Bitemporal hemianopia in photosensitive epilepsy: a case study

This paper reports the occurrence of bilateral hemianopia in a 16 year old male who was having unusual seizures accompanied by severe migrainous headaches and loss of vision while watching a television programme and while playing with the computer. Electrophysiological tests not only confirmed his photo and pattern sensitivity, but also showed that he had bitemporal hemianopia. Hence, his basic EEG showed a great deal of abnormality including generalised spike and wave activity which was more marked in the temporal regions. The patient showed classical occipital spikes on exposure to 25 and 50 Hz of intermittent photic stimulation. Pattern sensitivity test evoked photo paroxysmal response within the range of 2-4.5 cycles per degree (cpd). The visual evoked response to binocular flash stimulation produced N2 at 74 ms, P2 at 112-118 ms and N3 at 168 ms. P2 amplitude was 15-17 uV. Monocular right stimulation produced N2 at 72 ms, P2 at 122-124 ms. Monocular left stimulation produced N2 at 82 ms, P2 at 120-124 ms of 14 uV and N3 at 178 ms. Pattern reversal stimulation produced some abnormality. Poor phase reversals were mainly seen to the left occiput with right eye stimulation and poor phase reversals to the right occiput with left eye stimulation. The pattern responses were of normal latency but showed a marked hemispheric asymmetry. The reduction of the response in the left hemisphere with right eye stimulation and the reduction in the right hemisphere with left eye stimulation would suggest the presence of bitemporal field deficit.