metabolic disorders can be addressed by supplying the individual with the correct amount of oxygen, glucose, or sodium; by treating the underlying disease in liver disease, asthma, or diabetes; and by halting seizures with medication. Because of their low incidence of side effects and potential for prompt reversal of coma in certain conditions, glucose, the B-vitamin thiamine, and Narcan (to counteract any narcotic-type drugs) are routinely given.

Prognosis

Some conditions that cause coma can be completely reversed, restoring the individual to his or her original level of functioning. However, if areas of the brain have been sufficiently damaged due to the severity or duration of the condition which led to the coma, the individual may recover from the coma with permanent disabilities, or may even never regain consciousness. Take, for example, the situation of someone whose coma was caused by brain injury in a car accident. Such an injury can result in one of three outcomes. In the event of a less severe brain injury, with minimal swelling, an individual may indeed recover consciousness and regain all of his or her original abilities. In the event of a more severe brain injury, with swelling that resulted in further pressure on areas of the brain, an individual may regain consciousness, but may have some degree of impairment. The impairment may be physical (such as paralysis of a leg) or may even result in a change in the individual's intellectual functioning and/or personality. The most severe types of brain injury, short of death, result in states in which the individual loses all ability to function and remains deeply unresponsive. An individual who has suffered such a severe brain injury may remain in a coma indefinitely. This condition is termed persistent vegetative state.

Outcome from a coma is therefore quite variable and depends a great deal on the cause and duration of the coma. In the case of drug poisonings, extremely high rates of recovery can be expected following prompt medical attention. Patients who have suffered head injuries tend to do better than do patients whose coma was caused by other types of medical illnesses. Leaving out those people whose coma followed drug poisoning, only about 15% of patients who remain in a coma for more than just a few hours make a good recovery. Those adult patients who remain in a coma for greater than four weeks have almost no chance of eventually regaining their previous level of functioning. On the other hand, children and young adults have regained functioning even after two months in a coma.

Resources

ORGANIZATIONS

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

Coma Recovery Association, Inc. 570 Elmont Rd., Suite 104, Elmont, NY 11003. (516) 355-0951.

KEY TERMS

Anatomic Related to the physical structure of an organ or organism.

Metabolic Refers to the chemical processes of an organ or organism.

Neuron The cells within the body which make up the nervous system, specifically those along which information travels.

Physiological Pertaining to the functioning of an organ, as governed by the interactions between its physical and chemical conditions.

Psychological Pertaining to the mind, its mental processes, and its emotional makeup.

Stimulus/stimuli Action or actions performed on an individual which predictably provoke(s) a reaction.

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coma

coma All persons in coma are unconscious, but not all who are unconscious are in coma. Sleep is a state of unconsciousness from which a person can be roused. The vegetative state is unconsciousness with the eyes open, the person being awake but not aware. Coma is a state of unrousable, sleep-like (eyes closed) unconsciousness. Although asleep and unaware, only those in the deepest states of coma are unresponsive. Most patients in coma respond reflexly — the pupils react to light and the limbs move in response to a painful stimulus (such as pinching the skin or pressing the nailbed). A person in coma may move restlessly and make sounds, but utters no words.

Different levels of coma, and of impaired consciousness not severe enough to be called coma, are defined by the Glasgow Coma Scale or Score — often referred to internationally as the GCS. This grades three items of behaviour: eye opening, motor responses (limb movements on command or in response to a painful stimulus), and verbal activity. For each of these there is a score of 1 to 5 according to how good the response is, with higher numbers indicating the more normal responses. At a combined score of 15 the eyes open spontaneously, commands are obeyed, and the patient can say who he is and where he is and when it is. A patient is considered to be in coma if the eyes remain closed, there are no motor responses on command, and no recognizable words are uttered — if all three of these conditions are satisfied, as well as the total score being 8 or less. At the lowest score of 3 the eyes are closed, the limbs show no response even to pain, and no sounds at all are made.

Coma is associated with loss of function in the arousal centre in the brain stem which is responsible both for eye opening and for activating the cerebral cortex, which has to be functioning for a person to be aware of self and surroundings. Some causes of coma temporarily affect the arousal mechanisms alone. These include normal doses of anaesthetic agents, overdoses of sedative drugs or alcohol, and a generalized epileptic seizure. Toxic body chemicals can also cause coma, due to disease in other organs, as a complication of diabetes, or of failure of kidney or liver function. More often coma is a feature of major structural insults in various parts of the brain, such as those resulting from severe head injury, brain haemorrhage, infection, tumour, or oxygen lack (either in part of the brain from a blocked blood vessel (stroke), or in the brain as a whole due to stoppage of the heart or the breathing). In all these conditions the development of coma is a sign that the condition is very serious and that there is much less likelihood of recovery than if coma had not occurred.

The person in coma is at immediate risk of obstruction of the airway, as the normal coughing reflex is depressed. Obstruction may come from the tongue falling back or from inhalation of vomited stomach contents. This complication, which can be fatal, is less likely to occur if as a first-aid measure the person is turned over with the face down — the so-called coma position. Paramedics or doctors will later deal more effectively with this threat by passing a tube through the nose or mouth into the trachea (endotracheal intubation), and artificial ventilation may be set up. Since a person in coma is unable to take food and fluids normally, if coma lasts more than 24 hours artificial feeding will be necessary to ensure survival. This may be by a tube in the stomach (passed through the mouth or nose), or by a infusion into a vein.

