Clinical significance of photic stimulation during routine EEGs of adult patients.

Intermittent photic stimulation (IPS) is an activating procedure meant to elicit or accentuate epileptiform discharges during an EEG. There is insufficient clinical data to advocate IPS in the routine EEGs of all adult patients. We therefore sought to address the clinical significance of routine IPS in the adult population. We retrospectively reviewed 100 consecutive abnormal EEGs in adult patients (inpatients and outpatients) who had undergone photic stimulation in our laboratory. Nine patients had abnormalities noted during IPS. The abnormalities consisted of sharp waves in four patients and focal slowing in five patients. Only one patient had abnormalities on IPS that provided information additional to that seen on the baseline record.