Occipital seizures provoked by intermittent light stimulation: ictal and interictal findings

Occipital seizures provoked by intermittent light stimulation are rare events described in patients with symptomatic and idiopathic epilepsy as well as in nonepileptic individuals. We observed five patients ranging in age from 10 to 32 years, who presented with focal seizures provoked by photic stimuli; none of them had demonstrable occipital lesions. Four patients were epileptic, and one was nonepileptic. Three patients had occipital epilepsy with visual seizures; one had generalized epilepsy with absence attacks; the nonepileptic had migraine. In the patients with visual seizures, interictal EEGs showed occipital foci in two cases and bilateral spontaneous and evoked spikes as well as generalized discharges in the third. The patient with absence attacks had generalized discharges. The migraine patient had a normal EEG. Ictal EEGs showed a focal lateralized theta activity at the onset of seizures in three patients, in one a fast recruiting rhythm intermixed with generalized paroxysms reflex to blinking, and in the other a rapid bioccipital fast rhythm spreading to the anterior regions. Occipital seizures provoked by intermittent light stimulation probably constitute a rare type of photosensitivity, sometimes appearing in occipital epilepsies, generalized epilepsies, and migraine.