Recovery from coma depends on the cause. Chemically-caused coma with no other brain damage or complications can be followed by complete recovery. When there has been a major structural insult the rapidity of recovery and the degree of residual disability will depend on how much permanent brain damage has been caused. How long the coma lasts is often a good indication of how severe this damage is, but a good recovery is still possible when coma has lasted 2 or 3 weeks. On the other hand, severe brain damage can occur without the patient ever being in coma, for example after a severe stroke. In survivors of even the most severe brain damage, however, coma seldom lasts more than 3–4 weeks; the eyes then open and the patient passes into another state of reduced responsiveness such as the vegetative state. Press reports of patients in ‘coma’ for months or years are therefore misleading.

Bryan Jennett

Bibliography

Teasdale, G. and and Jennett, B. (1976). Assessment of coma and impaired consciousness. A practical scale. Lancet, 1, 1031.


See also brain death; consciousness; vegetative state.

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Coma

Coma

An abnormal state of profound unconsciousness accompanied by the absence of all voluntary behavior and most reflexes.

A coma may be induced by a severe neurological injuryeither temporary or permanentor by other physical trauma. A comatose individual cannot be aroused by even the most intense stimuli, although he or she may show some automatic movements in response to pain . Comas often occur just before death in the course of many diseases. The affected brain cells may be either near the surface (cerebral cortex) or deeper in the brain (diencephalon or brainstem). Specific conditions that produce comas include cerebral hemorrhage; blood clots in the brain; failure of oxygen supply to the brain; tumors; intracranial infections that cause meningitis or encephalitis; poisoning, especially by carbon monoxide or sedatives; concussion; and disorders involving electrolytes. Comas may also be caused by metabolic abnormalities that impair the functioning of the brain through a sharp drop in the blood sugar level, such as diabetes.

The passage from wakefulness to coma can be rapid and/or gradual. Often, it is preceded by lethargy and then a state resembling light sleep . In general, treatment of a coma involves avoiding further damage to the brain by maintaining the patient's respiratory and cardiac functions, and by an intravenous (usually glucose) nutritional supply to the brain.

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coma (in medicine)

coma, in medicine, deep state of unconsciousness from which a person cannot be aroused even by painful stimuli. The patient cannot speak and does not respond to command. Coma is the result of damage to the brain stem and cerebrum that may be caused by severe head or brain injury, cardiac arrest, stroke, diabetes, drug overdose, shock, or hemorrhage. It occurs just before death in many diseases. There are various depths of coma; the nature of the injury determines the level of supportive treatment necessary (see artificial life support). Survival and prognosis depend upon the cause, extent of damage, and duration of the coma.

The term persistent vegetative state was coined in 1972 to describe an unconscious state in which sleep and wake cycles remain and eyes may open, but there is no thinking, feeling, or awareness of one's surroundings (although one may react reflexive to certain stimulations). The brain stem is usually relatively intact but the cerebral cortex is severely impaired. It is this state that sometimes results from resuscitation and life support of people who otherwise would have died; partial emergence from such a state sometimes occurs with a year or two, but not after that.

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coma

co·ma1 / ˈkōmə/ • n. a state of deep unconsciousness that lasts for a prolonged or indefinite period, caused esp. by severe injury or illness. co·ma2 • n. (pl. co·mae / ˈkōmē/ ) Astron. a diffuse cloud of gas and dust surrounding the nucleus of a comet. ∎  Optics aberration that causes the image of an off-axis point to be flared like a comet.

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coma

coma 1 unnatural deep and prolonged sleep. XVII. — medical L. — Gr. kôma, kōmat-, rel. to koítē bed. keîsthai lie down.
Hence comatose XVIII.

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coma

coma The diffuse shell of gas, typically about 150 000km in diameter, which surrounds the nucleus of a comet. The coma and the nucleus form the ‘head’ of the comet.

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coma

coma 2 (bot.) tuft XVII; (astron.) nebulous envelope of a comet XVIII. — L. coma — Gr. kómē hair of the head; cf. COMET.

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COMA

COMA Committee on Medical Aspects of Food Policy; formerly a permanent Advisory Committee to the UK Department of Health.

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coma

coma State of unconsciousness brought about by head injury, brain disease, drugs, or lack of blood supply to the brain.

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coma

coma (koh-mă) n. a state of unrousable unconsciousness.

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coma (in astronomy)

coma, in astronomy: see comet.

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COMA

COMA (or Coma) (ˈkəʊmə) Committee on Medical Aspects of Food Policy

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coma

comadormer, former, korma, Norma, performer, pro-forma, stormer, transformer, trauma, warmer •sixth-former • barnstormer •aroma, carcinoma, chroma, coma, comber, diploma, glaucoma, Homer, lymphoma, melanoma, misnomer, Oklahoma, Omagh, roamer, Roma, romer, sarcoma, soma •beachcomber •bloomer, boomer, consumer, Duma, humour (US humor), Nkrumah, perfumer, puma, roomer, rumour (US rumor), satsuma, stumer, Sumer, tumour (US tumor) •zeugma • fulmar •bummer, comer, drummer, hummer, midsummer, mummer, plumber, rummer, strummer, summa, summer •latecomer • newcomer • agama •welcomer •astronomer, monomer •ashrama • isomer • gossamer •customer •affirmer, Burma, derma, Irma, murmur, squirmer, terra firma, wormer

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Coma

Coma ★★★ 1978 (PG)

A doctor discovers murder and corpsenabbing at her Boston hospital, defies her male bosses, and determines to find out what's going on before more patients die. Exciting, suspenseful fare, with Bujold impressive in lead. Based on the novel by Robin Cook. 113m/C VHS, DVD . Genevieve Bujold, Michael Douglas, Elizabeth Ashley, Rip Torn, Richard Widmark, Lois Chiles, Hari Rhodes, Tom Selleck, Ed Harris; D: Michael Crichton; W: Michael Crichton; C: Victor Kemper, Gerald Hirschfeld; M: Jerry Goldsmith.

