Pat Semien's son, Ryan, had epilepsy since he was two years old. His family worries.
"When the phone rings or we hear a thud," said Pat.
Epilepsy is a short circuit in the brain that can cause convulsions or in Ryan's case...
"There is a blank stare. There is a tremor," said Pat. "You know right away something's not right."
Ryan has tried some 20 medications. Nothing has stopped them.
"He worries every day that it could happen," Pat told us.
But seizures that cause death, like the case of Jett Travolta are a rare occurrence, according to Texas Children's Hospital pediatric epileptologist Dr. James Riviello.
Dr. Riviello says seizures most likely to cause SUDEP, or 'sudden unexplained death in epilepsy,' are...
"Nocturnal seizures, seizures during sleep, and what people call a grand mal seizure. Those seem to be the ones where people are at the most risk," he said.
A lethal seizure can stop breathing. Vomiting can go into the lungs, also interfering with breathing. It may interfere with heart rate. A seizure in water, even a bathtub, can cause drowning. A fall can cause a lethal head injury.
If you see someone having a seizure, get them to the floor or a safe place.
"Turn their head to the side, lift their chin up because that will open up their airway, and turning their head to the side because if they do vomit, the vomit will go out of their mouth and not into their lungs," said Dr. Riviello.
Thirty percent of people with epilepsy, like Ryan, have seizures that can't be controlled.
"If I could have one wish that would be it -- for Ryan to be seizure free," said Pat.
Some three million Americans have epilepsy. The Epilepsy Foundation of Texas can answer questions about lethal seizures. Call them at 713-789-6295 or reach them through their website.
Christi Myers is ABC13's Healthcheck reporter