Device's Mechanism of Action Characterized in Emory PET Studies

August 15, 1997

Media Contacts: Sarah Goodwin, 404/727-3366 - sgoodwi@emory.edu
Kathi Ovnic, 404/727-9371 - covnic@emory.edu

Electrical stimulation of a nerve in the neck can reduce or eliminate seizures by indirectly changing activity in certain brain regions, according to Emory University researchers who were first to clarify how the vagus nerve stimulation (VNS) device recently approved by the Food and Drug Administration (FDA) works in patients with epilepsy.

Clinical trials performed over many year in human patients showed significantly improved seizure control, but the means by which VNS affected seizures remained unclear.

Principal investigator of the only site in Georgia, epileptologist Thomas R. Henry, M.D., and his colleagues at Emory Epilepsy Center, carefully evaluated patients using positron emission tomography (PET) and other means before and after outpatient surgical implantation of the devices by Roy A.E. Bakay, M.D., professor of neurosurgery.

"The PET images showed clearly that applying VNS to the left vagus nerve caused a combination of increases and decreases in blood flow in the right and left sides of the brain's limbic system," says Dr. Henry, who also is associate professor of Neurology, Emory University School of Medicine. "Abnormal function of the limbic system is critical in starting and spreading most partial-onset seizures."

As with a cardiac pacemaker, the pulse generator of the VNS is implanted under the skin in the patient's chest. A lead wire is then routed to the lower neck and attached to the vagus nerve. And similarly to a cardiac pacemaker, a physician (in this case, a neurologist) programs externally how often the generator will send regular electrical pulses (to the vagus nerve). If a patient suspects seizure onset, the system may be self activated by passing a magnet over the chest.

Since the first human implantation the Cyberonics system in 1988, more than 1,000 patients in 24 countries have accumulated more than 2,000 patient-years of data on VNS, according to the company.

Dr. Henry reports that among the Emory patients who participated in the clinical trials, most have been able to reduce the frequency of seizures and some have completely eliminated them.

"VNS itself represents a new era in epilepsy treatment," says Dr. Henry. "It is the first FDA-approved epilepsy treatment that involves electrical stimulation of the nervous system. Previously, standard treatment included only medication or surgery to remove abnormal parts of the brain. Thus, a new line of treatment is available to the approximately 25 percent of epilepsy patients (more than 500,000 Americans) who never attain seizure control despite exhaustive medication treatments and who are not candidates for available forms of brain surgery."

On July 16, the FDA granted Cyberonics Inc. approval to market its implantable vagus nerve stimulation device for partial onset seizures. The NeuroCybernetic Prosthesis Systemå is the first device approved to treat epilepsy.

The device is approved for patients with partial onset seizures that have not been successfully controlled by either antiepileptic drugs or surgery. Partial onset seizures are localized to one portion of the brain, usually the temporal lobe. Grand mal seizures affect most of the brain.

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