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Coma

Coma

Definition

Coma, from the Greek word koma, meaning deep sleep, is a state of extreme unresponsiveness, in which an individual exhibits no voluntary movement or behavior. Furthermore, in a deep coma, even painful stimuli (actions which, when performed on a healthy individual, result in reactions) are unable to cause any response, and normal reflexes may be lost.

Description

The important characteristics of the conscious state is defined by two fundamental elements: awareness and arousal.

Awareness allows one to receive and process all the information communicated by the five senses. Awareness has both psychological and physiological components. The psychological component refers to an individual's mind and mental processes. The physiological component refers to the functioning of an individual's brain, and the physical and chemical condition of the brain. Awareness is regulated by cortical areas within the cerebral hemispheres, the outermost layer of the brain.

Arousal is regulated solely by physiological functioning and consists of more primitive responsiveness to the world, as demonstrated by predictable reflex (involuntary) responses to stimuli. Arousal is maintained by the reticular activating system (RAS), a network of brain structures, including the brainstem, the medulla, and the thalamus, and nerve pathways that function together to produce and maintain arousal.

Causes and symptoms

Coma is the result of something that interferes with the functioning of the cerebral cortex and/or the functioning of the structures that comprise the RAS. Several conditions can result in coma. Anatomic causes of coma are those conditions that disrupt the brain structures responsible for consciousness, either at the level of the cerebral cortex or the brainstem, while metabolic causes of coma consist of those conditions that change the chemical environment of the brain, thereby adversely affecting function.

There are many metabolic causes of coma, including:

  • a decrease in the delivery to the brain of substances necessary for appropriate brain functioning, such as oxygen, glucose (sugar), and sodium
  • the presence of certain substances such as drugs, alcohol, carbon dioxide, and ketones that disrupt the functioning of neurons
  • changes in chemical levels in the brain caused by seizures

Diagnosis

History and examination form the cornerstone of diagnosis when an individual is in a coma. However, history must be obtained from family, friends, or emergency medical service personnel.

The Glasgow Coma Scale is a system of examining a comatose person. It evaluates the depth of the coma, tracks the person's progress, and predicts the ultimate outcome of the coma. The Glasgow Coma Scale assigns a different number of points for exam results in three different categories: opening the eyes, verbal response, and motor response (moving a part of the body). Fifteen is the largest possible number of total points, indicating the highest level of functioning, which would be demonstrated by individuals who spontaneously open their eyes, give appropriate answers to questions about their situations, and can carry out a command such as moving a specific limb when ordered. Three is the least possible number of total points, and would be given to a person for whom not even a painful stimulus is sufficient to provoke a response. In the middle are those people who may be able to respond, but who require an intense or painful stimulus, and whose response may demonstrate some degree of brain malfunctioning. When performed as part of the admission examination, a Glasgow score of three to five points often suggests that an individual has likely suffered fatal brain damage, while eight or more points indicates that the person's chances for recovery are good.

Expansion of the pupils and respiratory pattern are also important. Metabolic causes of coma are diagnosed from blood work and urinalysis to evaluate blood chemistry, drug screen, and blood cell abnormalities that may indicate infection. Anatomic causes of coma are diagnosed from computed tomography (CT) or magnetic resonance imaging (MRI) scans.

Treatment

Coma is a medical emergency, and attention must first be directed to maintaining an individual's respiration and circulation, using intubation and ventilation, administration of intravenous fluids or blood as needed, and other supportive care. If head trauma has not been excluded, the neck should be stabilized in the event of fracture. It is extremely important for a physician to quickly determine the cause of a coma, so that potentially reversible conditions are immediately treated. These conditions may include an infection that can be treated with antibiotics, a brain tumor that can be removed, or brain swelling that can be reduced with certain medications.

Various metabolic disorders can be addressed by supplying an individual with the correct amount of oxygen, glucose, or sodium, by treating the underlying problem in liver disease, asthma, or diabetes, and by halting seizures with medication. Because of their low incidence of side effects and potential for prompt reversal of coma in certain conditions, glucose, the B-vitamin thiamine, and Narcan (to counteract any narcotic-type drugs) are routinely given.

Prognosis

Some conditions that cause coma can be completely reversed, restoring an individual to an original level of functioning. However, if areas of the brain have been sufficiently damaged due to the severity or duration of the condition that led to the coma, an individual may recover with permanent disabilities, either physical or mental, or may never regain consciousness. Short of death, the most severe types of brain injury result in states in which an individual loses all ability to function and remains deeply unresponsive. An individual who has suffered such a severe brain injury may remain in a coma indefinitely. This condition is termed a persistent vegetative state.

Outcome from a coma is therefore quite variable and depends a great deal on the cause and duration of the coma. In the case of drug poisonings, extremely high rates of recovery can be expected following prompt medical attention. Persons who have suffered head injuries tend to do better than do those whose coma was caused by medical illness. Besides those people whose coma results from drug poisoning, only about 15% of individuals who remain in a coma for more than just a few hours make a good recovery. Adult patients who remain in a coma for more than four weeks have almost no chance of eventually regaining their previous level of functioning. On the other hand, children and young adults have regained functioning after two months in a coma.

