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Neurosurgery

Neurosurgery

Definition

Neurosurgery is a specialized field of surgery for the treatment of diseases or conditions of the central nervous system (CNS) and spine.


Description

Neurosurgery is the specialized field of surgery that treats diseases that affect the CNSthe brain and the spine. A neurosurgeon is a medical doctor who has received extensive training in the surgical and medical management of neurological diseases. The field of neurosurgery is one of the most sophisticated surgical specialties and encompasses advanced surgical and imaging technology and new research in molecular neurosurgery and gene therapy. There are five general categories of neurosurgical diseases that are commonly managed by neurosurgeons: cerebrovascular (hemorrhage and aneurysms); traumatic head injury (THI)(traumatic injury caused by accident); degeneration diseases of the spine; tumors in the CNS; functional neurosurgery; surgery for congenital abnormalities; and neurosurgical management of the CNS.

Cerebrovascular diseases that usually require surgery include spontaneous intracranial hemorrhage, spontaneous subarachnoid hemorrhage, spontaneous intracerebral hemorrhage, cerebral aneurysms, hypertensive intracerebral hemorrhage, and angiomatous malformations.


Brain hemorrhage

Spontaneous intracranial hemorrhage (hemorrhage in the brain) is a condition characterized by hemorrhage in the brain (hemorrhagic stroke) that results in a sudden onset of neurologically worsening symptoms (that include focal neurologic deficits and loss of consciousness). CT scans are helpful in identifying the intracranial hemorrhage, of which there are two typessubarachnoid hemorrhage and intracerebral hematoma.

The subarachnoid space is an area that exists between two layers of coverings (membranes) that wrap around the brain. A spontaneous subarachnoid hemorrhage is defined as blood (not caused by trauma), in the subarachnoid space. The amount of blood in the subarachnoid space can be a focal (small area) amount or a larger, more diffuse hemorrhage, which can be further complicated by having an intraventricular hemorrhage or intracerebral hematoma at the same time. Subarachnoid hemorrhage can affect adults of all ages, but usually peaks in the fourth and fifth decades of life. Approximately 60% of patients are female.

The incidence of subarachnoid hemorrhage is 10 per 100,000 persons per year; approximately 30% of Americans will sustain a subarachnoid hemorrhage annually. The most frequent cause of spontaneous subarachnoid hemorrhage is rupture of an intracranial aneurysm. The symptoms of subarachnoid hemorrhage are characterized by a sudden onset of severe headache that worsens over time, and includes nausea, loss of consciousness (with or without seizure) and vomiting. Depending on the extent of the bleed, symptoms of subarachnoid hemorrhage can also include visual sensitivity to light (photophobia), a stiff neck, and minor (low grade) fever. Symptoms before rupture of the aneurysm occur in 40% of persons and are usually due to minor subarachnoid hemorrhage. These symptoms can also include headache or dizziness, and tend to go unnoticed.

Approximately 30% of subarachnoid hemorrhages occur during sleep. Smoking is a major factor in increasing the odds of sustaining a subarachnoid hemorrhage. After a subarachnoid hemorrhage, most patients are hypertensive and experience changes in cardiac rate and rhythm. CT scans are the best diagnostic tool for subarachnoid hemorrhage and are positive in the first 24 hours after the hemorrhage has been experienced in 90% of patients and in more than 50% in the first week. Spinal taps to sample the cerebrospinal fluid (CSF) may be required to evaluate some patients who have the potential to suffer a subarachnoid hemorrhage. This involves the insertion of a thin needle between the lumbar vertebral bodies (L4 and L5) to allow the removal of a small amount of fluid to look for either red or white blood cells (WBCs). Once the aneurysm has been identified, the patient is taken for surgery. A craniotomy is performed using microsurgical techniques. The operative microscope helps to identify the aneurysm, which is then clipped. Berry, or congenital aneurysm, is the reason for over half of all cases of spontaneous subarachnoid hemorrhage.

A spontaneous, intracerebral hemorrhage (SICH) is a blood clot in brain tissue that can arise abruptly and is strongly correlated with hypertension. There are approximately 40,000 new cases of SICH in the United States annually. Stroke is the third leading cause of death in the United States, and SICH accounts for 10% of all stroke cases. Advancing age is a major predisposing factor for SICH: The incidence of SICH is two per 1,000 persons per year by age 45, and a person aged 80 years or more has a 350 per 100,000 persons per year incidence. Hypertensive intracerebral hemorrhage can occur in different areas within the brain. Damage to some areas may be associated with a very high death rate. Treatment includes comprehensive ICU (intensive care unit ) management of hypertension and maintenance of adequate cerebral perfusion (oxygenated blood going to the brain).

Accidents that result in head injury are a major public health problem. Trauma causes approximately 150,000 deaths annually in the United States; approximately half of these deaths were caused by fatal head trauma. Additionally, there are 10,000 new spinal cord injuries annually. The cost of disability (e.g., chronic long-term care, lost wages and work) is very high. Approximately 200,000 persons in the United States are living with disabilities associated with head and spinal cord trauma.

Severe head injury is defined as an injury that produces coma (patient will not open eyes even to painful stimulus; incapable of following simple commands; and inability to utter words). These clinical criteria are defined on the well-established Glasgow Coma Scale (GCS). A physical examination and neurologic assessment by a neurosurgeon and brain scan imaging (CT scan) is necessary for the initial evaluation. Additionally, a special catheter to monitor intracranial pressure (due to brain swelling) is inserted. A large clot, larger than 25 to 30 cubic centimeters, is considered clinically large enough to cause progressive brain injury.

Tumors inside the brain (intracranial tumors) are typically of two types; primary and secondary intracranial tumors. Primary intracranial tumors (PICT) rarely metastasize and usually originate in the brain, coverings (membranes) of the brain, or the pituitary gland. The incidence of primary intracranial tumors is 11.5 per 100,000, or approximately 35,000 persons per year.

Secondary intracranial tumors arise from outside the brain coverings (meninges). Quite commonly, secondary intracranial tumors are blood-borne metastatic disease from primary malignant cancer outside the brain (i.e., cancer from some other location that has spread to the brain). Approximately 250,000 persons per year are affected by secondary intracranial tumors. A tumor in the brain can present clinically with symptoms of increased intracranial pressure, or with symptoms associated with compression of the brain (a tumor grows and compresses part of the brain against the skull). One common cause of increased intracranial pressure is growth of a tumor that obstructs the duct system of cerebrospinal fluid (CSF), which bathes and nourishes the brain and spinal cord. Common symptoms can include nausea, vomiting, headache that is worse in the morning, and a reduced level of consciousness that causes drowsiness. Tumors causing focal compression on or irritation of the brain usually result in loss of neurologic function. This progressive loss of neurologic function can manifest as tinnitus (ringing in the ears) or aphasia (language problems).

