Prognosis of photoparoxysmal response in nonepileptic patients.

Photoparoxysmal response (PPR) is sometimes incidentally encountered in EEGs performed for evaluation of nonepileptic symptoms. We conducted the first long-term study of a cohort of nonepileptic patients to determine their risk of having seizures subsequent to incidental recording of PPR. After 6 to 12 years (mean, 9 years), none of the 33 patients had had epileptic seizures. To identify prognostic factors associated with PPR, we performed a case-control study comparing the cohort with 33 age-matched patients who had had epileptic seizures prior to PPR recording. There was no statistically significant difference between the two groups with respect to the clinical or EEG data. Morphology of the PPR discharge was not different between the two groups. Contrary to what is widely believed, persistence of PPR discharges beyond stimulation was not associated with a high risk of developing seizures. Prognosis of PPR is age-dependent and seems favorable in adults without previous epileptic seizures.