Health care team roles

Emergency medical team members are often first on the scene to provide a preliminary assessment of unconsciousness. In the hospital, a physician makes the diagnosis of coma, often with assistance from radiologists and laboratory technicians. Nurses provide supportive care throughout the duration of a coma. Physical therapists provide range of motion and other therapeutic movements designed to preserve normal muscular functioning.

Prevention

Medical conditions known to cause comas should be monitored and promptly treated. Applicable safety precautions and rules should be followed when engaging in any activity that has the potential for serious head injury.

KEY TERMS

Anatomic— Related to the physical structure of an organ or organism.

Metabolic— Refers to the chemical processes of an organ or organism.

Narcan— A drug that reverses the effects of narcotics.

Neuron— The cells within the body which comprise the nervous system.

Reticular activating system (RAS)— A network of structures, including the brainstem, medulla, and thalamus, and nerve pathways, which function together to produce and maintain arousal.

Stimulus— Action performed on an individual that predictably provokes a reaction.

Resources

BOOKS

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

Mindell, Amy, and Robert King. Coma, A Healing Journey: A Guide for Family Friends and Helpers. Portand, OR: Lao Tse Press, 1999.

O'Farrell, Maggie. After You'd Gone. New York: Viking Press, 2001.

Ropper, Allan H., and Joseph B. Martin. "Acute Confusional States and Coma." In Harrison's Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci et al. New York: McGraw-Hill, 1998, pp. 125-34.

Simon, Roger P. "Brain Death." In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, pp. 2027-8.

Simon, Roger P. "Coma and Disorders of Arousal." In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, pp. 2023-6.

Simon, Roger P. "Persistent Vegetative State." In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, pp. 2026-7.

PERIODICALS

Lodi, J. R. "When a Coma Isn't One." Time 157 no. 12 (March 26, 2001): 62.

Namen, A. M., et al. "Predictors of Successful Extubation in Neurosurgical Patients." American Journal of Respiratory and Critical Care Medicine 163 no. 3 Pt 1 (2001): 658-64.

Palmer, S., et al. "The Impact on Outcomes in a Community Hospital Setting of Using the AANS Traumatic Brain Injury Guidelines." Journal of Trauma 50 no. 4 (2001): 657-64.

Wallace, B.E., A. K. Wagner, E. P. Wagner, and J. T. McDeavitt. "A History and Review of Quantitative Electroencephalography in Traumatic Brain Injury." Journal of Head Trauma Rehabilitation 16 no. 2 (2001): 165-90.

Wilkins, I. A., D. K. Menon, and B. F. Matta. "Management of Comatose Head-Injured Patients: Are We Getting Any Better?" Anesthesia 56 no. 4 (2001): 350-69.

ORGANIZATIONS

American Academy of Neurology. 1080 Montreal Avenue, St. Paul, Minnesota 55116. (651) 695-1940. (651) 695-2791. 〈http://www.aan.com〉. [email protected]

Brain Injury Association. 105 North Alfred Street, Alexandria, VA 22314. (800) 444-6443. (703) 236-6000. (703) 236-6001. 〈http://www.biausa.org/Sportsfs.htm〉. [email protected]

International Brain Injury Association. 1150 South Washington Street, Suite 210, Alexandria, VA 22314. (703) 683-8400. (703) 683-8996. 〈http://www.internationalbrain.org〉. [email protected]

National Center for Injury Prevention and Control. Centers for Disease Control and Prevention, Mailstop F41, 4770 Buford Highway NE, Atlanta, GA 30341-3724. (770) 488-4031. (770) 488-4338. 〈http://www.cdc.gov/ncipc/dacrrdp/tbi.htm〉. [email protected]

OTHER

Coma Recovery Association. 〈http://www.comarecovery.org〉.

Glasgow Coma Score. 〈http://www.trauma.org/scores/gcs.html〉.

National Academy of Child Development. 〈http://www.nacd.org/articles/coma.html〉.

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

Neurology Channel. 〈http://www.neurologychannel.com/coma/〉.

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Coma

Coma

Consciousness

Causes of coma

Outcome

Glasgow coma scale

The ethical dilemma presented by persistent coma

Resources

Coma, from the Greek word koma, meaning deep sleep, is a state of extreme unresponsiveness in which an individual exhibits no voluntary movement or behavior. In a deep coma, stimuli, even painful stimuli, are unable to effect any response. Normal reflexes may be lost.

Coma lies on a spectrum with other alterations in consciousness. The level of consciousness that readers of this article are currently enjoying is at one end of the spectrum, while complete brain death is at the other end of the spectrum. In between are such states as obtundation, drowsiness, and stupor, which all allow the individual to respond to stimuli, though such response may be brief and require a stimulus of greater than normal intensity.

Consciousness

In order to understand the loss of function suffered by a comatose individual, consider the important characteristics of the conscious state. Consciousness is defined by two fundamental elements: awareness and arousal.

Awareness allows humans to receive and process information communicated by the five senses and thereby relate to themselves and the rest of the world.

Awareness has psychological and physiological components. The psychological component is governed by an individuals mind and its mental processes. The physiological component refers to the functioning the physical and chemical conditionof an individuals brain. Awareness is regulated by areas within the cerebral hemispheres, the outermost layer of the brain, which separates humans from other animals because it allows greater intellectual functioning.

