'All or None' Switch in Brain Determines Epileptic Seizure Severity

Yale University researchers have found a single “switch” in the brains of patients with epilepsy that determines whether an epileptic seizure will be mild or trigger a dangerous, debilitating loss of consciousness.

The study, which was funded by grants from the National Institutes of Health (NIH) and published April 11, 2014, in Neurology, showed there was no gradation of impairment during seizures, as the subjects were either alert or completely unaware of their surroundings.

Hal Blumenfeld, MD, PhD, professor of neurology, neurobiology, and neurosurgery at Yale and senior author of the study, said his research team expected to discover different levels of awareness among epileptic patients who experience focal seizures, which are localized to certain areas of the brain. Instead, they found that patients are able to respond to questions during some seizures, but in other episodes, they are unconscious to their environment.

“During seizures, patients may report a funny, fearful feeling, tingling in their arm, or some quirk in their vision, but are able to answer all our questions,” Blumenfeld said in a statement. “At other times — boom — all of a sudden they are in a daze.”

Blumenfeld said previous studies have shown the “all or none” switch rests in areas of the brainstem that play a part in waking and paying attention to surroundings. The current findings suggest medications that treat narcolepsy or therapies such as deep brain stimulation may help patients with intractable epilepsy.

Although the researchers’ ultimate goal is to prevent seizures, Blumenfeld noted that for one-fifth to one-quarter of epileptic patients, seizures happen no matter what therapies are administered. For those patients, the researchers supposed therapies that can prevent loss of consciousness would greatly improve quality of life.