Technical improvements and advancement have made surgical removal of brain tumors more effective and safer. Surgical management of intracranial tumors focuses on diagnosis and reduction of tumor mass. Depending on tumor location and patient health status, the neurosurgeon may perform a needle biopsy (called image-directed stereotactic needle biopsy) or a craniotomy to extract a piece of tumor for pathologic analysis. Generally, if the tumor is located in an area where surgery can be performed, the neurosurgeon will remove the mass if the patient can tolerate general anesthesia. Exceptions to a surgical option may be exercised to treat malignant tumors that are very sensitive to chemotherapy or radiation therapy (i.e., to manage lymphoma or germinoma). One of the most common types of tumors is the glioma, which accounts for 50% of all primary brain tumors.


Degenerative disorders of the spine

Degenerative disorders of the spine are a common problem. Between 50% and 90% of the population will experience back pain at some point in their lifetime. However, most of these back pain symptoms subside on their own within a few weeks; the cost, however, results in decreased productivity and lost wagesa public health problem. Lower back pain (in the lumbar spine) is most common reason adults seek medical attention. In a normal person, the lumbar spine comprises five lumbar vertebra. The lumbar spine supports the weight of the entire column and, therefore, withstands a great load. Lower back disorders are among the most frequent reasons for referral to a neurosurgeon. Lumbar discs are very prone to herniation and desiccation (drying out) as a result of the heavy load they bear and the motion to which they are subject. Nerves that run from the vertebrae extend out to distant structures. Degeneration of the discs may change bony structures in such a manner that can cause nerve compression. Typically, persons with degenerative disorders of the spine may have pain, numbness, paresthesia (tingling), and restriction of neck movement (if the affected vertebrae is in the cervical spine, which is located in the back of the neck).


Surgery for congenital abnormalities

Congenital abnormalities occur during embryonic development. During development of the human embryo, important changes in growth and chemistry occur during the second week of gestation; these changes contribute to the development of the nervous system. Several different types of cells proliferate as they move together or separate into other structures according to an orchestrated, natural time clock. Defects can occur at different stages of development. The defects with which infants can be born include myelomeningoceles, encephaloceles, hydrocephalus, and craniosynostosis.

Central nervous system infections

Solitary or multiple brain abscesses can occur as a result of infection in the brain. Patients present with clinical symptoms such as focal (a specific area is affected) neurologic signs, seizures, altered mental status, and increased intracranial pressure. CT scans and magnetic resonance imaging (MRI) are helpful for identification of brain abscesses. Surgery is usually indicated if the abscess fails to resolve or worsens following antibiotic treatment, or if there are signs of mass effect and brain herniation. Although rare, a spinal epidural abscess can occur. Typically, bacteria can spread in patients who have acute bacterial meningitis (infection of the subarachnoid spaces and meninges). The specific type of bacteria varies according to the patient's age.


Functional neurosurgery

Functional neurosurgery is a special type of surgical procedure used to manage movement disorder, epilepsy, and pain. Stereotactic neurosurgery makes use of a coordinate system that provides accurate navigation to a specific point or region in the brain. This is usually done by placing and fixing into position a frame on the scalp (using four threaded pins that penetrate the outer skull to stabilize the frame in position) under local anesthesia. A special box and sterotactic arc are placed to precisely determine X, Y, and Z coordinates of any point within the frame.


Epilepsy surgery

Approximately 70 per 100,000 population in the United States take antiepileptic medications for seizure disorders. The risk of developing epilepsy over a lifetime is 3%, and there are 100,000 new cases per year. The majority of cases (approximately 60,000) are temporal lobe (the brain lobes located on the sides of the head) epilepsy. Approximately 25% of persons prescribed antiepileptic drugs for temporal lobe seizures are not controlled or the side effects of the drug are far too great and outweigh the therapeutic benefits. Approximately 5,000 new cases per year require epilepsy surgery (partial anterior temporal lobectomy). The patient and neurosurgeon should consider surgery if continual seizures cause injuries due to repeated falls; driving restrictions; limitation of social interactions; problems related to education and learning; and employment limitations.


The future of neurosurgery

Neurosurgery as a field is faced with many new opportunities and challenges, based on advanced technological approaches and molecular approaches to neurosurgical problems. Advances in technology have allowed the neurosurgeon to precisely locate abnormal tissue in the brain and spinal cord, thereby preserving normal tissues from surgical trauma. In addition to cardiovascular neurosurgery, functional neurosurgery, neuro-oncologic neurosurgery (surgical removal of brain tumors), and spinal surgery, the future holds many new research innovations. In the new millennium, the field of molecular neurosurgery can make it possible to introduce genetic material into nerve cells and to redirect protein synthesisto work toward reversing the disease process, in general.

Resources

books

Miller. E. Anesthesia, 5th Ed. Philadelphia, PA. Churchill Livingstone, Inc., 2000.

Townsend, C. Sabiston. Textbook of Surgery, 16th Ed. Philadelphia, PA. W. B. Saunders Company, 2001.

periodicals

Freese, A., Simeone, F. "Ocular Surgery for the New Millennium." and "Treatment of Neurosurgical Disease in the New Millennium." Ophthalmology Clinics of North America 12, no.4 (December 1999).

organizations

The American Board of Neurological Surgery. 6550 Fannin Street, Suite 2139 Houston, TX 77030. (713) 441-6015. <http://www.abns.org>.


Laith Farid Gulli, M.D.,M.S.
Miguel A. Melgar, M.D.,Ph.D.
Nicole Mallory, M.S.,PA-C

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?


A neurosurgeon performs the procedure in a major hospital. The neurosurgeon is a medical doctor who has obtained two years of general surgery training, plus an additional five years of training in neurosurgery.

QUESTIONS TO ASK THE DOCTOR


  • What the potential side effects that can arise as a result of surgery?
  • How likely are complications to develop?
  • How long will recovery take?
  • Will I undergo rehabilitation, and if so, for how long?

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neurosurgery

neu·ro·sur·ger·y / ˌn(y)oŏrōˈsərjərē/ • n. surgery performed on the nervous system, esp. the brain and spinal cord. DERIVATIVES: neu·ro·sur·geon / ˈn(y)ərōˌsərjən/ n. neu·ro·sur·gi·cal / -jikəl/ adj.

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neurosurgery

neurosurgery (newr-oh-ser-jer-i) n. the surgical or operative treatment of diseases of the brain and spinal cord.

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Neurosurgery

Neurosurgery

Application of neurosurgery

Diagnosis

Advances in neurosurgery

Intraoperative guidance systems

Resources

Neurosurgery, sometimes also called neurological surgery, is a medical specialty concerned with the diagnosis and treatment of the central and peripheral nervous system. It also involves the surgical operations on the brain and spinal column. These procedures involve such activities as cutting out tumors from the brain and repairing slipped discs in the spine.