Arousal is regulated solely by physiological functioning. Its primitive responsiveness to the world is demonstrated by predictable reflex (involuntary) responses to stimuli. Arousal is maintained by the reticular activating system (RAS). This is not an anatomical area of the brain but rather a network of structures (including the brain stem, the medulla, and the thalamus) and nerve pathways which function together to produce and maintain arousal.

Causes of coma

Coma is the result of something which interferes with the functioning of the cerebral cortex and/or the functioning of the structures that make up the RAS. The number of conditions that could result in coma is mind-boggling. A good way of categorizing these conditions is to consider the anatomic and the metabolic causes of coma. Anatomic causes of coma are those conditions that disrupt the normal physical architecture of the brain structures responsible for consciousness. Metabolic causes of coma consist of those conditions that change the chemical environment of the brain and thereby adversely affect function.

Anatomic causes of coma include brain tumors, infections, and head injuries. All three types of condition can affect the brains functioning by actually destroying brain tissue. They may also affect the brains functioning by taking up too much space within the skull. The skull is a very hard, bony structure that is unable to expand in size. If something within the skull begins to require more space (for example an expanding tumor or an injured/infected

area of the brain that is swelling) other areas of the brain are compressed against the hard surface of the skull, which results in damage to these areas.

There are many metabolic causes of coma, including the following: (1) A decrease in the delivery of substances necessary for appropriate brain functioning, such as oxygen, glucose, and sodium. (2) The presence of certain substances disrupting the functioning of neurons. Drugs or alcohol in toxic quantities can result in neuronal dysfunction, as can some substances normally found in the body, that accumulate at toxic levels due to some disease state. Accumulated substances that might cause coma include ammonia due to liver disease, ketones due to uncontrolled diabetes, or carbon dioxide due to a severe asthma attack. (3) The changes in chemical levels in the brain due to the electrical derangements caused by seizures.

Outcome

It is extremely important for a physician to quickly determine the cause of a coma, so that potentially reversible conditions are treated immediately. For example, an infection may be treated with antibiotics, a brain tumor may be removed, and brain swelling from an injury can be reduced with certain medications. Furthermore, various metabolic disorders can be addressed by supplying the individual with the correct amount of oxygen, glucose, or sodium, by treating the underlying disease in liver disease, asthma, or diabetes, and by halting seizures with medication.

Some conditions that cause coma can be completely reversed, restoring the individual to his or her original level of functioning. However, if areas of the brain have been sufficiently damaged because of the severity or duration of the condition that led to the coma, the individual may recover from the coma with permanent disabilities, or may never regain consciousness. Take the situation of someone whose coma was caused by brain injury in a car accident. Such an injury can result in one of three outcomes. In the event of a less severe brain injury, with minimal swelling, an individual may indeed recover consciousness and regain all of his or her original abilities. In the event of a more severe brain injury, with swelling that results in further pressure on areas of the brain, an individual may regain consciousness, but with some degree of impairment. The impairment may be physical, such as paralysis of a leg, or result in a change in the individuals intellectual functioning and/or personality. The most severe types of brain injury result in states in which the individual loses all ability to function and remains deeply unresponsive. An individual who has suffered such a brain injury may remain in a coma indefinitely.

Outcome from a coma depends on its cause and duration. In drug poisonings, extremely high rates of recovery can be expected, following prompt medical attention. Patients who have suffered head injuries tend to do better than patients whose coma was caused by other types of medical illnesses. Excluding drug-poisoning induced comas, only about 15% of patients who remain in a coma for more than a few hours make a good recovery. Adult patients who remain in a coma for more than four weeks have almost no chance of regaining their previous level of functioning. However, children and young adults have regained functioning after two months in a coma.

Glasgow coma scale

The Glasgow Coma Scale, a system of examining a comatose patient, can be helpful for evaluating the depth of the coma, tracking the patients progress, and possibly predicting ultimate outcome of the coma. The Glasgow Coma Scale assigns a different number of points for examination results in three different categories: opening the eyes, verbal response (using words or voice to respond), and motor response (moving a part of the body). Fifteen indicates the highest level of functioning. An individual who spontaneously opens his or her eyes, gives appropriate answers to questions about his or her situation, and can follow a command (such as move your leg, nod your head) has the highest level of functioning. Three is the smallest possible number of points, and would be given to a patient who is unresponsive to a painful stimulus. In the middle range are those patients who may be able to respond, but who require an intense or painful stimulus, and whose response may demonstrate some degree of brain malfunctioning. When performed as part of the admission examination, a Glasgow score of three to five points suggests that the patient likely has suffered fatal brain damage, while eight or more points indicates that the patients chances for recovery are good.

The ethical dilemma presented by persistent coma

When a patient has not suffered brain death (the complete absence of any electrical activity within the brain) but has been in a deep coma for some time, a change in condition may occur. This condition is called a persistent vegetative state. The patient may open his or her eyes and move his or her limbs in a

KEY TERMS

Anatomic Related to the physical structure of an organ or organism.

Ethical Referring to a system of values that provides the criteria for right behavior.

Metabolic Related to the chemical processes of an organ or organism.

Neuron The cells within the body that make up the nervous system.

Physiological Pertaining to the functioning of an organ, as governed by its physical and chemical condition.

Psychological Pertaining to the mind and its mental processes.

Stimulus An action performed on an individual that predictably provokes a reaction.

primitive fashion, demonstrating some degree of arousal. However, the patient lacks any element of awareness and is unable to have any measurably meaningful interactions with the surrounding world. This condition may last for years. The care of these patients has sparked some of the most heated debates within the field of medical ethics. The discovery of medical advances that allow various disease states to be arrested, without restoration of lost brain function, and the fact that medical resources are limited, have led to debates regarding when medical help should be withdrawn from an individual who has no hope of recovery.

