An Electronic Victory Against Epilepsy
The vagus-nerve stimulator cuts down on seizures—but no one knows why
Dr. Jacob Zabara , a neurophysiologist at Temple University, was attending a childbirth class with his wife in 1971 when he had an idea that led to an implantable electronic device for preventing epileptic seizures. He realized that if the controlled breathing his wife was learning really decreased pain during birth, the common understanding of the vagus nerve must be wrong. The vagus nerve, the longest and largest in the body, was thought to work in only one direction, carrying information from the brain down to the lungs, heart, and digestive tract. Zabara saw that signals must travel both ways.
With that in mind, he developed a simple setup to show with lab animals that sending an electrical impulse to the nerve would cause it to send a signal to the brain. He then built on earlier research showing that for reasons not understood, electrical pulses to the brain can control seizures. He used drugs to induce seizures in rats and dogs, applied his rudimentary stimulator, and the seizures decreased.
Other doctors soon followed with tests on cats and monkeys. Then Zabara found a partner, Reese Terry, with whom he started a company, Cyberonics. But when the two called on university medical centers to interest them in their research, they were politely turned away. No one wanted to pursue a technology not knowing why it worked.
A turning point came when the late J. Kiffin Penry, one of the nation’s leading epileptologists, agreed to conduct the first clinical tests on humans. Other neurologists were highly skeptical of Penry’s decision, but according to his assistant, Dr. J. Christine Dean, “he was always interested in anything that might work for epilepsy.”
The treatment involved implanting a cookie-sized device below the left collarbone, with positive and negative leads threaded up to the vagal nerve, around which were wrapped two platinum-foil coils. The two leads essentially created a closed circuit among battery, wires, and nerve, thereby concentrating the current on the nerve better than a single lead and decreasing side effects. Penry used a computer to specify the frequency, strength, and duration of the stimulations based on experience and the characteristics of the individual case.
The first implant was performed in November 1988, and a patient named Tony Kincaid was an early success. He had averaged about 80 seizures a day and hadn’t been beyond his yard in five years except to visit Penry. Over nine months beginning in March 1989, Penry slowly increased the strength of the stimulation he gave Kincaid. July 31,1989, was the first seizure-free day Kincaid could remember, and in January 1990 he had his last seizure.
Scientists still don’t understand how the stimulation, which is usually given every few minutes around the clock, works. One theory is that regular pulses somehow cause the brain to ignore the random electrical signals that trigger seizures. Another is that the stimulation makes the brain alter its production of certain chemicals, increasing inhibitory neurotransmitters and decreasing stimulatory ones; these are in effect what the brain uses to communicate with itself.
About three-quarters of the 2.4 million epilepsy cases in the United States are controlled by medication. For the 300,000 sufferers who cannot successfully be either medicated or operated on, the vagus-nerve stimulator offered the first new hope in a hundred years. Cyberonics hopes to get FDA approval to use the device against depression and is researching its use against Parkinson’s and Alzheimer’s diseases, obesity, migraine, and other disorders. Dr. Penry didn’t live to see the stimulator gain FDA approval; he died in 1996, a year before one of the fastest fast-track licensings ever for a medical implant.