A sweat-sensing wristband that can tell the difference between a relatively safe seizure and one that could kill you has been developed by scientists.
The device works as accurately as an electroencephalogram (EEG), the current standard for gauging seizure severity, and may even be able to predict seizures without the patient even needing to come into hospital.
The wristbands measure skin conductance, or how easily an electrical current can travel across the skin, which is related to how much an individual sweats.
The bracelet is a useful way to measure how emotionally aroused a person is, But it cannot tell which specific emotion is being felt because sweat glands are activated only by the sympathetic nervous system, which controls the fight-or-flight response.
When something fires you up or sends chills down your spine, your skin conductance goes up.
"The sensors are wireless and comfortable, so we can do experiments in the field," New Scientist quoted Javier Hernandez Rivera of the MIT Media Lab in Cambridge, Massachusetts, as saying.
Rosalind Picard and colleagues at the Media Lab initially developed the wristbands to study the emotional states of children with autism who can't always communicate what they're feeling.
One of her undergraduate students took the sensors home over their winter break to test them out on his autistic brother.
One day shortly after Christmas, Picard noticed an enormous spike in activity in one wristband, but not the other. The student checked his records and realised that the peak came 20 minutes before his brother had a seizure.
"This was a total accidental finding," she said.
For the study, researchers fitted wristbands on 11 children who were being evaluated as candidates for brain surgery. They recorded a total of 34 seizures.
They found that the higher a patient's skin conductance during a seizure, the longer it took their brainwaves to return to normal conditions afterwards.
The wristbands also picked up on seizure signals earlier than EEGs in some cases. EEG can only pick up activity in the cortex, the outer layer of the brain.
"If the seizure starts in the amygdala, the EEG won't see it, but the skin sensors will," Picard said.
This necessarily doesn't mean that the wristbands can predict seizures before they happen.
"We think we can predict, but we can't claim that yet.
"We need more data," Picard added.