See also Brain; Nervous system; Neuron; Psychology; Stimulus.

Resources

BOOKS

Al-Chalabi, Ammar. The Brain: A Beginners Guide. Oxford, UK: Oneworld, 2006.

Bear, Mark, F. Neuroscience: Exploring the Brain. Philadelphia, PA: Lippincott Williams & Wilkins, 2007.

Hains, Bryan C. Brain Disorders. Philadelphia, PA: Chelsea House Publishers, 2006.

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

Wilkinson, Iain M.S. Essential Neurology. Malden, MA: Blackwell Publishing, 2005.

Rosalyn Carson-DeWitt

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Coma

Coma

Definition

Coma, from the Greek word koma, meaning deep sleep, is a state of extreme unresponsiveness, in which an individual exhibits no voluntary movement or be-havior. Furthermore, in a deep coma, even painful stimuli (actions which, when performed on a healthy individual, result in reactions) are unable to cause any response, and normal reflexes may be lost.

Description

The important characteristics of the conscious state is defined by two fundamental elements: awareness and arousal.

Awareness allows one to receive and process all the information communicated by the five senses. Awareness has both psychological and physiological components. The psychological component refers to an individual's mind and mental processes. The physiological component refers to the functioning of an individual's brain, and the physical and chemical condition of the brain. Awareness is regulated by cortical areas within the cerebral hemispheres, the outermost layer of the brain.

Arousal is regulated solely by physiological functioning and consists of more primitive responsiveness to the world, as demonstrated by predictable reflex (involuntary) responses to stimuli. Arousal is maintained by the reticular activating system (RAS), a network of brain structures, including the brainstem, the medulla, and the thalamus, and nerve pathways that function together to produce and maintain arousal.

Causes and symptoms

Coma is the result of something that interferes with the functioning of the cerebral cortex and/or the functioning of the structures that comprise the RAS. Several conditions can result in coma. Anatomic causes of coma are those conditions that disrupt the brain structures responsible for consciousness, either at the level of the cerebral cortex or the brainstem, while metabolic causes of coma consist of those conditions that change the chemical environment of the brain, thereby adversely affecting function.

There are many metabolic causes of coma, including:

  • a decrease in the delivery to the brain of substances necessary for appropriate brain functioning, such as oxygen, glucose (sugar), and sodium
  • hyperglycemia, a condition in which blood sugar levels rise too high and remain dangerously high or hypoglycemia, in which blood sugar levels are too low and remain that way for a prolonged period of time.
  • the presence of certain substances such as drugs, alcohol, carbon dioxide, and ketones that disrupt the functioning of neurons
  • changes in chemical levels in the brain caused by seizures

Anatomic causes of coma include:

  • Physical trauma to the brain as a result of a motor vehicle or sports related accident or a near drowning can result in coma. Such injuries usually involve trauma to the brain including fractures or lack of oxygen.
  • A stroke or brain tumor. Although these conditions are not the result of physical trauma they nonetheless affect the brainstem. For instance, a coma often results when an individual suffers a stroke at the base of the brain.

Common signs and symptoms of a coma include:

  • failure to be aroused
  • eyes remain closed, however, in some cases the eyes move peculiarly
  • no response to external stimuli

Diagnosis

History and examination form the cornerstone of diagnosis when an individual is in a coma. However, history must be obtained from family, friends, or emergency medical service personnel.

The Glasgow Coma Scale is a system of examining a comatose person. It evaluates the depth of the coma, tracks the person's progress, and predicts the ultimate outcome of the coma. The Glasgow Coma Scale assigns a different number of points for exam results in three different categories: opening the eyes, verbal response, and motor response (moving a part of the body). Fifteen is the largest possible number of total points, indicating the highest level of functioning, which would be demonstrated by individuals who spontaneously open their eyes, give appropriate answers to questions about their situations, and can carry out a command such as moving a specific limb when ordered. Three is the least possible number of total points, and would be given to a person for whom not even a painful stimulus is sufficient to provoke a response. In the middle are those people who may be

able to respond, but who require an intense or painful stimulus, and whose response may demonstrate some degree of brain malfunctioning. When performed as part of the admission examination, a Glasgow score of three to five points often suggests that an individual has likely suffered fatal brain damage, while eight or more points indicates that the person's chances for recovery are good.

Expansion of the pupils and respiratory pattern are also important. Metabolic causes of coma are diagnosed from blood work and urinalysis to evaluate blood chemistry, drug screen, and blood cell abnormalities that may indicate infection. Anatomic causes of coma are diagnosed from computed tomography (CT), magnetic resonance imaging (MRI), or electroencephalography (EEG) scans.

Treatment

Coma is a medical emergency, and attention must first be directed to maintaining an individual's respiration and circulation, using intubation and ventilation, administration of intravenous fluids or blood as needed, and other supportive care. If head trauma has not been excluded, the neck should be stabilized in the event of fracture. It is extremely important for a physician to quickly determine the cause of a coma, so that potentially reversible conditions are immediately treated. These conditions may include an infection that can be treated with antibiotics , a brain tumor that can be removed, or brain swelling that can be reduced with certain medications.

Various metabolic disorders can be addressed by supplying an individual with the correct amount of oxygen, glucose, or sodium , by treating the underlying problem in liver disease, asthma , or diabetes, and by halting seizures with medication. Because of their low incidence of side effects and potential for prompt reversal of coma in certain conditions, glucose, the B-vitamin thiamine, and Narcan (to counteract any narcotic-type drugs) are routinely given.

