Prevalence of photoparoxysmal response among South Indian epilepsy patients

The reported geographical variations in the prevalence of photoparoxysmal response (PPR) among epilepsy patients have been variously attributed to methodological problems such as patient selection, technique of intermittent photic stimulation (IPS) and definition of PPR, and environmental and racial factors. We determined the prevalence rate of PPR among South Indian epilepsy patients and compared it with the rates reported from elsewhere. Twenty of our 575 patients had a PPR, a prevalence ratio of 3.5%, which is in striking contrast to the 0.6% reported for North Indian epilepsy patients. Environmental and racial factors cannot explain the difference in the prevalence rates of PPR between South and North Indian epilepsy patients. We conclude that the demographic characteristics of the patient group, such as age and gender, the epilepsy type, sleep deprivation, technique of IPS and definition of PPR, greatly influence the prevalence rate of PPR.