Incidence of photosensitive epilepsy in unselected Indian epileptic population.

The recognition of photosensitivity depends upon the finding of an abnormal EEG response to intermittent photic stimulation (IPS). Photosensitive epilepsy being the most common form of reflex epilepsy, has been studied most extensively and is reported to account for 5-10% of the epileptic population in general. One thousand unselected epileptics hailing from different parts of Northern India were screened for photosensitivity, both clinically and on a standard protocol of IPS-provoked EEG recordings. Six patients (mean age 14.5 +/- 3.56 yr) were found to be photosensitive: 4 had generalized, 1 had complex partial and 1 mixed seizures; 3 had history of seizures provoked by visual stimuli. The baseline EEG in 4 patients showed generalized and 2 partial, with secondary generalized, epileptiform discharges. On IPS, similar EEG findings were obtained with a wide range of stimulus frequency (6-60 cycles/s). There is a low incidence of photosensitivity in our epileptic population, for which we believe, genetic factors are responsible.