Prognosis

Some conditions that cause coma can be completely reversed, restoring an individual to an original level of functioning. However, if areas of the brain have been sufficiently damaged due to the severity or duration of the condition that led to the coma, an individual may recover with permanent disabilities, either physical or mental, or may never regain consciousness. Short of death , the most severe types of brain injury result in states in which an individual loses all ability to function and remains deeply unresponsive. An individual who has suffered such a severe brain injury may remain in a coma indefinitely. This condition is termed a persistent vegetative state .

KEY TERMS

Anatomic —Related to the physical structure of an organ or organism.

Metabolic —Refers to the chemical processes of an organ or organism.

Narcan —A drug that reverses the effects of narcotics.

Neuron —The cells within the body which comprise the nervous system.

Reticular activating system (RAS) —A network of structures, including the brainstem, medulla, and thalamus, and nerve pathways, which function together to produce and maintain arousal.

Stimulus —Action performed on an individual that predictably provokes a reaction.

Outcome from a coma is therefore quite variable and depends a great deal on the cause and duration of the coma. In the case of drug poisonings, extremely high rates of recovery can be expected following prompt medical attention. Persons who have suffered head injuries tend to do better than do those whose coma was caused by medical illness. Besides those people whose coma results from drug poisoning, only about 15% of individuals who remain in a coma for more than just a few hours make a good recovery. Adult patients who remain in a coma for more than four weeks have almost no chance of eventually regaining their previous level of functioning. On the other hand, children and young adults have regained functioning after two months in a coma.

Caregiver concerns

Emergency medical team members are often first on the scene to provide a preliminary assessment of unconsciousness. In the hospital, a physician makes the diagnosis of coma, often with assistance from radiologists and laboratory technicians. Nurses provide supportive care throughout the duration of a coma. Physical therapists provide range of motion and other therapeutic movements designed to preserve normal muscular functioning.

Prevention

Medical conditions known to cause comas should be monitored and promptly treated. Applicable safety precautions and rules should be followed when engaging in any activity that has the potential for serious head injury .

Resources

periodicals

Dowdy, Mickey “A Comfortable Old Couch. (reflections) (Treating a patient from diabetic coma).” Diabetes Forecast 60.6 (May 2007): 80.

Mcauliffe, Kathleen “The Will To Live.” Prevention 59.8(August 2007): 182.

“Research Brief: Slow Therapy Best in Diabetic Coma. (Brief article).” GP (April 6 2007): 02.

organizations

American Academy of Neurology, 1080 Montreal Ave., St. Paul, MN, 55116, (651) 695–1940, (651) 695–2791, [email protected], http://www.aan.org.

Brain Injury Association, 105 North Alfred St., Alexandria, VA, 22314, (703) 236–6000, (800) 444–6443, [email protected], http://www.biausa.org/Sportsfs.htm.

Brain Trauma Foundation, 523 East 72nd St.,8th Floor, New York, NY, 10021, (212) 772–0608, http://www.braintrauma.org.

Coma Recovery Association, Republic Airport, Ste. 106, Farmingdale, NY, 11735, (631) 756–1826, http://www.comarecovery.org.

International Brain Injury Association, 1150 South Washington St., Ste. 210, Alexandria, VA, 22314, (703) 683–8400, [email protected], http://www.internationalbrain.org.

NIH Neurological Institute, PO Box 5801, Bethesda, MD, 20824, (800) 352–9424, http://www.ninds.nih.gov.

L. Fleming Fallon Jr., M.D., Dr.P.H.

Lisa M. Piazza M.A.

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Coma

Coma

Coma, from the Greek word koma, meaning deep sleep , is a state of extreme unresponsiveness in which an individual exhibits no voluntary movement or behavior . In a deep coma, stimuli, even painful stimuli, are unable to effect any response. Normal reflexes may be lost.

Coma lies on a spectrum with other alterations in consciousness. The level of consciousness which you, the reader, are currently enjoying is at one end of the spectrum, while complete brain death is at the other end of the spectrum. In between are such states as obtundation, drowsiness, and stupor, which all allow the individual to respond to stimuli, though such response may be brief and require a stimulus of greater than normal intensity.


Consciousness

In order to understand the loss of function suffered by a comatose individual, consider the important characteristics of the conscious state. Consciousness is defined by two fundamental elements: awareness and arousal.

Awareness allows us to receive and process information communicated by the five senses and thereby relate to ourselves and the rest of the world. Awareness has psychological and physiological components. The psychological component is governed by an individual's mind and its mental processes. The physiological component refers to the functioning—the physical and chemical condition—of an individual's brain. Awareness is regulated by areas within the cerebral hemispheres, the outermost layer of the brain, which separates humans from other animals because it allows greater intellectual functioning.

Arousal is regulated solely by physiological functioning. Its primitive responsiveness to the world is demonstrated by predictable reflex (involuntary) responses to stimuli. Arousal is maintained by the reticular activating system (RAS). This is not an anatomical area of the brain but rather a network of structures (including the brainstem, the medulla, and the thalamus) and nerve pathways which function together to produce and maintain arousal.


Causes of coma

Coma is the result of something which interferes with the functioning of the cerebral cortex and/or the functioning of the structures which make up the RAS. The number of conditions which could result in coma is mind-boggling. A good way of categorizing these conditions is to consider the anatomic and the metabolic causes of coma. Anatomic causes of coma are those conditions which disrupt the normal physical architecture of the brain structures responsible for consciousness. Metabolic causes of coma consist of those conditions which change the chemical environment of the brain and thereby adversely affecting function.

