Clues to Why Epileptic Seizures Can Halt Breathing

Higher levels of the brain chemical serotonin are linked to a lower risk of potentially deadly seizure-related breathing pauses in people with epilepsy, researchers say.

The findings suggest serotonin may help protect people with epilepsy from this threat, according to the authors of the study published in the Sept. 4 online issue of the journal Neurology.

"Serotonin, a hormone that transmits signals between nerve cells in the brain, is known to regulate breathing and waking from sleep, but what is unknown is how it may influence breathing before, during and after seizures," study author Dr. Samden Lhatoo said in a journal news release.

Lhatoo is a professor of neurology at the University of Texas' McGovern Medical School in Houston.

"Our findings show that higher levels of serotonin after a seizure are associated with less breathing dysfunction, and while we cannot make any links between serotonin levels and a risk of sudden unexplained death in epilepsy [SUDEP], our research may provide some important clues, since SUDEP has been linked in previous research to profound breathing dysfunction after generalized convulsive seizures," said Lhatoo, who conducted the research at Case Western Reserve University in Cleveland.

The study included 49 patients, average age 42, with hard-to-treat epilepsy. While in an epilepsy monitoring unit, electrical activity in their brain and heart, blood-oxygen levels, and changes in blood flow were assessed during an epileptic seizure.

To measure serotonin levels, blood samples were collected within about 10 minutes of a seizure and again at least 12 hours later.

In all, 35% of patients temporarily stopped breathing during seizures and 30% temporarily stopped breathing afterward.

Serotonin levels after a seizure were higher than before it in patients who did not temporarily stop breathing either during or after the event. Among patients who did temporarily stop breathing, serotonin levels were not significantly higher before or after a seizure.

"Our results give new insight into a possible link between serotonin levels and breathing during and after seizure," Lhatoo said.

He said this gives hope that new therapies could be developed in the future to help prevent sudden unexplained death in epilepsy. But, he added, the current study was small and more research is needed to confirm the findings.

"It is also important to note that excess serotonin can be harmful, so we strongly recommend against anyone trying to find ways to increase their serotonin levels in response to our study findings," Lhatoo concluded.

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