Abstracts

Rationale: Propagation of ictal epileptic discharges can influence the clinical appearance of seizures and must be recognized to characterize seizures correctly. Fast propagation from the occipital to the temporal lobe has been very well described, but until now the reverse spread has not been emphasized. The objective of this study is to describe two patients who experienced ictal propagation from temporal to occipital regions during surface EEG. Methods: Out of telemetry studies recorded at the Montreal Neurological Hospital over a ten-year period two patients were found to have ictal propagation from temporal to occipital lobe. We retrospectively reviewed all ictal EEGs of these patients and their seizure semiology. Results: Habitual seizures of patient one presented with altered consciousness, automatisms of the right arm followed by postictal fatigue and headache. Additionally he described an inconsistent aura of anxiety with tachycardia and visual flashes. Telemetry studies suggested a right temporal lobe generator. On one occasion propagation from temporal to occipital was documented on surface EEG during ictal SPECT. The seizure initially involved the temporal lobe followed by rapid spread of the seizure to the ipsilateral occipital lobe. At this time a definite ictal amaurosis was documented lasting a minute before seizure stopped. SPECT revealed widespread tracer enhancement in the right temporal and occipital lobe. Brain MRI studies were normal. Intracranial EEG investigation of both temporal lobes with additional electrodes in the temporo-occipital junction, revealed right temporal onset and rapid propagation contralaterally. The patient underwent a right selective amygdalo-hippocampectomy, but continued to have seizures. The second patient, with a right hemiatrophic hemisphere and porencephalic cyst, presented with seizures that started with an auditory aura, bad smell and a warm sensation in the left arm followed by impaired consciousness. Telemetry suggested a widespread centro-temporal seizure onset. During one noctural event propagation from the temporal to the occipital lobe could be observed on surface EEG. The ictal discharge remained confined to the right occipital lobe for six minutes before seizure stopped. During this period the patient was unresponsive but did not show typical occipital symptoms. Subsequent intracranial electrode investigation showed habitual temporal onset with propagation to the Heschl’s gyrus. After a right mesolimbic and neocortical temporal resection including part of the Heschl’s gyrus patient was free of seizures only temporarily.Conclusions: The two patients showed that propagation from temporal to occipital lobe structures might be observed on rare occasions. Both had clinical and EEG findings suggesting neocortical temporal generators. This rare ictal temporo-occipital propagation pattern must be considered in patients, who have seizures with both temporal and occipital features. The propagation may have predictive value for their surgical outcome.