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Wearable Devices and EEG Under the Scalp Predict Seizures with Near-Perfect Accuracy

​A wearable watch and a subcutaneous EEG device placed under the scalp independently and accurately forecast seizures about two-thirds of the time in patients with epilepsy, according to findings reported in April at the AAN Annual Meeting in Boston.

“The unpredictability of seizures is the most difficult aspect of epilepsy," said the principal investigator, Benjamin H. Brinkmann, PhD, an engineer, professor of neurology, and clinical support scientist for the division of epilepsy at Mayo Clinic in Rochester, MN. “If a person with epilepsy doesn't know when a seizure will happen, they must conduct themselves as if it will happen anytime."

Implantable devices tested in research studies also can warn someone that they are at higher risk for a seizure, but it can be a hard sell to add recording devices to the brain, Dr. Brinkmann said.

Mayo Clinic scientists collaborated with researchers at King's College London and the University of Melbourne to recruit and test the devices in 39 patients with epilepsy and one healthy volunteer. Participants wore the devices for eight months or longer—the equivalent of 16,000 days.

Each center used different wearable watches and an EEG brain-monitoring device. The investigators analyzed data from 1,700 seizures to identify circadian and multi-day cycles to determine whether certain patterns could forecast and detect seizures.

The investigators accurately identified a high-risk period when a seizure was more likely to occur about two-thirds of the time, which is a lot better than chance, Dr. Brinkmann said. The more scientists understand about seizure forecasting, the better they can predict the high-risk days, he added.

“We think there is a seizure-permissive brain state where patients are more likely to have a seizure," Dr. Brinkmann said.

The somewhat bulky wearable watch in this study captured heart rate, blood flow, and skin conductance, and the scalp EEG identified long-term electrical brain activity patterns that set the stage for a seizure. They also used smartphone apps that let patients log their seizures so the brain patterns on the EEG could be linked to the time and date of the event.

The Mayo team also received funding from the National Institutes of Health (NIH) to determine whether they could pair seizure forecasting on high-risk days with a benzodiazepine to see if it reduced seizure activity.

“This is the best research money can buy," said Jacqueline A. French, MD, FAAN, professor of neurology at the NYU Comprehensive Epilepsy Center and chief medical and innovation officer for the Epilepsy Foundation, which funded the study. “This type of forecasting could allow people to live with less worry."

Dr. French added that the benefits could potentially affect medication regimens. For example, she asked, “What if seizure forecasting got really good and allowed patients to take medication only when they were at high risk for a seizure? Conversely, what if they were taking a lower dose and could increase it on days when the risk is higher?"               

“We now know that seizures are less random than we once thought," said Vikram Rao, MD, PhD, associate professor of clinical neurology and chief of the epilepsy division at University of California, San Francisco. Implantable recording devices have opened the door to the idea that it is possible to forecast seizures based on cycles in brain activity that presage a seizure.

“The dream is to develop non-invasive forecasting systems so all people living with epilepsy can benefit," he said. “This study demonstrates that wearable sensors and EEGs that are placed right under the scalp outside of the skull can have forecasting value. A lot of patients will be interested in these devices and forecasting methods that address the uncertainty of not knowing when their next seizure will come."

Dr. Rao said more work needs to be done to ensure forecasting is as accurate as possible. Researchers also want to determine how patients wish to receive the seizure forecasts and what forecasting horizon is optimal.

“We also need to understand what it means to give someone forecasting information," Dr. Rao said. “Does it change their behavior? What if they have a seizure on a low-risk day? Or, what if they are told that it is a high-risk day, and they change their plans and don't have a seizure? We have never been able to do this type of forecasting, so there is a lot we need to learn."

Dr. Brinkmann has received consulting fees from Otsuka Pharmaceuticals, has stock in Cadence Neuroscience, has received intellectual property interests from a discovery or technology relating to health care, and has a non-compensated relationship as a co-investigator with Medtronic Inc. that is relevant to AAN interests or activities. Dr. Brinkmann's institution has received research support from the Epilepsy Foundation of America and the NIH. 

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