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Catching Seizures Before They Occur

by Michael Johns, Project Manager | July 07, 2006
As reported in Technology Review, an MIT Enterprise

Researchers at MIT and Harvard are preparing to carry out trials of a new device for treating epilepsy. If successful, it would be the first such device to automatically detect and treat seizures, says John Guttag, at MIT's Computer Science and Artificial Intelligence Lab, who developed it with colleague Ali Shoeb and Steven Schachter, a neurologist at Harvard Medical School, in Boston.

Currently, more than two million people in the United States alone have epilepsy. And globally it affects one in every 100 people. While about half of them are able to treat the condition with drug therapies, many others fight a constant battle to find the right drugs to target their condition. And, for many sufferers, such as those whose epilepsy is caused by trauma to the brain, drugs are not an option.

Guttag is working on a technological alternative that involves implanting a pacemaker-like device in the patient's chest. Connected to the device is an electrode that wraps around the vagus nerve, a large nerve that runs down from the brainstem through the neck and into the abdomen. This vagal nerve stimulator (VNS) has two modes, says Guttag. One stimulates the nerve electrically at regular intervals. "There is some evidence that this periodic stimulation has a long-term prophylactic effect," he says. But this is hit or miss.

The other "on-demand" mode, which uses more powerful electrical stimulations, can be activated by the patient when a seizure occurs to try to stop it. Although precisely why this works is unknown, there's plenty of evidence that VNS can actually stop seizures, says Guttag.

But there's a catch. To activate the on-demand mode, patients must swipe a magnetic wrist strap across their chest whenever they feel a seizure coming on, explains Harvard's Schachter. Hence, a patient must be able to sense the early signs of a seizure in enough time to do anything about it.

"In my experiences more than half cannot perceive the onset of the seizures," says Schachter. And of those who do manage to use the magnet, only one in four cases results in a reduction of the seizure's severity, he says. This may be due to a latency effect: any delay could be less effective at reducing the symptoms.

"Part of the problem with VNS is that it's not a closed loop system," says Steven Rothman, a neurologist at Washington University in St. Louis, MO, meaning there's no feedback to the device. He points out that it would be more effective if the system itself, not the patient, could detect the seizure.

For the original story, visit www.technologyreview.com