The nervous system is composed of the brain, spinal cord and spinal column, as well as the nerves that travel through all parts of the body (hands, legs, arms, face). Neurosurgeons treat degenerative and congenital diseases of the spine, pain from pinched nerves in the neck, lower back pain, sciatica, carpal tunnel syndrome, epilepsy, stroke, Parkinson disease, chronic pain and sports injuries of the head and spine, in addition to brain tumors, hemorrhages and trauma, tumor of the pituitary gland, and disorders of the arteries that carry blood from the heart to the brain. The field of neurosurgery encompasses both adult and pediatric patients. Neurosurgery has one of the longest training periods of any medical specialty due to the extreme complexity of the nervous system and the advanced techniques used in neurosurgical operations.

Neurosurgery may have begun in the early stages of human evolution. Skulls of early humans show signs of incision through the bone. Some skulls have as many as five openings cut into them. Some of this ritual was probably for magical purposes and some was medicinal, performed to release the spirits that were causing excruciating headaches or making an individual show signs of insanity, or to remove bone fragments resulting from trauma. This process is called trephination (less commonly, trepanation) and was a common procedure as early as the Neolithic period. Interestingly, this procedure was done in human settlements around the world. These clans or tribes had no contact with each other, yet they devised and practiced a similar procedure as a form of spiritual or medical therapy.

Trephining was accomplished with a sharpened flint moved in rapid circular motions to cut through the bony skull. The procedure took about a half hour on a drugged patient. It is likely that early humans had discovered the means to immobilize an individual so that surgery could be carried out. Trephining was practiced as late as the mid-twentieth century among isolated peoples. Even cadavers were trephined to remove bone fragments, which were then worn as amulets.

Needless to say, the survival rate of trephination was low. However, skulls have been found that show bone growth around the edges of the opening, indicating that the patient survived for a time after the procedure. More often, skulls with trephined openings show the raw, incised edges of the operative area, indicating that the patient probably died during surgery or shortly thereafter. Infection was not understood and was a high probability following surgery in such conditions.

It was not until the late nineteenth century that further progress was made in the field of neurosurgery. In November 1884, two British surgeons, Alexander Hughes Bennett (18481901) and Richman John Godlee (18491925), operated to remove a brain tumor. Shortly thereafter, in 1888, English scientist Sir Victor Horsley (18571916) removed a tumor from the spinal cord of one of his patients. That same year American surgeon William Williams Keen (18371932), of Philadelphia, Pennsylvania, removed a meningioma, a hard, slow-growing tumor that grows on one of the membranes covering the brain. In 1889, Keen tapped the ventricles of the brain, the small openings at the base of the brain where fluid collects.

The development of the x ray provided a means for neurosurgeons to find tumors growing in the brain, bone splinters, or other foreign objects. Still, it remained difficult to locate these growths precisely enough for surgical removal. The invention of stereo-tactic frames to provide precise guidance to underlying tumors helped revolutionize surgery on the brain.

Application of neurosurgery

Current neurosurgery includes trephination along with other procedures to correct not only injury and disease of the central nervous system, but also to modify nerve supply to other areas of the body that may benefit from such surgery and to enhance blood supply to the brain. A number of conditions are commonly treated by neurosurgery. Injuries of the skull, brain, vertebral column and spinal cord are common diagnoses in neurosurgery and are most commonly caused by motor vehicle accidents or sports accidents.

Injury to the head or spinal column may result in swelling of the enclosed nervous tissues, bleeding inside the skull that would place pressure on a localized area of the brain, or may involve bone fragments impinging on the brain or spinal cord as a result of a blow to the head or back. Certain congenital conditions such as hydrocephalus (excessive fluid on the brain) or spina bifida (a condition in which the spine has not closed around the spinal cord) frequently are treated by the neurosurgeon. Premature closure of the skull, which will prevent the skull from expanding as the brain grows, also requires surgery to separate the skull bones.

Tumor growth in the skull or spinal column may also require surgical correction. A benign (non-cancerous) tumor in the brain is usually well defined and can be removed by delicate surgery. A malignant (cancerous) tumor presents a much more challenging problem because it is not defined as clearly and may contain a benign growth as well. Still, some areas of the brain remain unreachable by surgical tools and a growth in those areas cannot be removed. In that case, the physician may resort to radiation therapy or the use of anti-tumor drugs.

The brain requires an especially copious blood supply. Large arteries in the side and back of the neck carry blood to the brain, but when these arteries become narrowed or blocked by fatty deposits (a condition called atherosclerosis), the blood supply to the brain may be reduced to an insufficient amount. A balloon catheter may be used by the physician to clear the blockage. In this procedure, called angiography, a catheter is guided to the site of blockage. The tiny balloon on the end of the catheter is inflated to press the blockage out of the way. The balloon is then deflated, and the catheter removed. In the event this procedure is not effective, the surgeon may need to operate on the blood vessels instead of the brain itself. A graft to bypass the blocked area may be called for or the vessel may be opened and the deposit removed (a procedure called endarterectomy) if the artery is accessible. In addition, an artery can balloon from the pressure of the blood within it. This is called an aneurism, and it forms at the site of a weak spot in the arterial wall. The swollen artery in itself may do no harm, but the weakened arterial wall can burst at any time, allowing the escape of blood into the brain. This is one form of stroke. If the artery is accessible, the surgeon can remove the weak area and sew the ends of the artery together again. If the artery cannot be reached for surgical correction, some means can be taken to reinforce the arterial wall from within.

A so-called slipped disk or ruptured disk, damage to one of the cartilaginous disks between the vertebrae, may form a protrubance into the spinal canal that impinges on the spinal cord. This may cause pain or even the inability to walk normally. Here again, the neurosurgeon may need to take steps to remove the protrusion and in some cases fuse the vertebrae to prevent their flexing on the weakened disk.

In cases of intractable pain or involuntary movements that cannot be corrected, the surgeon may be called upon to interrupt the nerve supply to a given area. This function is being taken over more and more by medical therapy as physicians learn new information about nerve functions and how to interrupt them medicinally, but the surgeon still provides a needed service.

Locating a tumor or area in which blood has been released inside the skull requires a rigorous diagnostic procedure. If the patient has had an accident such as a fall or automobile wreck in which he/she struck his/her head, the surgeon may be more aware of the possibility of the existence of a blood clot forming on the brain, bone fragments that may be impinging on the brain, or swelling of the brain. If the patient denies any accidental trauma to the head, but has had persistent and longstanding headaches, visual disturbances, dizziness, or other lingering symptoms, the surgeon is alerted to the possibility of an aneurism or other source of blood leakage or a developing tumor.

