January 16, 1998

New device helps ease epileptic seizures

New device helps ease epileptic seizures

A new implantable electrical nerve stimulator available at Vanderbilt University Medical Center is helping to reduce the number and severity of epileptic seizures in patients with a particularly hard-to-treat form of the disorder.

The vagus nerve stimulation (VNS) device works by electronically stimulating the vagus nerve, which carries impulses from parts of the body to the brain and between the brain and internal organs, effectively halting seizures before they begin.

"The VNS device is a palliative treatment option that reduces seizures by 50 percent in one-third of the patients in which it has been implanted," said Dr. Bassel Abou-Khalil, associate professor of Neurology.

VUMC is the only medical center in the region currently using the VNS device, Khalil said.

Unlike many anti-seizure medications, the VNS device actually increases in effectiveness over time, eventually reducing seizures in about half of patients. But even though the VNS device can reduce the number of seizures, it does not eliminate them completely.

"An important thing to stress is that this is a treatment option for patients who do not respond to anti-seizure medication and who are not good candidates for surgery," said Abou-Khalil.

The best candidates for the VNS device are those who have what are called partial-onset seizures, often the hardest type of seizures to control.

This form of epilepsy can be treated surgically if the focal point of the seizures can be isolated and traced to a single area of the brain. However, in some patients the seizure focus can't be localized or there may be more than one seizure focus area.

The VNS device is used only when these other treatment options have been ruled out as too dangerous or ineffective.

Although it is unknown exactly how the signal stimulates the brain, this method has proven effective in reducing the number and frequency of seizures in many patients.

The VNS device, roughly the size of the a small pocket watch, is implanted in the patient's chest, with small wires leading to the left vagus nerve in the neck.

"The left vagus nerve was chosen because it has less input to the heart. There was a concern that the right vagus nerve might affect heart rate," said Abou-Khalil.

Once implanted, the device stimulates the vagus nerve for thirty seconds and then stays off for five minutes so that the nerve isn't damaged. The frequency and intensity of the electrical stimulation can be controlled by the physician using a "remote control" device that is held over the patient's chest.

This "remote control" can be used to adjust the dosage levels that the device sends to the vagus nerve. Physicians can also collect data from the implant about the current settings of the stimulator.

Additionally, the patients themselves are able to activate the device when they feel a seizure coming on by passing a magnet over their chests.

"This new device will offer people who previously did not have any treatment options one which can drastically reduce the number of seizures they have," said Abou-Khalil.