Influence of ethnic and geographic factors on the classic photoparoxysmal response in the electroencephalogram of epilepsy patients.

The classic photoparoxysmal response (CPPR) on photic stimulation in the electroencephalogram (EEG) of 128 patients with chronic epilepsy, constituting three different ethnic groups, was investigated. All patients were referred for routine clinical EEG investigation. There was a significantly higher occurrence in whites (2.7%, of 72 of 2,657) as compared with blacks (0.1%, 1 of 848) and subjects of "mixed race" (0.9%, 55 of 5,958). Interictal abnormalities and the range of responses were similar in the two main ethnic groups. There was no evidence of a seasonal association with CPPR. We conclude that genetic rather than environmental factors influence the CPPR.