Diagnosis

The diagnosis of the source of a brain disorder has become infinitely more precise with the modern technology of computerized tomography (CT) and magnetic resonance imaging (MRI) scans. Either of these scans shows several views of the brain and the presence of a tumor, excessive fluid build-up, or intracranial bleeding. They also provide the means for precise measurement of the depth of the growth and its angle from various landmarks on the skull. This enables the neurosurgeon to use a stereotactic frame to guide his instruments precisely to the site of the lesion.

The CT or MRI scan shows a cross section of the brain at a certain level. Each exposure is slightly advanced from the previous one. In all, the images appear to be slices of the brain that show various details at each level. The computer control also allows the images to be combined to form a three-dimensional image so the physician can see the tumor or damaged area of the brain in relation to the complete structure. In this way, the surgeon can decide whether the patient is a candidate for surgery or whether the tumor or other lesion is not accessible. The image also gives a good idea of whether the tumor is a cancerous lesion or is benign.

Advances in neurosurgery

Diagnostic accuracy allows the surgeon to work precisely where he or she wants to work with amazing efficiency and reliability, each and every time. The result is that the surgical incision has been reduced to an absolute minimum. Smaller incisions, less tissue trauma, and better surgical planning have reduced the overall risk of brain surgery from almost 90% in the 1940s to about less than 2% in the twenty-first century.

A groundbreaking medical advance of recent years, is the Leksell gamma knife. This revolutionary new treatment is a safe, effective, and cost-efficient alternative to conventional neurosurgery for certain patients. Developed in 1968 by Swedish professors Lars Leksell (19071986) and Borge Larsson, the gamma knife is a highly advanced instrument used to treat arteriovenous malformations (AVM), facial pain, benign and malignant brain tumors, and other functional brain disorders. What makes the gamma knife so unique is that it successfully treats these conditions with no incision. Instead, it uses a concentrated radiation dose from Cobalt-60 sources. A total of 201 beams of radiation intersect to form a powerful tool focused on a targeted area of abnormal tissue within the brain. The gamma knife is so precise that it damages and destroys the unhealthy tissue while sparing adjacent normal, healthy tissue.

Intraoperative guidance systems

Just as NASAs space shuttle is guided in mid-flight, so the hand of the surgeon can be guided in mid-operation. Stereotactic guidance systems (involving surface markers or frames, computers, etc.), three dimensional computer-assisted guidance systems (via infrared lights, lasers, mechanical arms, radiotelemetry), even real-time imaging such as intraoperative ultrasonic guidance systems and MRI, and finally computer-guided mechanical arms (hands free) are all available to todays surgeon.

Stereotactic surgery is the use of a special frame that attaches to the skull and serves to guide the surgeons instruments, electrodes, or cannulae precisely to a local area. The frame is called a stereoencephalotome, which combines the Greek words for solid, head, and to cut; thus, it is an instrument to cut through the solid head. In fact, the stereoencephalotome does no cutting. Instead, it is an instrument with a rounded frame that attaches to the patients head and can be used to guide instruments at precise angles into the brain.

Once the surgeon has located the area of the brain in which to operate, he/she places a stereotactic frame on the patients head. Several types of frame can be used, each of which differs in its type of orientation. Some frames must be oriented with a trephined opening in the skull. Others are oriented using landmarks on the skull such as the ear canals. Once the surgeon has placed the frame over the brain lesion he/she can position movable arms in the frame to guide electrodes or other instruments into the substance of the brain. Tissue destruction can interrupt pain pathways to reduce pain from cancer or other lesions, which helps the patient better cope with therapy. Certain diseases such as Parkinsonism or hyperkinesis, which involve involuntary movements or shaking can be helped by destroying a small area within the brain. Also, this method can be used to remove a blockage of the drainage system of the brain, which in turn allows the buildup of cerebrospinal fluid and causes hydrocephalus. Removing the tumor blocking the drainage canal or implanting a tube through the canal to drain the fluid relieves the pressure within the skull. Of course, foreign bodies such as bullets also can be located and removed. Precisely focused radiation can be guided by stereoframes to converge on the site of a tumor and destroy it.

As physicians learn more about the brain and the precise location of various functions within it, the use of stereotactic surgery grows. The brain is the only organ that can study itself, and it continues to accumulate knowledge that serves its own best interest in times of illness or injury. With current technology, scientists have begun the implantation of electrodes in the brain to allow the deaf to hear and the blind to see. The electrodes are threaded into the area of the brain that controls hearing or sight and then are connected through a computer to a light or sound receptor. Although this technique is in its early stages, progress in miniaturization of the hardware and the improved knowledge of brain structure and function are combining to make this field a promising venture for the near future.

See also Neuron; Neuroscience.

KEY TERMS

Cannula (plural: cannulae) A hollow tube inserted into an area of the body to drain fluid, guide an instrument, or provide a means to measure pressure or temperature.

Hyperkinesis Excessive movement or motor activity. A syndrome that results from a brain lesion and leads to fidgeting, nervousness, constant movement, short attention span, and other symptoms in adolescence.

Neolithic period The geological period that began approximately 12,000 years ago. It was during this period that humans developed advanced stone tools and began forming farming societies.

Neuro Refers to the nervous system, including the brain, spinal cord, or the nerves leading to and from them.

Resources

BOOKS

Barow, Daniel L., et al., eds. Fifty Years of Neurosurgery. Philadelphia, PA: Lippincott Williams & Wilkins, 2000.

Connolly, E. Sander, et al. Fundamental of Operative Techniques in Neurosurgery. New York: Thieme Medical Publishers, 2000.

Kaye, A. H. Brain Tumors: An Encyclopaedic Approach. Churchill Living, 2001.

Silver, John R. History of the Treatment of Spinal Injuries. New York: Kluwer Academic/Plenum Publishers, 2003.

PERIODICALS

Ganz, J.C. Gamma knife radiosurgery and its possible relationship to malignancy: a review. Journal of Neurosurgery. 2002 Dec; 97(5 Suppl):64452.

Levivier M, Wikler D Jr, Massager N, David P, Devriendt D, Lorenzoni J, Pirotte B, Desmedt F, Simon S Jr, Goldman S, Van Houtte P, Brotchi J. The integration of metabolic imaging in stereotactic procedures including radiosurgery: a review. Journal of Neurosurgery. 2002 Dec; 97(5 Suppl):54250.

Larry Blaser

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Neurosurgery

Neurosurgery

Definition
Description
The future of neurosurgery

Definition

Neurosurgery is a specialized field of surgery for the treatment of diseases or conditions of the central nervous system (CNS) and spine.

