Neurosurgery

From Psy3242

Current revision as of 06:56, 29 April 2008

Definition

Neurosurgery is the medical specialty concerned with the prevention, diagnosis, treatment and rehabilitation of disorders that affect the entire nervous system including the spinal column, spinal cord, brain and peripheral nerves. Some of the general categories of neurosurgery include: treating tumors of the CNS, treating seizure and movement disorders, treating the affects of injury to the CNS, treating strokes, and treating chronic pain.SOURCE: The American Association of Neurological Surgeons (AANS).

While all of this is very interesting, the aspects of neurosurgery that bear particular relevence course material include: biopsy, functional neurosurgery, commisurotomy,lobotomy, and hemispherectomy.

Surgical Management of Seizures

Point of interest: While performing surgery on awake patients for the treatment of epilepsy, Wilder Penfield was able to stimulate various parts of the primary somatosensory cortex and ask patients where on their body they felt sensation. Through this practice Penfield was able to map the topographic representation in the primary somatosensory cortex.

Temporal Lobectomy

Temporal lobectomy is the removal of a portion of the temporal lobe of the brain. It is the most common type of epilepsy surgery and is also the most successful type. This procedure is carried out when the seizures clearly arrive from a circumscribed area. H.M underwent a temporal lobectomy and suffered severe amnesia because both his temporal lobes were incapable of carrying out memory tasks. Because surgeons do not want their patients to suffer in the same manner the Wada Test is administered.

Commissurotomies

A commisurotomy is a neurosurgical procedure in which the corpus callosum, the large fiber tract connecting the right and left hemispheres, is split. Millions of axons run from one side of the brain to the other via the corpus collusium. These axons allow the two hemispheres to communicate. After the coomisuratomy the hemispheres can no longer send messages to one another. The procedure did not have a profound effect on evryday psychological functioning, although hemisphere rivalry (for example one hand trying to open a door while the other is trying to close it) occasionally occurs. The commisurotomy was first performed in humans in the 1940s in an attempt to control epilepsy and yielded mixed results; however it is important to note that the corpus callosum was probably not divided completely in most of these first patients. By separating the two hemispheres the hope was that seizures could no longer spread from one hemisphere to the other. Bogden and Vogel were the first neurosurgeons to perform complete commisurotomies, which incuded the dividing of smaller commisures as well as the corpus callosum. Their most prominent patients were: LB, NG, and AA. The collosotomy is a staged commissurotmy in which only the corpus callosum is split and gradually, over two separate surgeries. Michael Gazzaniga was a proponent of the collosotomy.

Hemispherectomy

Is the removal of one cerebral hemisphere of the brain. The usual reason for performing a hemispherectomy is to remove a severely diseased, damaged or atrophied hemisphere. In many cases, this damaged hemisphere causes epileptic seizures preventing the healthier hemisphere from functioning. The hemispherectomy is very successful in treating seizures although the more the patient has learned the lower their IQ will drop after the surgery (so adults suffer extensive cognitive deficits from the surgery and children do not). The hemispherectomy is almost exclusively performed on children, because their brains exhibit a high level of plasticity which enables the remaining hemisphere to take over the responsibilities of the hemisphere removed. Kate, a patient described in “Fractured Minds” demonstrated that children who have undergone a hemispherectomy can lead relatively normal lives.

Pschosurgery

Lobotomy

is a type of brain surgery that is conducted in an effort to decrease a person’s psychiatric symptoms. In the 1930’s and 1940’s frontal lobotomies in which the frontal lobes were completely removed or severed from the rest of the brain were relatively common treatments for psychiatric disorders. Once it became apparent that the side effects of the operation (mental inertia, loss of personality, and relapse) greatly outweighed the surgery’s benefits, the lobotomy fell out of favor and with the advent of drug therapy ceased to be carried out almost entirely. 

Psychosurgery Today A Leucotomy is a procedure in which the frontal lobes are partially disconnected from the rest of the cortex by sectioning the thalamofrontal fibers in the lower medial quadrant of the frontal lobe. This procedure is rarely used, and only as a last resort, for patients suffering from psychiatric symptoms, specifically those related to Obsessive Compulsive Disorder. Unlike the lobotomies carried out in the 1930’s and 1940’s the leucotomy is reported to produce minimal frontal lobe symptoms.

Tumors

Craniotomy

In removing a brain tumor the surgeon performs a craniotomy (removing part of the patients skull called the "scull flap"), to insure that he or she can fully access the tumor and remove as much of it as possible. The goal is to remove the tumor, while harming as little brain matter as possible, and not harming the patients speech, movement, and memory capabilities.

Biopsy

Often times before a craniotomy a sterotactic biopsy is done. This is so the neurosurgeon can make sure that the tumor is malignant. A small hole is drilled so a small sample of tissue can be removed.

Intraoperative language mapping

Intraoperative language mapping is a technique used for patients with tumors affecting language function. This procedure involves operating on an awake patient and mapping the anatomy of their language function during the operation, prior to deciding which portions of the tumor are safe to resect.