MIT device could prevent epileptic seizures
New treatment builds on an existing therapy
Researchers at the Massachusetts Institute of Technology are developing a device that could detect and prevent epileptic seizures before they become debilitating.
Epilepsy affects about 50 million people worldwide, and while anticonvulsant medications can reduce the frequency of seizures, the drugs are ineffective for as many as one in three patients.
The new treatment builds on an existing treatment for epilepsy, vagus nerve stimulator (VNS), manufactured by Cyberonics Inc, which is often used in patients who do not respond to drugs. A defibrillator typically implanted under the patient's collar bone stimulates the left vagus nerve about every five minutes, which has been shown to help reduce the frequency and severity of seizures in many patients.
The MIT researchers and colleagues at Beth Israel Deaconess Medical Center (BIDMC) seek to improve the treatment by combining it with a detector that measures brain activity to predict when a seizure is about to occur. The new device would sense the oncoming seizure and then activate the VNS, in principle halting the seizure before it becomes manifest.
"Our contribution is the software that decides when to turn the stimulator on," said Prof John Guttag, of MIT’s Department of Electrical Engineering and Computer Science. "Our colleague Dr. Steven Schachter, professor of neurology at Harvard Medical School and epileptologist at BIDMC, suggested hooking our detector up to the VNS," he said. MIT and BIDMC researchers plan to test the new device in epilepsy patients this fall. If it seems effective, more comprehensive trials will be launched.
A look at brain patterns
The detector works by measuring brain activity with electrodes placed on the patient's scalp. In its current form, the patient wears something resembling a bathing cap, in which electrodes are embedded. In order to adapt the detector to work with the VNS, researchers connected wires from the cap to a laptop computer or microprocessor that activates the implanted defibrillator.
Prof Guttag believes the technology could be refined so the electrodes could be worn inside of a headband or baseball cap, making the device less obvious to observers.
Each epilepsy patient has different brain activity patterns, so the detector is programmed to measure an individual's patterns to determine what the precursors to a seizure look like for each patient.
"It's quite tricky to try to detect very early signs of seizures because there are abnormal electrical signals that don't evolve into seizures," Prof Guttag said. "If we can learn what the right profile is for an individual, we can build a seizure onset detector that works really well for that person."
Ideally, when the device senses an impending seizure, it sends a magnetic signal to the implanted stimulator, which in turn activates the left vagus nerve. The vagus nerve sends electrical signals up to the brain as well as down toward the viscera, controlling heart rate, gastrointestinal peristalsis, sweating and keeping the larynx open for breathing. The mechanism by which VNS prevents seizures is not known, but the technique has been FDA approved to treat epilepsy for about 10 years.
About 32,000 epilepsy patients already have VNS implants. Some of them are able to use a handheld magnet to activate the VNS on demand, but many cannot. If the new detection device is successful, it would allow many more patients to use the VNS on demand.
The device could also be adapted to provide warnings for patients who don't need or want VNS implants. Once the device alerts the patient that a seizure is imminent, that person could take steps to minimize injury, such as sitting down or moving away from potentially dangerous objects, such as a hot stove.
Although the seizure detector could have a huge impact on epilepsy patients, there are plenty of other potential applications for technology that analyzes electrical activity in individual brains, Guttag said. Depression, schizophrenia and attention deficit disorder are just a few of the conditions that could be studied.