Description

Neurosurgery is the specialized field of surgery that treats diseases that affect the CNS—the brain and the spine. A neurosurgeon is a medical doctor who has received extensive training in the surgical and medical management of neurological diseases. The field of neurosurgery is one of the most sophisticated surgical specialties and encompasses advanced surgical and imaging technology and new research in molecular neurosurgery and gene therapy. There are five general categories of neurosurgical diseases that are commonly managed by neurosurgeons: cerebro-vascular (hemorrhage [bleeding] and aneurysms); traumatic head injury (THI, traumatic injury caused by accident); degeneration diseases of the spine; tumors in the CNS; functional neurosurgery; surgery for congenital abnormalities; and neurosurgical management of the CNS.

Cerebrovascular diseases that usually require surgery include spontaneous intracranial hemorrhage (bleeding within the skull), spontaneous subarachnoid hemorrhage (bleeding beneath the outer membranous covering of the brain), spontaneous intracerebral hemorrhage (bleeding within the brain), cerebral aneurysms (outpouchings of the blood vessel), hypertensive intracerebral hemorrhage (due to high blood pressure), and angiomatous malformations.

Brain hemorrhage

Spontaneous intracranial hemorrhage is a condition characterized by hemorrhage in the brain (hemorrhagic stroke) that results in a sudden onset of neurologically worsening symptoms (that include focal neurologic deficits and loss of consciousness). CT scans are helpful in identifying the intracranial hemorrhage, of which there are two types—subarachnnoid hemorrhage and intracerebral hematoma.

The subarachnoid space is an area that exists between two layers of coverings (membranes) that wrap around the brain. A spontaneous subarachnoid hemorrhage is defined as blood (not caused by trauma), in the subarachnoid space. The amount of blood in the subarachnoid space can be a focal (small area) amount or a larger, more diffuse hemorrhage, which can be further complicated by having an intra-ventricular hemorrhage or intracerebral hematoma at the same time.

The incidence of subarachnoid hemorrhage is 10 per 100,000 persons per year; approximately 30% of Americans will sustain a subarachnoid hemorrhage annually. Smoking is a major factor in increasing the odds of sustaining a subarachnoid hemorrhage.

KEY TERMS

Angiomatous malformations— Tumors in blood vessels.

Cerebral aneurysms —A sac in a blood vessel in the brain that can rupture and cause bleeding in the brain.

Craniosynostosis —Premature closure of the skull, which results in skull deformities.

Craniotomy —Procedure to remove a lesion in the brain through an opening in the skull.

Desiccation —Tissue death.

Encephaloceles— Protrusion of the brain through a defect in the skull.

Germinoma— A tumor of germ cells (ovum and sperm cells that participate in production of the developing embryo).

Hydrocephalus— A defect characterized by an increase in cerebrospinal fluid (CSF), which bathes and nourishes the brain and spinal cord.

Intraventricular hemorrhage— Hemorrhage in the ventricles of the brain.

Lymphoma— A tumor of lymph glands or lymph tissues.

Meninges— Membranes that cover the brain.

Myelomeningoceles (MMC)— A protrusion in the vertebral column containing spinal cord and meninges.

Subarachnoid space— A space between membranes that covers and protects the brain.

Subarachnoid hemorrhage can affect adults of all ages, but usually peaks in the fourth and fifth decades of life. Approximately 60% of patients are female. Approximately 30% of subarachnoid hemorrhages occur during sleep.

The most frequent cause of spontaneous subarachnoid hemorrhage is rupture of an intracranial aneurysm. The symptoms of subarachnoid hemorrhage are a sudden onset of severe headache that worsens over time, nausea, loss of consciousness (with or without seizure), and vomiting. Depending on the severity of bleeding, additional symptoms can also include visual sensitivity to light (photophobia), a stiff neck, and minor (low-grade) fever. Symptoms occur before rupture of the aneurysm in 40% of patients, usually in those with a minor hemorrhage. These symptoms can also include headache or dizziness, and tend to go unnoticed.

After a subarachnoid hemorrhage, most patients are hypertensive (have high blood pressure) and experience changes in heart rate and rhythm. CT scans are the best diagnostic tool for subarachnoid hemorrhage. The hemorrhage can be visualized in the first 24 hours after onset in 90% of patients and in more than 50% in the first week. Spinal taps to sample the cerebrospinal fluid (CSF) may be required to evaluate some patients who have the potential to suffer a subarachnoid hemorrhage. This procedure involves the insertion of a thin needle between the lumbar vertebral bodies (L–4 and L–5) to allow the removal of a small amount of fluid to look for either red or white blood cells (WBCs). Once the aneurysm has been identified, the patient is taken for surgery. A craniotomy is performed using microsurgical techniques. The operative microscope helps to identify the aneurysm, which is then clipped. Berry, or congenital aneurysm, is the reason for over half of all cases of spontaneous subarachnoid hemorrhage.

A spontaneous intracerebral hemorrhage (or hematoma) (SICH) is a blood clot in brain tissue that can arise abruptly and is strongly correlated with hypertension. There are approximately 40,000 new cases of SICH in the United States annually. Stroke is the third leading cause of death in the United States, and SICH accounts for 10% of all stroke cases. Advancing age is a major predisposing factor for SICH: The incidence of SICH is two per 1,000 persons per year by age 45, and rises to 350 per 100,000 persons per year in those aged 80 years or more. Hypertensive intracerebral hemorrhage can occur in different areas within the brain. Damage to some areas may be associated with a very high death rate. Treatment includes comprehensive ICU (intensive care unit ) management of hypertension and maintenance of adequate cerebral perfusion (oxygenated blood going to the brain).

Accidental head injury is a major public health problem. Trauma causes approximately 150,000 deaths annually in the United States; approximately half of these deaths were caused by fatal head trauma. Additionally, there are 10,000 new spinal cord injuries annually. The cost of disability (e.g., chronic long-term care, lost wages, and work) is very high. Approximately 200,000 persons in the United States are living with disabilities associated with head and spinal cord trauma.

Severe head injury is defined as an injury that produces coma (patient will not open eyes even to painful stimulus; incapable of following simple commands; and inability to utter words). These clinical criteria are defined on the well-established Glasgow Coma Scale (GCS). A physical examination and neurologic assessment by a neurosurgeon and brain scan imaging (CT scan) are necessary for the initial evaluation. Additionally, a special catheter to monitor intracranial pressure (due to brain swelling) is necessary. A blood clot larger than 25 to 30 cubic centimeters is considered clinically large enough to cause progressive brain injury.

Tumors inside the brain (intracranial tumors) are typically of two types, primary and secondary intracranial tumors. Primary intracranial tumors (PICT) rarely metastasize and usually originate in the brain, coverings (membranes) of the brain, or the pituitary gland. The incidence of primary intracranial tumors is 11.5 per 100,000, or approximately 35,000 persons per year.

