Patterns of intrahemispheric propagation in pediatric photoparoxysmal response

The photoparoxysmal response (PPR) is the most important EEG indication of photosensitivity (PS). It may be elicited by intermittent photic stimulation (IPS). PS mostly affects young individuals, with adolescent females at greatest risk. The diagnosis of PS is based on visual EEG assessment. To date, no objective test of PS has been established.

Here we describe 89 individuals of both sexes, aged 5-18 years, epileptic and non-epileptic, in whom a PPR was elicited by IPS during a standard EEG procedure. The distribution of amplitude and intrahemispheric coherence indices were analyzed and, in each case, revealed a unique pattern of PPR propagation.

A lateral (occipito-temporo-frontal) track was found in 52% of recordings, and 55% of individuals tested showed symmetric patterns. A bilateral pattern dominated in all age groups, all grades of PS, and across epileptic and non-epileptic groups.

A symmetric, bilateral pattern is the most common type of PPR across genders and all ages, regardless of grade of PS and the presence of epilepsy. The results of this study show the current PPR classification in a new light and provide a basis for the concept of PPR lateralization based on objective, quantitative findings.