Abstracts

Ictal nystagmus is a rare sign of seizure activity and has been reported very rarely. We studied an 29 year male patient with nonconvulsive simple partial status epilepticus arising from right posterior temporo-occipital area presenting as a pure ictal nystagmus with left homonymous hemianopsia, which gave us a good opportunity to make it clear to understand the underlying mechanism of epileptic activation of ictal nystagmus. EEG including electrooculogram and electronystagmogram was done during ictus. Brain MRI, ^99mTc-ECD SPECT and ¹⁸F-FDG PET were done during ictus and repeated after clinical improvement. Comparison between the area of glucose uptake and those of blood hyperperfusion was done through subtraction image in each of the study. Pure horizontal nystagmus without conjugate deviation or head turning to one side showed clear focal EEG onset from right posterior temporo-occipital electrodes without spread to contralateral hemisphere. The electronystagmogram during ictus revealed typical linear slow phase with midline cross of the eyeball clinically, which meant epileptic activation of cortical smooth pursuit system. Subtraction images from SPECT and PET revealed clear distribution of epileptic activation in the right posterior temporo-parieto-occipital lobe, but the area of glucose uptake was much wider than those of hyperperfusion. We reports the case with ictal nystagmus by activation of cortical smooth pursuit system who had nonconvulsive partial status epilepticus presenting as a pure ictal nystagmus. The neuroimages reveals the relevant area of epileptic activation from smooth pursuit system is the posterior temporo-parieto-ooccipital area. This case suggests that activation of cortical smooth system could be directed to pulse generator in pontine independent of connection to frontal eye field, could result in ictal nystagmus.