A recent finding may indicate brain irritability or hypersensitivity in children with autism spectrum disorders.
BALTIMORE—The incidence of a photoparoxysmal response among children older than 15 with autism spectrum disorders (ASD) is 25%, which is much higher than that for younger children with ASD, according to a study presented at the 65th Annual Meeting of the American Epilepsy Society. When children in the sample population without epilepsy are excluded, the incidence of a photoparoxysmal response among children older than 15 with ASD is 29.4%.
Epilepsy and frequent interictal discharges are common among children with ASD. Photoparoxysmal responses are interictal EEG discharges correlated with generalized, photosensitive epilepsy. A flashing strobe light, for example, can trigger a photoparoxysmal response in a predisposed individual. “The brain picks up that stimulus through the eye, and for some children, it can cause an abnormal brainwave pattern,” explained Jill Miller-Horn, MD, an epilepsy fellow at Children’s Hospital Boston.
“We already know that abnormal brainwave responses to flashing light can be associated with epilepsy. You might be familiar with what happened in Japan with the Pokemon cartoon, where there was bright, flashing colored light on the screen and hundreds of children then had seizures,” she added. Dr. Miller-Horn and her colleagues decided to study photoparoxysmal responses to photic stimulation in children with ASD, a topic that she said no researchers had previously investigated.
Identifying a Cohort of Children With ASD
The team conducted a retrospective pilot study of children with ASD to determine the rate of the photoparoxysmal response caused by intermittent photic stimulation during EEG studies at Children’s Hospital Boston. The investigators searched medical records that identified 333 children with ASD who were treated at the hospital between December 2010 and May 2011.
Of these children, 206 had had EEGs. In the group of 206 children, 118 had comorbid ASD and epilepsy, and 88 had ASD without seizures. Intermittent photic stimulation was part of 177 children’s EEG studies. The group of 177 included 138 boys and 39 girls, and the children’s average age was 9.
Photoparoxysmal Response Increases in Adolescence
A photoparoxysmal response was elicited in 13 of the 177 children who received photic stimulation during their EEGs. The 7.3% incidence of a photoparoxysmal response in children with ASD was within the range previously reported in the normal population, according to Dr. Miller-Horn. “Our study found that in the ASD population, there is an association between the photoparoxysmal response and epilepsy, as has been previously reported in children with epilepsy without ASD,” she said.
“When we subdivided these children with autism by age, we found that there’s an increase in the photoparoxysmal response as they entered adolescence,” commented Dr. Miller-Horn. The meaning of the result is unclear, “but it’s a difference from the normal population, and it’s a difference from other children who have epilepsy,” she added.
“This is a new finding that may be a clue to the pathophysiology for the high rate of ASD and epilepsy comorbidity,” Dr. Miller-Horn continued. “There may be irritability or hypersensitivity in the brain for children with autism that’s being revealed with the clue that they are more photosensitive.”
Large-scale and prospective studies are needed to confirm the trend, according to the investigators. Further studies could reveal the findings’ significance in the pathophysiology of epilepsy in children with ASD.