Anatomic causes of coma include brain tumors, infections, and head injuries. All three types of condition can affect the brain's functioning by actually destroying brain tissue . They may also affect the brain's functioning by taking up too much space within the skull. The skull is a very hard, bony structure which is unable to expand in size. If something within the skull begins to require more space (for example an expanding tumor or an injured/infected area of the brain which is swelling) other areas of the brain are compressed against the hard surface of the skull, which results in damage to these areas.

There are many metabolic causes of coma, including the following: (1) A decrease in the delivery of substances necessary for appropriate brain functioning, such as oxygen , glucose, and sodium . (2) The presence of certain substances disrupting the functioning of neurons. Drugs or alcohol in toxic quantities can result in neuronal dysfunction, as can some substances normally found in the body, but which accumulate at toxic levels due to some disease state. Accumulated substances which might cause coma include ammonia due to liver disease, ketones due to uncontrolled diabetes, or carbon dioxide due to a severe asthma attack. (3) The changes in chemical levels in the brain due to the electrical derangements caused by seizures.

Outcome

It is extremely important for a physician to quickly determine the cause of a coma, so that potentially reversible conditions are treated immediately. For example, an infection may be treated with antibiotics , a brain tumor may be removed, brain swelling from an injury can be reduced with certain medications. Furthermore, various metabolic disorders can be addressed by supplying the individual with the correct amount of oxygen, glucose, or sodium, by treating the underlying disease in liver disease, asthma, or diabetes, and by halting seizures with medication.

Some conditions which cause coma can be completely reversed, restoring the individual to his or her original level of functioning. However, if areas of the brain have been sufficiently damaged because of the severity or duration of the condition which led to the coma, the individual may recover from the coma with permanent disabilities, or may never regain consciousness. Take the situation of someone whose coma was caused by brain injury in a car accident. Such an injury can result in one of three outcomes. In the event of a less severe brain injury, with minimal swelling, an individual may indeed recover consciousness and regain all of his or her original abilities. In the event of a more severe brain injury, with swelling which results in further pressure on areas of the brain, an individual may regain consciousness, but with some degree of impairment. The impairment may be physical, such as paralysis of a leg, or result in a change in the individual's intellectual functioning and/or personality. The most severe types of brain injury result in states in which the individual loses all ability to function and remains deeply unresponsive. An individual who has suffered such a brain injury may remain in a coma indefinitely.

Outcome from a coma depends on its cause and duration. In drug poisonings, extremely high rates of recovery can be expected, following prompt medical attention. Patients who have suffered head injuries tend to do better than patients whose coma was caused by other types of medical illnesses. Excluding drug-poisoning induced comas, only about 15% of patients who remain in a coma for more than a few hours make a good recovery. Adult patients who remain in a coma for more than four weeks have almost no chance of regaining their previous level of functioning. However, children and young adults have regained functioning after two months in a coma.


Glasgow Coma Scale

The Glasgow Coma Scale, a system of examining a comatose patient, can be helpful for evaluating the depth of the coma, tracking the patient's progress, and possibly predicting ultimate outcome of the coma. The Glasgow Coma Scale assigns a different number of points for exam results in three different categories: opening the eyes, verbal response (using words or voice to respond), and motor response (moving a part of the body). Fifteen indicates the highest level of functioning. An individual who spontaneously opens his or her eyes, gives appropriate answers to questions about his or her situation, and can follow a command (such as "move your leg," "nod your head") has the highest level of functioning. Three is the smallest possible number of points, and would be given to a patient who is unresponsive to a painful stimulus. In the middle are those patients who may be able to respond, but who require an intense or painful stimulus, and whose response may demonstrate some degree of brain malfunctioning. When performed as part of the admission examination, a Glasgow score of three to five points suggests that the patient likely has suffered fatal brain damage, while eight or more points indicates that the patient's chances for recovery are good.

The ethical dilemma presented by persistent coma

When a patient has not suffered brain death (the complete absence of any electrical activity within the brain) but has been in a deep coma for some time, a change in condition may occur. This condition is called a persistent vegetative state. The patient may open his or her eyes and move his or her limbs in a primitive fashion, demonstrating some degree of arousal. However, the patient lacks any element of awareness and is unable to have any measurably meaningful interactions with the surrounding world. This condition may last for years. The care of these patients has sparked some of the most heated debates within the field of medical ethics. The discovery of medical advances that allow various disease states to be arrested, without restoration of lost brain function, and the fact that medical resources are limited, have led to debates regarding when medical help should be withdrawn from an individual who has no hope of recovery.

See also Nervous system; Neuron; Psychology; Stimulus.


Resources

books

Guberman, Alan. An Introduction to Clinical Neurology. Boston: Little, Brown, 1994.

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

Liebman, Michael. Neuroanatomy Made Easy and Understandable. Baltimore: University Park Press, 1991.


Rosalyn Carson-DeWitt

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Anatomic

—Related to the physical structure of an organ or organism.

Ethical

—Referring to a system of values that provides the criteria for right behavior.

Metabolic

—Related to the chemical processes of an organ or organism.

Neuron

—The cells within the body that make up the nervous system.

Physiological

—Pertaining to the functioning of an organ, as governed by its physical and chemical condition.

Psychological

—Pertaining to the mind and its mental processes.

Stimulus

—An action performed on an individual that predictably provokes a reaction.

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