Epileptic nystagmus.

Two cases of epileptic nystagmus (EN) are described. The first patient had no history of seizures and experienced attacks of EN associated with oscillopsia and followed by horizontal diplopia and esotropia. These episodes could be triggered by certain visual stimuli and ocular pressure. The second patient had a history of generalized tonic-clonic seizures. He displayed episodes of EN that changed direction in the course of the attacks simultaneously with a shift of the EEG discharge from one occipital region to the other. Cortical blindness followed postictally. On recovery from the postictal state, both patients were neurologically normal. With standard electrodes, the EEG seizures associated with EN involved the occipital, posterotemporal, and parietal areas of the scalp contralateral to the fast phase of the nystagmus. In the first patient, use of supplementary scalp electrodes further localized the seizures to an anterior occipital site intermediate between standard occipital and posterotemporal electrodes. Thirty-six previously reported cases of EN were associated with partial seizures. Horizontal EN most commonly results from seizure activity involving the occipital cortex, although participation of adjoining portions of the parietal and temporal cortexes is possible.