In order to assess the severity of epileptic seizures, patients are typically required to have electrodes placed on their scalps, which are then wired into an electroencephalograph (EEG) system. Needless to say, this requires them to be at a hospital, and remain there until a seizure occurs. Scientists from MIT, however, have developed what could be a much more user-friendly alternative – a seizure-monitoring wrist sensor that is worn by patients as they go about their day-to-day lives. Not only has it been shown to measure severity as accurately as EEGs, but it could also let patients know when to seek post-seizure medical attention.
The sensor was designed by a team led by Rosalind Picard, a professor of media arts and sciences. Originally, it was intended to identify the emotional state of autistic children, as their behavior is often not a true indicator of their mood. It did this by gauging the state of their sympathetic nervous system, as measured via the electrical conductance of their skin.
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In a study that the team conducted on seizure-prone autistic children at Children’s Hospital Boston, however, it was discovered that the higher a patient’s skin conductance during a seizure, the more time it took for regular brain wave activity to resume afterwards – brain waves are what an EEG measures.
Previous studies have suggested that the longer brain wave activity is suspended, the more likely the occurrence of sudden unexplained death in epilepsy (SUDEP), a condition that can result in death within a period of hours after a seizure. Currently, one of the gauges that patients use to decide whether a particular seizure has put them at risk of SUDEP, is its duration. In the Children’s Hospital study, however, the team found that severity didn’t necessarily have anything to do with duration – and they believe that severity is what determines how long the brain waves stop.
By using skin conductance to measure the severity of seizures instead of just their duration, the wrist sensors could provide a more accurate way of letting patients know if they need to seek medical attention after a seizure. Picard also noted that pronounced spikes in conductance sometimes preceded seizures, which caused her to wonder if the sensors could also be used to warn patients when a seizure is about to occur.
In a subsequent study, the team proceeded to incorporate the sensors into unobtrusive wrist sweatbands which were worn by severely epileptic children spending up to a week at the hospital, being monitored by EEG. Along with measuring conductance, the wristbands also recorded data on their wearers’ seizures, for later analysis. Those wristbands are still being tested and perfected. Another version of the wrist-worn sensors is being developed for commercial use by Picard’s spin-off company, Affectiva, and is being tested at Brigham and Women’s Hospital.