[Spike discharges on stimulation with diffuse and patterned light in epileptic and non-epileptic patients (author's...

The effects of photic stimulation with intermittent diffuse light and patterned flash were compared in 587 patients. The diagnosis of epilepsy was unquestionable in 216 patients and suspected in 150 cases while 221 patients had no evidence of epileptic attacks. None of these patients had a history of photosensitive epilepsy. A grid pattern with squares subtending 22' of arc was used in the first 28 patients while the following 379 patients were tested with a checkerboard pattern of corresponding size. In 51 cases generalized spikes or spike-waves and/or occipital spikes were obtained. These discharges were elicited by diffuse light as well as by patterned flash in 37 patients. 11 cases were insensitive to pattern. In 3 cases spike discharges were seen only with patterned light while diffuse light was without effect. The response consisted in 13 cases of generalized spikes and spike-waves. 12 of these had an unquestionable epilepsy. Occipital spikes only were seen in 38 patients; 22 of these suffered from epilepsy. Patterned light was in no case found to be more effective than diffuse light for eliciting generalized epileptic discharges. In the 3 cases where only patterned light produced spikes, these were restricted to occipital regions. As occipital spikes do not have the same significance for the diagnosis of epilepsy as generalized spikes the addition of patterned flash to diffuse light stimulation does not seem to be of great value.