Seonrary intracranial brain coverings (meninges). Quite commonly, secondary intracranial tumors are bloodborne metastatic disease from primary malignant cancer outside the brain (i.e., cancer from some other location that has spread to the brain). Approximately 250,000 persons per year are affected by secondary intracranial tumors. A tumor in the brain can cause increased intracranial pressure, or cause symptoms associated with localized compression of the brain (i.e., a tumor grows and compresses part of the brain against the skull). One common cause of increased intracranial pressure is growth of a tumor that obstructs the duct system of cerebrospinal fluid (CSF), which bathes and nourishes the brain and spinal cord. Common symptoms can include nausea, vomiting, headache that is worse in the morning, and a reduced level of consciousness that causes drowsiness. Tumors causing focal compression on or irritation of the brain usually result in loss of neurologic function. This progressive loss of neurologic function can manifest as tinnitus (ringing in the ears) or aphasia (language problems).

Technical advancement has made surgical removal of brain tumors more effective and safer. Surgical management of intracranial tumors focuses on diagnosis and reduction of tumor mass. Depending on tumor location and patient health status, the neurosurgeon may perform a needle biopsy (called image-directed stereotactic needle biopsy) or a craniotomy to extract a piece of tumor for pathologic analysis. If the tumor is located in an area where surgery can be performed, the neurosurgeon generally will remove the mass if the patient can tolerate general anesthesia. Exceptions to a surgical option may be exercised to treat malignant tumors that are very sensitive to chemotherapy or radiation therapy (i.e., to manage lymphoma or germinoma). One of the most common types of tumors is the glioma, which accounts for 50% of all primary brain tumors.

Degenerative disorders of the spine

Degenerative disorders of the spine are a common problem. Between 50% and 90% of the population will experience back pain at some point in their lifetime. Most of these symptoms subside on their own within a few weeks; the cost, however, is realized in decreased productivity and lost wages—a public health problem. Pain in the lumbar spine is the most common reason adults seek medical attention. The lumbar spine comprises five lumbar vertebra and supports the weight of the entire vertebral column and head. Lower back disorders are among the most frequent reasons for referral to a neurosurgeon. Lumbar discs are prone to herniation and desiccation (drying out) as a result of the heavy load they bear and the motion to which they are subject. Nerves that run from the vertebrae extend out to distant body parts, and degeneration of the discs may change bony structures in such a manner that can cause nerve compression. Typically, patients with degenerative disorders of the spine may experience pain, numbness, paresthesia (tingling), and restriction of neck movement (if the affected vertebra is in the cervical spine, which is located in the back of the neck).

Surgery for congenital abnormalities

Congenital abnormalities arise during embryonic development. Important changes in growth and chemistry occur during the second week of human gestation; these changes contribute to the development of the nervous system. Several different types of cells proliferate as they move together or separate into other structures according to an orchestrated, natural timeline. Defects can occur at different stages of development. Among the defects with which infants can be born include myelomeningoceles, encephaloceles, hydrocephalus, and craniosynostosis.

Central nervous system infections

Solitary or multiple brain abscesses can occur as a result of infection in the brain. Patients present with clinical symptoms such as focal (a specific area is affected) neurologic signs, seizures, altered mental status, and increased intracranial pressure. CT scans and magnetic resonance imaging (MRI) are helpful for identification of brain abscesses. Surgery is usually indicated if the abscess fails to resolve or worsens following antibiotic treatment, or if there are signs of mass effect and brain herniation. Although rare, a spinal epidural abscess can occur. Typically, bacteria can spread in patients who have acute bacterial meningitis (infection of the subarachnoid spaces and meninges). The specific type of bacteria varies according to the patient’s age.

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

A neurosurgeon performs the procedure in a major hospital. The neurosurgeon is a medical doctor who has obtained two years of general surgery training, plus an additional five years of training in neurosurgery.

Functional neurosurgery

Functional neurosurgery is a special type of surgical procedure used to manage movement disorder, epilepsy, and pain. Stereotactic neurosurgery makes use of a coordinate system that provides accurate navigation to a specific point or region in the brain. This is usually done by placing and fixing into position a frame on the scalp (using four threaded pins that penetrate the outer skull to stabilize the frame in position) under local anesthesia. A special box and ster-otactic arc are placed to precisely determine X, Y, and Z coordinates of any point within the frame.

Epilepsy surgery

Approximately 70 per 100,000 population in the United States takes antiepileptic medications for seizure disorders. The risk of developing epilepsy over a lifetime is 3%, and there are 100,000 new cases per year. The majority of cases (approximately 60,000) are epilepsy of the temporal lobe (the brain lobes located on the sides of the head). Approximately 25% of temporal lobe seizure patients who are prescribed anti-epileptic drugs continue to have seizures that are not controlled or that can be controlled, but the side effects of the medication outweigh the therapeutic benefits. Approximately 5,000 new cases per year require epilepsy surgery (partial anterior temporal lobectomy ). The patient and neurosurgeon should consider surgery if continued seizures cause injuries due to repeated falls; driving restrictions; limitation of social interactions; problems related to education and learning; and employment limitations.

The future of neurosurgery

Neurosurgery as a field is faced with many new opportunities and challenges, based on advanced technological approaches and molecular approaches to neurosurgical problems. Advances in technology have allowed the neurosurgeon to precisely locate abnormal tissue in the brain and spinal cord, thereby preserving

QUESTIONS TO ASK THE DOCTOR

  • What the potential side effects that can arise as a result of surgery?
  • How likely are complications to develop?
  • How long will recovery take?
  • Will I undergo rehabilitation, and if so, for how long?

normal tissues from surgical trauma. In addition to cardiovascular neurosurgery, functional neurosurgery, neuro-oncologic neurosurgery (surgical removal of brain tumors), and spinal surgery, the future holds many new research innovations. In the new millennium, the field of molecular neurosurgery can make it possible to introduce genetic material into nerve cells and to redirect protein synthesis—to work toward reversing the disease process, in general.

Resources

BOOKS

Goetz, CG. Goetz’s Textbook of Clinical Neurology. 3rd ed. Philadelphia: Saunders, 2007.

Khatri, VP and JA Asensio. Operative Surgery Manual. 1st ed. Philadelphia: Saunders, 2003.

Townsend, CM et al. Sabiston Textbook of Surgery. 17th ed. Philadelphia: Saunders, 2004.

PERIODICALS

Freese, A., Simeone, F. “Ocular Surgery for the New Millennium.” and “Treatment of Neurosurgical Disease in the New Millennium.” Ophthalmology Clinics of North America 12, no. 4 (December 1999).

ORGANIZATIONS

The American Board of Neurological Surgery. 6550 Fannin Street, Suite 2139 Houston, TX 77030. (713) 441-6015. http://www.abns.org.

