Neurosurgery is a specialized field of surgery for the treatment of diseases or conditions of the central nervous system (CNS) and spine.
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: 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.
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 types—subarachnoid 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 (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 (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 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 wages—a 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).
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.
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 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.
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.
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 synthesis—to work toward reversing the disease process, in general.
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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
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.