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EMBARGOED FOR RELEASE UNTIL 3:00 PM, TUESDAY, APRIL 28, 1998
Long-Term Nerve Stimulation Reduces Epileptic Seizures Epilepsy patients with an implanted device that electrically stimulates the left vagus nerve in the neck continue to have fewer seizures after three years with few side effects, according to a study released during the American Academy of NeurologyÃs 50th Anniversary Annual Meeting, April 25 - May 2, in Minneapolis, MN.
George Morris, MD, study co-author and a neurologist at the Medical College of Wisconsin in Milwaukee, said, "We examined the long-term progress of the patients, including the effect vagus nerve stimulation had on seizure frequency and whether or not that positive effect would be sustained over time. We found evidence of continued seizure reduction and few side effects, most of which diminished over time."
The study followed 253 epilepsy patients who received the implants between 1988 and 1995. After one year, 95 percent of the patients in the study continued receiving stimulation. At two years, 82 percent were still involved in the study and 69 percent after three years. Reduction in seizure frequency improved from 31 percent at one year, to 41 percent at two years and 40 percent at three years.
The impulse generator implanted in the patientÃs chest stimulates the left vagus nerve in the neck for 30 seconds at five-minute intervals, 24 hours per day. The vagus nerve is the main thoroughfare for communication between the brain and major internal organs.
"Appropriate adjustments in the stimulation intervals must to be made for each patient to optimize the benefit," said Morris. "By the second year the dose may be more accurate, which may account for the improvements in seizure reduction reported during the second and third years. Another explanation is that this therapy works through a long-term modification of seizure pathways, and that it takes time to affect."
Morris said patient continuation rates were high, in part because less than 10 percent reported adverse effects. Side effects reported included hoarseness, headache and shortness of breath, all of which decreased in frequency by the third year. Researchers also noted that twice as many patients decreased their seizure medication over the three years as those who increased it.
"Vagus nerve stimulation is a viable and safe, long-term alternative for some epilepsy patients," said Morris. "The stimulation does not interact with other epilepsy medications, allowing patients to continue other therapies."
Vagus nerve stimulation was approved for use in epilepsy patients in the United States in August 1996. Epilepsy, a brain dysfunction typically manifested by attacks of altered awareness or convulsive seizures, is estimated to affect more than two million Americans.
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