Laith Farid Gulli, M.D., M.S.

Miguel A. Melgar, M.D., Ph.D

Nicole Mallory, M.S., PA-C

Nissen fundoplication seeGastroesophageal reflux surgery

Nitrite test seeUrinalysis

NMR seeMagnetic resonance imaging

Nonmelanoma skin cancer surgery seeCurettage and electrosurgery

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Neurosurgery

Neurosurgery

Neurosurgery is a medical specialty concerned with the diagnosis and treatment of the central and peripheral nervous system .

The nervous system is composed of the brain , spinal cord and spinal column, as well as the nerves that travel through all parts of the body (hands, legs, arms, face). Neurosurgeons treat degenerative and congenital diseases of the spine, pain from pinched nerves in the neck, lower back pain, sciatica, carpal tunnel syndrome , epilepsy , stroke , Parkinson disease , chronic pain and sports injuries of the head and spine, in addition to brain tumors, hemorrhages and trauma, tumor of the pituitary gland, and disorders of the arteries that carry blood from the heart to the brain. The field of neurosurgery encompasses both adult and pediatric patients. Neurosurgery has one of the longest training periods of any medical specialty due to the extreme complexity of the nervous system and the advanced techniques used in neurosurgical operations.

Neurosurgery may have begun in the early stages of man's evolution . Skulls of early man show signs of incision through the bone. Some skulls have as many as five openings cut into them. Some of this ritual was probably for magical purposes and some was medicinal, performed to release the spirits that were causing excruciating headaches or making an individual show signs of insanity, or to remove bone fragments resulting from trauma. This process is called trephination (less commonly, trepanation) and was a common procedure as early as the Neolithic period. Interestingly, this procedure was done in human settlements around the world. These clans or tribes had no contact with each other, yet they devised and practiced a similar procedure as a form of spiritual or medical therapy.

Trephining was accomplished with a sharpened flint moved in rapid circular motions to cut through the bony skull. The procedure took about a half hour on a drugged patient. It is likely that early man had discovered the means to immobilize an individual so that surgery could be carried out. Trephining was practiced as late as the mid-twentieth century among isolated peoples. Even cadavers were trephined to remove bone fragments, which were then worn as amulets.

Needless to say, the survival rate of trephination was low. However, skulls have been found that show bone growth around the edges of the opening, indicating that the patient survived for a time after the procedure. More often, skulls with trephined openings show the raw, incised edges of the operative area, indicating that the patient probably died during surgery or shortly thereafter. Infection was not understood and was a high probability following surgery in such conditions.

It was not until the late nineteenth century that further progress was made in the field of neurosurgery. In November, 1884, two British surgeons, Bennett and Godlee, operated to remove a brain tumor. Shortly thereafter, in 1888, Sir Victor Horsley removed a tumor from the spinal cord of one of his patients. That same year an American surgeon, W.W. Keen of Philadelphia, removed a meningioma, a hard, slow-growing tumor that grows on one of the membranes covering the brain. In 1889, Keen tapped the ventricles of the brain, the small openings at the base of the brain where fluid collects.

The development of the x ray provided a means for neurosurgeons to find tumors growing in the brain, bone splinters, or other foreign objects. Still, it remained difficult to locate these growths precisely enough for surgical removal. The invention of stereotactic frames to provide precise guidance to underlying tumors helped revolutionize surgery on the brain.


Application of neurosurgery

Current neurosurgery includes trephination along with other procedures to correct not only injury and disease of the central nervous system, but also to modify nerve supply to other areas of the body that may benefit from such surgery and to enhance blood supply to the brain. A number of conditions are commonly treated by neurosurgery. Injuries of the skull, brain, vertebral column and spinal cord are common diagnoses in neurosurgery and are most commonly caused by motor vehicle accidents or sports accidents.

Injury to the head or spinal column may result in swelling of the enclosed nervous tissues, bleeding inside the skull that would place pressure on a localized area of the brain, or may involve bone fragments impinging on the brain or spinal cord as a result of a blow to the head or back. Certain congenital conditions such as hydrocephalus (excessive fluid on the brain) or spina bifida (a condition in which the spine has not closed around the spinal cord) frequently are treated by the neurosurgeon. Premature closure of the skull, which will prevent the skull from expanding as the brain grows, also requires surgery to separate the skull bones.

Tumor growth in the skull or spinal column may also require surgical correction. A benign (noncancerous) tumor in the brain is usually well defined and can be removed by delicate surgery. A malignant (cancerous) tumor presents a much more challenging problem because it is not defined as clearly or contained as well as the benign growth. Still, some areas of the brain remain unreachable by surgical tools and a growth in those areas cannot be removed. In that case, the physician may resort to radiation therapy or the use of antitumor drugs.

The brain requires an especially copious blood supply. Large arteries in the side and back of the neck carry blood to the brain, but when these arteries become narrowed or blocked by fatty deposits (a condition called atherosclerosis), the blood supply to the brain may be reduced to an insufficient amount. A balloon catheter may be used by the physician to clear the blockage. In this procedure, called angiography , a catheter is guided to the site of blockage. The tiny balloon on the end of the catheter is inflated to press the blockage out of the way. The balloon is then deflated, and the catheter removed. In the event this procedure is not effective, the surgeon may need to operate on the blood vessels instead of the brain itself. A graft to bypass the blocked area may be called for or the vessel may be opened and the deposit removed (a procedure called endarterectomy) if the artery is accessible. In addition, an artery can balloon from the pressure of the blood within it. This is called an aneurism , and it forms at the site of a weak spot in the arterial wall. The swollen artery in itself may do no harm, but the weakened arterial wall can burst at any time, allowing the escape of blood into the brain. This is one form of stroke. If the artery is accessible, the surgeon can remove the weak area and sew the ends of the artery together again. If the artery cannot be reached for surgical correction, some means can be taken to reinforce the arterial wall from within.

A so-called slipped disk or ruptured disk, damage to one of the cartilaginous disks between the vertebrae, may form a protrubance into the spinal canal that impinges on the spinal cord. This may cause pain or even the inability to walk normally. Here again, the neurosurgeon may need to take steps to remove the protrusion and in some cases fuse the vertebrae to prevent their flexing on the weakened disk.

In cases of intractable pain or involuntary movements that cannot be corrected, the surgeon may be called upon to interrupt the nerve supply to a given area. This function is being taken over more and more by medical therapy as physicians learn new information about nerve functions and how to interrupt them medicinally, but the surgeon still provides a needed service.

Locating a tumor or area in which blood has been released inside the skull requires a rigorous diagnostic procedure. If the patient has had an accident such as a fall or automobile wreck in which he struck his head, the surgeon may be more aware of the possibility of the existence of a blood clot forming on the brain, bone fragments that may be impinging on the brain, or swelling of the brain. If the patient denies any accidental trauma to the head, but has had persistent and longstanding headaches, visual disturbances, dizziness, or other lingering symptoms, the surgeon is alerted to the possibility of an aneurism or other source of blood leakage or a developing tumor.


