New Device Controls Some Seizures
An implantable medical device that sends an electrical jolt to the brain--much the way a pacemaker controls the heart--offers relief for a small number of people with difficult-to-treat epilepsy.
“The device provides new hope for these patients in terms of seizure control and improved quality of life,” said Eli M. Mizrahi, associate professor of neurology and pediatrics at Baylor College of Medicine in Houston and chairman of the Epilepsy Foundation of America’s professional advisory board.
About 2.5 million Americans suffer from epilepsy, a chronic neurological disease that causes seizures--brief interruptions in the normal electrical functions of the brain. Seizures can be as simple as staring off into space or severe enough to wrack the body with uncontrollable movements.
Medications control symptoms in about two-thirds of people with epilepsy. But for the remaining patients, anti-epileptic drugs either fail to work or are accompanied by such severe side effects, including drowsiness and poor concentration, that their use is very limited.
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The new treatment--called vagus nerve stimulation therapy--was approved in July by the Food and Drug Administration for epileptic seizures that begin in one part of the brain and may remain there or spread to the entire brain, as happens in a grand-mal seizure. It is not approved for the type of epilepsy that produces smaller seizures called petit mal. The device, which is manufactured by Cyberonics of Webster, Texas, has been implanted in about 300 patients since it was approved. Last week, Blue Cross/Blue Shield announced it had evaluated the device and found that it met the requirements for coverage. It is up to individual plans, however, to decide whether to pay for the device, which runs about $15,000.
The new treatment involves surgically inserting the device--about the size of a pocket watch--just beneath the skin in the chest. Surgeons then thread tiny plastic electrical leads up the left side of the neck, wrapping them around a branch of the vagus nerve. The nerve stretches from the brain to the heart and abdomen and controls such functions as swallowing, heart rate and taste.
Vagus nerve stimulation therapy “is not a miracle cure,” said Douglas Labar, who directs New York Hospital’s Comprehensive Epilepsy Center. “But it is a different approach that provides some rewarding benefits for some patients.”
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Studies show that about a third of the patients who get the device see their number of seizures cut in half. “That means that some people get fabulous improvement and actually become free of seizures, and some people have no improvement,” Labar said.
Introduced in 1988 by neurophysiologist Jacob Zabara and his colleagues at Temple University in Philadelphia, the device sends a 30-second signal to the brain every five minutes. Its development grew out of the observation that squeezing a limb can halt a seizure in some people with epilepsy, presumably because it sends a signal to the brain that interrupts the seizure. Zabara theorized that electrical stimulation of the vagus nerve might produce the same effect and tried it first in animal experiments.
Exactly why the device works is not understood. A number of researchers have shown that vagus nerve stimulation therapy can prevent seizures in some people and shorten their duration in others. A recent study by a team of researchers from the Veterans Administration Medical Center in Westwood and Emory University in Atlanta found that the treatment increased blood flow to certain areas of the brain that control seizures. Dean K. Naritoku of Southern Illinois University reported preliminary evidence that the device may reduce metabolic activity of certain parts of the brain, which could stop seizures.
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Doctors also can’t tell why some patients are helped by the device while others are not. For this reason, “we select patients very carefully,” said neurologist Bennett Lavenstein.
The leading candidates for the device are people whose seizures are not controlled by standard medications and those who have undergone brain surgery to remove damaged tissue and still not found relief. “It certainly would not be a first-line choice of treatment for patients with newly diagnosed epilepsy, and it may not be the first choice for patients who are good epilepsy surgery candidates,” Mizrahi said.
Studies show that it often takes time for patients to adjust to the device. It may take up to a year and a half to see the full effects of the therapy. As part of long-term safety and efficacy monitoring, David Labiner and his colleagues at the University of Arizona studied 238 patients and found that patients can continue to improve as much as 18 months after the device is inserted.
Those who do not see improvement after 18 months often have the device removed. “Most people leave it in for a pretty good amount of time, hoping that it will help later,” said Labar, who has implanted nearly four dozen devices. Even when vagus nerve stimulation therapy works, it does not eliminate the need for anti-epileptic drugs. The treatment “is not strong enough to work by itself,” Labar said.
