Implantable Devices Could Detect and Halt Epileptic Seizures

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http://www.scientificamerican.com/article.cfm?id=implant-epilepsy-seizure


STIMULATING: A new generation of implantable "closed-loop" devices are designed to monitor the seizure focus, detect patterns of electrical activity that indicate a seizure is beginning, and quickly respond without external intervention.
Image: Courtesy of Henrik Jonsson, via iStockphoto.com

Epilepsy 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.

Because epilepsy causes repeated, sudden seizures, people with the condition would benefit greatly from a therapy that can detect seizures just as they are starting or, eventually, predict them before they begin and prevent them from happening. A new generation of implantable devices is looking to pick up where medications—and even the VNS—often leave off, at least for people whose seizures routinely begin in one part of the brain (the seizure focus). "Closed-loop" devices are designed to monitor the seizure focus, detect patterns of electrical activity that indicate a seizure is beginning, and quickly respond without external intervention. Such responses could include electrical stimulation, cooling or focused drug delivery—all meant to interrupt the activity and stop the seizure.

Closed-loop devices are considered a new frontier in epilepsy treatment because of their responsiveness. By comparison, the VNS is an open-loop device that stimulates the vagus nerve—a pair of nerves running from the brain stem to the abdomen—to deliver mild electrical pulses (which mitigate the electrical activity of seizures) to the brain on a consistent schedule rather than in response to detected seizure activity. The concept of a closed-loop device for epilepsy comes out of the cardiac world, jumping off from implanted defibrillators that monitor the heart and deliver stimulation in response to an event.