Sept. 27, 2000 -- A new device implanted in the chest of epilepsy patients -- adults as well as children -- can greatly reduce seizures in some patients, even those who have not responded to anti-epilepsy drugs, according to two separate studies.
The device, called a vagus nerve stimulator, "is as good or better than most existing anti-epileptic drugs," says Christopher DeGiorgio, MD, the lead author of one of the studies. "It's permanent, and the nice thing is that it doesn't cause any medication side effects. It doesn't make patients drowsy or slow down their thinking processes." DeGiorgio is vice-chairman of neurology at the UCLA School of Medicine.
Epilepsy is a brain disorder characterized by sudden, unpredictable, abnormal electrical discharges that produce changes in behavior and bodily functions. The changes can range from a momentary loss of awareness to full body convulsions, also called seizures. The causes of the disease vary; some cases occur due to injuries or chemical disorders, while other forms of the disease are inherited. An estimated 2.5 million Americans suffer from epilepsy.
In many patients, epilepsy can be controlled through the use of one or more anti-epilepsy drugs. Other patients can benefit from surgery to remove the part of the brain that is causing the seizures. But for patients whose epilepsy is not well controlled by drugs and who are not candidates for surgery, the vagus nerve stimulation device offers another possibility for getting seizures under control.
The vagus nerve stimulation device is implanted in the chest and gives off electrical impulses to the vagus nerve. Although the mechanism by which it works is not well understood, it is believed that the device blocks certain brain impulses that direct the body to start a seizure.
In the study by DeGiorgio and colleagues, almost 200 patients had the vagus nerve stimulation devices implanted and then were followed up for one year.
In the study, published in the September issue of Epilepsia, 35% of the patients had over a 50% reduction in their seizures, and 20% of patients had over a 75% reduction.
What was most exciting about the results, says DeGiorgio, is the fact that, unlike many drug treatments that can wear off after a while, the vagus nerve stimulation patients actually seemed to improve over time. He attributes this to two factors. "One is that the device's setting are being adjusted [for the best results] by the doctor, and the second is the cumulative effect of the device," he tells WebMD. "The more the brain 'sees' the device, the greater the effectiveness."
All the patients in DeGiorgio's study were taking one or more anti-epilepsy medications during the trial. That's because even patients with severe epilepsy do derive some benefit from medication, says Martha Morrell, MD, professor of neurology at Columbia University, in New York, and chair of the Epilepsy Foundation. "These patients' seizures are not completely controlled by medication, but if they were not on medicine at all, they would be a lot worse," she tells WebMD. "[Vagus nerve stimulation] should be thought of as an [addition] to medication."
The only major side effect of the vagus nerve stimulation device is hoarseness and throat discomfort, which occurs because the nerve being stimulated also controls certain speech functions. However, this problem can be lessened by having the physician adjust the device so that less current is generated, DeGiorgio says.
Another study, done by Ravish V. Patwardhan, MD, a resident in the division of neurosurgery at the University of Alabama at Birmingham, and colleagues, shows that vagus nerve stimulation is also effective in children. Patwardhan's study involved implanting vagus nerve stimulation devices in 38 children, aged 11 months to 17 years. The researchers found that nearly two-thirds of the children treated with vagus nerve stimulation experienced a 50% or greater reduction in seizures.
One possible reason that children seem to do even better with vagus nerve stimulation than adults is that their brains have not had as much damage as older patients, who have suffered from epilepsy longer. "Patients who keep suffering from seizures have a poorer outcome than if the seizures are stopped," Patwardhan tells WebMD. "One patient had had seizures 15 years before the device was put in. That's probably too long to wait." Patwardhan presented his study in San Antonio, Texas, this week at a meeting of the Congress of Neurological Surgeons.
Gregory Barkley, MD, medical director of the Comprehensive Epilepsy Program at Henry Ford Hospital, in Detroit, cautions that despite the promising results, vagus nerve stimulation is not a cure for epilepsy. "It doesn't get you off of anti-seizure medications and it doesn't stop all seizures," he says. "It's more of a salvage procedure when nothing else works."
Patients diagnosed with epilepsy should first try medications to see if that will keep their epilepsy under control. If medications alone do not work, patients should be evaluated to see if they are good candidates for epilepsy surgery. Only if surgery is ruled out as a possibility should patients and their physicians consider vagus nerve stimulation, Barkley says.