Diagnosis

The diagnosis of the source of a brain disorder has become infinitely more precise with the modern technology of computerized tomography (CT scan) and magnetic resonance imaging (MRI) . Either of these scans shows several views of the brain and the presence of a tumor, excessive fluid build-up, or intracranial bleeding. They also provide the means for precise measurement of the depth of the growth and its angle from various landmarks on the skull. This enables the neurosurgeon to use a stereotactic frame to guide his instruments precisely to the site of the lesion.

The CT or MRI image shows a cross section of the brain at a certain level. Each exposure is slightly advanced from the previous one. In all, the images appear to be slices of the brain that show various details at each level. The computer control also allows the images to be combined to form a three-dimensional image so the physician can see the tumor or damaged area of the brain in relation to the complete structure. In this way he can decide whether the patient is a candidate for surgery or whether the tumor or other lesion is not accessible. The image also gives a good idea of whether the tumor is a cancerous lesion or is benign.

Advances in neurosurgery

Diagnostic accuracy allows the surgeon to work precisely where he or she wants to work with amazing efficiency and reliability, each and every time. The result is that the surgical incision has been reduced to an absolute minimum. Smaller incisions, less tissue trauma, and better surgical planning have reduced the overall risk of brain surgery from almost 90% in the 1940s to about less than 2% in the twenty-first century.

A groundbreaking medical advance of recent years, is the Leksell gamma knife. This revolutionary new treatment is a safe, effective, and cost-efficient alternative to conventional neurosurgery for certain patients. Developed in 1968 by Swedish professors Lars Leksell and Borge Larsson, the Gamma Knife is a highly advanced instrument used to treat arteriovenous malformations (AVM), facial pain, benign and malignant brain tumors, and other functional brain disorders. What makes the gamma knife so unique is that it successfully treats these conditions with no incision. Instead, it uses a concentrated radiation dose from Cobalt-60 sources. A total of 201 beams of radiation intersect to form a powerful tool focused on a targeted area of abnormal tissue within the brain. The gamma knife is so precise that it damages and destroys the unhealthy tissue while sparing adjacent normal, healthy tissue.


Intraoperative guidance systems

Just as the space shuttle is guided in mid-flight, so the hand of the surgeon can be guided in mid-operation. Stereotactic guidance systems (involving surface markers or "frames," computers, etc.), three dimensional computer-assisted guidance systems (via infrared lights, lasers, mechanical arms, radiotelemetry), even real-time imaging such as intraoperative ultrasonic guidance systems and MRI, and finally computer guided mechanical arms (hands free) are all available to today's surgeon.

Stereotactic surgery is the use of a special frame that attaches to the skull and serves to guide the surgeon's instruments, electrodes, or cannulae precisely to a local area. The frame is called a stereoencephalotome, which combines the Greek words for solid, head, and to cut; thus, it is an instrument to cut through the solid head. In fact, the stereoencephalotome does no cutting. Instead, it is an instrument with a rounded frame that attaches to the patient's head and can be used to guide instruments at precise angles into the brain.

Once the surgeon has located the area of the brain in which to operate, he places a stereotactic frame on the patient's head. Several types of frame can be used, each of which differs in its type of orientation. Some frames must be oriented with a trephined opening in the skull. Others are oriented using landmarks on the skull such as the ear canals. Once the surgeon has placed the frame over the brain lesion he can position movable arms in the frame to guide electrodes or other instruments into the substance of the brain. Tissue destruction can interrupt pain pathways to reduce pain from cancer or other lesions, which helps the patient better cope with therapy. Certain diseases such as Parkinsonism or hyperkinesis, which involve involuntary movements or shaking can be helped by destroying a small area within the brain. Also, this method can be used to remove a blockage of the drainage system of the brain, which in turn allows the build-up of cerebrospinal fluid and causes hydrocephalus. Removing the tumor blocking the drainage canal or implanting a tube through the canal to drain the fluid relieves the pressure within the skull. Of course, foreign bodies such as bullets also can be located and removed. Precisely focused radiation can be guided by stereoframes to converge on the site of a tumor and destroy it.

As physicians learn more about the brain and the precise location of various functions within it, the use of stereotactic surgery grows. The brain is the only organ that can study itself, and it continues to accumulate knowledge that serves its own best interest in times of illness or injury. With current technology, scientists have begun the implantation of electrodes in the brain to allow the deaf to hear and the blind to see. The electrodes are threaded into the area of the brain that controls hearing or sight and then are connected through a computer to a light or sound receptor. Although this technique is in its early stages, progress in miniaturization of the hardware and the improved knowledge of brain structure and function are combining to make this field a promising venture for the near future.

See also Neuron; Neuroscience.

Resources

books

Kaye, A.H. Brain Tumors. An Encyclopaedic Approach. Churchill Living, 2001.

Jonathan, S., Citow, R., Macdonald, R., Kraig, R. L. Wollmann, L. Comprehensive Neurosurgery Board Review. Thieme Medical Publ., 2000.


periodicals

Ganz, J.C. "Gamma Knife Radiosurgery and its Possible Relationship to malignancy: a Review." J Neurosurg. 2002 Dec: 97(5 Suppl): 644–52.

Levivier M., et al. "The Integration of Metabolic Imaging in Stereotactic Procedures including Radiosurgery: a Review." J Neurosurg.. 2002 Dec; 97(5 Suppl): 542–50.

Snyder, D.P. "Repairing the Mind With Machines: The Super-normal Possibilities of Neural Prosthetics." Omni. 15 (September 1993):14.


Larry Blaser

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cannula (plural: cannulae)

—A hollow tube inserted into an area of the body to drain fluid, guide an instrument, or provide a means to measure pressure or temperature.

Hyperkinesis

—Excessive movement or motor activity. A syndrome that results from a brain lesion and leads to fidgeting, nervousness, constant movement, short attention span, and other symptoms in adolescence.

Neolithic period

—The geological period that began approximately 12,000 years ago. It was during this period that man developed advanced stone tools and began forming farming societies.

Neuro

—Refers to the nervous system, including the brain, spinal cord, or the nerves leading to and from them.

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"Neurosurgery." The Gale Encyclopedia of Science. . Encyclopedia.com. 10 Sep. 2018 <http://www.encyclopedia.com>.

"Neurosurgery." The Gale Encyclopedia of Science. . Encyclopedia.com. (September 10, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/neurosurgery

"Neurosurgery." The Gale Encyclopedia of Science. . Retrieved September 10, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/neurosurgery

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Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
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