Mental imagery of photic stimulation provokes paroxysmal EEG activity in a photosensitive patient who self-induces seizures

Abstract

This article reports a case of a 14 year-old male photosensitive epileptic patient who was able to induce fits subjectively by the mental imagery of the effective visual stimuli. The patient underwent a comprehensive electroencephalographic (EEG) examination including hyperventilation. The basic EEG showed abnormalities. Intermittent photic (IPS) and pattern stimulations (PtnS), evoked photo and pattern paroxysmal responses (PPRs) within a wide range of frequencies for 2-50 flashes per second (fps) and 0.5-6 cycles per degree (cdp) respectively. The patient was able to reconstruct the PPRs mentally on exposure to the effective stimuli of 25 and 50 fps, and 2.0 and 3.25 cpd respectively. His cognitive functions were not affected when exposed to photostimulation. However, on exposure to pattern stimulation, he became totally confused and his consciousness was impaired. These findings showed that self-induction of fits in photosensitive epilepsy is a mental phenomenon which takes place with or without loss of cognitive function depending on the rate and frequency of the physical and 'imagined' stimuli.