affects some 2.7 million Americans—more than Parkinson’s disease
, multiple sclerosis
and amyotrophic lateral sclerosis
(Lou Gehrig's disease) combined. More than half of patients can achieve seizure control with treatment, yet almost a third of people with epilepsy have a refractory form of the disease that does not respond well to existing antiepileptic drugs. Nor are these patients typically helped by the one implanted device—Cyberonics' Vagus Nerve Stimulator (VNS)
—that has had U.S. Food and Drug Administration approval for treatment of epilepsy since 1997.