BALTIMORE – Nearly one-third of older teens with autism spectrum disorders and comorbid epilepsy also had a brain wave pattern associated with seizure-related light sensitivity.

The interictal EEGs of these teenagers showed a photoparoxysmal response to a flashing strobe light, Dr. Jill Miller-Horn said at the annual meeting of the American Epilepsy Society. The incidence of photoparoxysmal response sharply increased with age, she said – a finding that could speak to environmental factors that influence this EEG patterns in children with autism.

"By age 15, this response [to a strobe light] had skyrocketed to a high degree," Dr. Miller-Horn said in a press briefing. The finding rose to 30% among teens older than 15 years.

The meaning of this association is yet to be determined, but it may speak to environmental factors, such as exposure to television or video programs, computer screens, or even the classic hand-flapping behavior of autism that can mimic a flickering light, she said. Children with the photosensitive response might be more apt to have a seizure when exposed to any of these factors, or a rapidly shifting light and shadow.

In fact, about half of the group (7 of 13) also displayed a behavior that could be associated with flickering light, including eyelid flutter, hand flapping, prolonged blink and eye closure, and eyelid fluttering.

The retrospective study by the Children’s Hospital Boston researchers involved 206 children with autism; of these, 118 also had epilepsy. Most (117) underwent intermittent photic stimulation EEG between seizures. A photoparoxysmal response (PPR) occurred in 13 children (11%).

Most of these children (11) had comorbid epilepsy: generalized tonic clonic seizures (5); myoclonic seizure (2); electrical status epilepticus of sleep (1); and atypical absence (1). Two children had complex partial seizures. Two did not have epilepsy but still displayed the abnormal interictal epileptiform brain activity. The PPR was more common in those with comorbid epilepsy than in those with autism alone (12% vs. 1%).

Dr. Miller-Horn examined the incidence of PPR in different age groups. It was most common among teens older than 15 years, occurring in 30% of those with comorbid autism and epilepsy. Among children aged 10-15 years, 10% of those with both disorders had a PPR. The response was present in 7% of children aged 6-9 years and 8% of those aged 0-5 years who had both disorders.

The rate was still unexpectedly high among children with only autism, and showed a similar age-related pattern: 25% of those older then 15 years; 7% of those aged 10-15 years; 5% of those aged 6-9 years; and 4% of those aged 0-5 years.

This finding has never been reported, and as such, doesn’t merit a recommendation to parents of children with autism and epilepsy. "It’s not enough to recommend that parents put any limitations [in TV, computer, or video viewing] on these children, she said. "We would need more research."

Dr. Miller-Horn said she had no relevant financial disclosures.