Epileptic nystagmus and its possible relationship with PGO spikes.

A simultaneous video-EEG on a waking 6-year-old male revealed rapid horizontal and then vertical eye movements and 10 sec later showed ictal rhythms maximal on the occipital areas, quickly spreading to all other areas. A second ictal event during wakefulness was very similar to the first. During sleep interictal discharges were seen from the right frontal-temporal area and one more ictal event was noted. This latter seizure in the NREM sleep record did not show any eye movements, but showed ictal activity on the right frontal-temporal area, which later became generalized. We propose that the interictal discharges on the right frontal-temporal area likely arose from the amygdala, which activated the pontine nuclei responsible for PGO (ponto-geniculo-occipital) spikes and the rapid eye movements seen in our patient. The PGO spikes activated the occipital areas, which then showed clear ictal rhythms to complete the sequence of events. This case demonstrates a sequence of rapid eye movements without ictal patterns, followed by seizure rhythms, but may still be an example of "epileptic nystagmus," assuming that the eye movements arose from an ictal activation of the deep subcortical portion of the PGO system.