Epilepsy - Surgery

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• A battery-powered device similar to a pacemaker is implanted under the skin in the upper left of the chest.
• A lead is then attached to the left vagus nerve in the lower part of the neck.
• The neurologist programs the device to deliver mild electrical stimulation to the vagus nerve. (Patients may also pass a magnet over the device to give it an extra dose if they sense a seizure coming on. This appears to help about 25 - 30% of patients.)
• The batteries wear out after 3 - 5 years and need to be removed and replaced by a simple surgical procedure.

An investigational approach called deep brain stimulation (DBS) targets the thalamus, the part of the brain that produces most epileptic seizures. Early results have been promising. Researchers are also studying other implanted brain and nerve stimulation devices such as the responsive neurostimulator system (RNS), which detects seizures and stops them by sending electrical stimulation to the brain. A third investigational approach, trigeminal nerve stimulation (TNS), stimulates a nerve involved in inhibiting seizures.

Candidates. The American Academy of Neurology recommends VNS for:

• Patients who are over 12 years old, and
• Have partial seizures that do not respond to medication, and
• Are not appropriate candidates for surgery

Evidence is accumulating, however, to indicate that VNS is effective and safe for many patients of all ages and for refractory epilepsy of many types.

Success Rates. Studies are reporting that the procedure reduces seizures within 4 months by up to 50% and even more in many patients. Studies report that it has been effective for longer than 7 years. In one study that followed patients for a year, the benefits of VNS appeared to increase over time.

Complications. Vagus nerve stimulation does not eliminate seizures in most patients and is still somewhat invasive. VNS can cause shortness of breath, hoarseness, sore throat, coughing, ear and throat pain, or nausea and vomiting. These side effects can be reduced or eliminated by reducing the intensity of stimulation. Some studies suggest that the treatment causes adverse changes in breathing during sleep and may cause lung function deterioration in people with existing lung disease. People who have obstructive sleep apnea also should be cautious about this procedure. Turning off the VNS (for example before an MRI or surgery) may increase the risk for status epilepticus. (However, VNS may also be helpful for treating status epilepticus in some patients.)

Experimental Procedures

Gamma Knife Surgery. A device called a gamma knife delivers very focused beams of radiation. Typically used for brain tumors, it is now under investigation for temporal lobe epilepsy and for seizures due to cavernous malformations.

Review Date: 11/15/2006
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital