Abstracts

Intermittent photic stimulation (IPS) is used routinely as an activation procedure for electroencephalographs (EEGs) in the pediatric population. Photosensitivity is relatively more prevalent in children than in adults. The purpose of this study was to determine the proportion of pediatric epilpetiform EEGs in which photic stimulation altered the overall impression of the EEG, thus adding additional information to the baseline. One hundred consecutive EEGs performed at the University of Alberta Hospital on patients 18 years or younger, that had unequivocal epileptiform abnormalities and activation by IPS were reviewed. Demographics including patient age, sex, clinical diagnosis, and reason for the EEG were collected. A determination was made as to whether IPS altered the overall impression of the EEG. There were 62 males and 38 females. Forty-two patients were noted to have photic driving. Fifty patients had evidence of epileptic activity during photic stimulation, which was determined not to be linked to the stimulus. In 3 patients, there was epileptic activity during IPS with possibile association to the stimulus. In 3 patients IPS provided information not available otherwise. Out of these 3 patients, one had photosenstive Juvenile Myoclonic Epilepsy, the second had occipital spikes that generalized during IPS, and the third patient had evidence of occipital dominant spikes and polyspikes during IPS, a finding not seen on the baseline EEG. The finding of photosensitivity did not alter the management plan for any of these patients. This study demonstrates a prevalence of 3% photosensitivity amongst pediatric patients with known epileptic abnormalities on their EEG. These numbers are lower than those described by Wolf and Goosses (1), who reported a prevalence of 10%, in their review of of more than 1000 patients. The discrepancy could be related to the difference in sample size or merely to genetic heterogenity in the different samples. Interestingly all our photosensitive patients were females supporting the previously published literature on higher prevalence of photosensitivity in females. Considering the prevalence of photosensitivity in the epileptic population and the benign nature of the procedure, we support this activation procedure in routine practice.

Wolf P, Goosses R. Relation of photosensitivity to epileptic syndromes. [italic]J Neruol Neruosurg Psychiat[/italic] 1986;49:1386-1391.