Pallidotomy

Definition

Pallidotomy is the destruction of a small portion of the brain within the globus pallidus internus, or GPi. The GPi helps control voluntary movements.

Purpose

Pallidotomy is performed to treat the symptoms of Parkinson's disease (PD), which results from the death of cells in a part of the brain that controls movement, called the substantia nigra. Part of the normal function of the substantia nigra is to inhibit overactivity of the GPi, which itself communicates with other portions of the brain in complex control circuits. In PD, the overactivity of the GPi is in part responsible for the slowed movements, tremor, and rigidity that are the classic symptoms of the disease. By destroying part of the GPi, some balance is restored to these movement-control circuits, allowing faster and more fluid movements.

Early on in PD, symptoms can be effectively treated with medication, especially levodopa and the dopamine agonists (drugs that act like levodopa). As the disease progresses, increasing amounts of drugs are needed to control symptoms, and the patient's response to the drugs declines. Typically, within 10 years of starting treatment, the patient will develop uncontrolled movements, called dyskinesias, in response to drug treatment. At this point, surgery is considered an option.

The GPi has two halves, which control movements on opposites sides of the body: right controls left, left controls right. Unilateral (one-sided) pallidotomy may be used if symptoms are markedly worse on one side or the other, or if the risks from bilateral (two-sided) pallidotomy are judged to be too great.

Precautions

Pallidotomy is major surgery on the brain. It may cause excessive bleeding, and care must be taken in patients susceptible to uncontrolled bleeding or who are on anticoagulant therapy.

Description

To destroy tissue in the GPi, a long needle-like probe is inserted deep into the brain, through a hole in the top of the skull. To make sure the probe reaches its target exactly, a rigid "stereotactic frame" is attached to the patient's head. This provides an immobile three-dimensional coordinate system, which can be used both to determine the precise position of the GPi and to track the probe on its way to the target.

A single "burr hole" is made in the top of the skull for a unilateral pallidotomy; two holes are made for a bilateral procedure. General anesthesia is not used for two reasons: first, the brain does not feel any pain; second, the patient must be awake and responsive in order to respond to the neurosurgical team as they monitor the placement of the probe. The GPi is close to the nerve that carries visual information from the eyes to the rear of the brain. Visual abnormalities during probe placement may indicate that it is too close to this region, and thus needs repositioning.

Other procedures may be used to ensure precise placement of the probe, including electrical recording and injection of a contrast dye into the spinal fluid. The electrical recording can cause some minor odd sensations, but is harmless.

When the probe is in the correct position, its tip is heated briefly. This destroys the surrounding tissue in an area about the size of a pearl. If bilateral pallidotomy is being performed, the localizing and lesioning will be repeated on the other side.

Content licensed from:

Author Info: Richard Robinson, The Gale Group Inc., Gale, Detroit, Gale Encyclopedia of Neurological Disorders, 2005

This feature is for informational purposes only and should not be used to replace the care and information received from your healthcare provider. Please consult a healthcare professional with any health concerns you may have.