Abstracts

Rationale: A subset of children with intractable focal epilepsy has generalized interictal epileptiform discharges (GIED). The purpose of this study is to clarify whether lateralization of interictal epileptiform discharges (IED) in rapid eye movement sleep (REM) is concordant with epileptogenic hemisphere in children with GIED and intractable focal epilepsy. Methods: We reviewed 103 children who underwent intracranial video-EEG (IVEEG) at The Hospital for Sick Children in Toronto, Canada from July 2004 to January 2012. We retrospectively identified GIED in non-REM sleep (NR) during presurgical scalp video-EEG (VEEG). We collected a minimum of 100 IED in NR, REM, and wakefulness (W) respectively, and assigned lateralization; left hemisphere (L), right (R), or generalized (G). Predominant IED ratio (the highest number among L or G or R IED / Total IED) was calculated in each state. GIED ratio consists of GIED / Total IED. Lateralization of each state was compared with surgical hemisphere. Results: We studied 25 children (15 girls, 10 boys) who had GIED in NR. Twenty-three children (92%) had normal neurological examinations. Mean GIED ratio was 66% in NR, 34% in REM and 55% in W. Nineteen (76%) children showed lateralized predominant IED in REM significantly higher than in NR (5 children, 20%) and W (12, 48%). All lateralized predominant IED in each state were concordant with surgical hemisphere. Twenty-one of 22 children underwent multilobar resection in one hemisphere and one child frontal lobectomy. Remaining 3 did not undergo resective surgery due to overlapping seizure onset zone and eloquent cortex. One child with multilobar resection was lost to follow-up. Sixteen of 21 (76%) children became seizure free. Eleven (52%) children had no deficit post-operatively, four (19%) had hemiparesis, three (14%) mild weakness, two (10%) homonymous hemianopia, and one (5%) dysarthria. Conclusions: Lateralized IED in REM sleep identified epileptogenic hemisphere despite GIED. Multilobar cortical excision using IVEEG achieved good seizure outcome in a subset of children with intractable focal epilepsy and GIED.