Abstracts

Rationale: Sammaritano (1991) reported that localization of primary epileptogenic area is more reliable in rapid eye movement sleep (REM) than in non-REM sleep (NREM) and wakefulness (W) in temporal lobe epilepsy patients. Lateralization of interictal epileptiform discharges (IEDs) during REM, NREM and W was evaluated compared to lateralization using neuroimaging and ictal onset zone on scalp video-EEG in children with intractable epilepsy secondary to tuberous sclerosis complexes (TSC). Methods: 18 patients (9 girls and 9 boys; mean age 7.1 years; range 13 months to 17 years) with intractable epilepsy secondary to TSC who underwent prolonged scalp video-EEG (VEEG) at The Hospital for Sick Children between 2003 and 2007 were retrospectively evaluated. IEDs were visually detected and classified right/left/generalized with minimum of 100 spike-waves, polyspike-and-waves, and sharp waves during REM, NREM and W. Lateralization was defined by location of the largest tuber on MRI and >50% of ictal EEG onset hemisphere. Lateralization of IEDs was compared during REM, NREM and W with the largest cortical tuber and ictal EEG onset hemisphere. Results: 17 subjects were included as one did not have REM recorded during 44-hour VEEG. Five of 17 patients (29 %) had concordant lateralization of MRI and ictal EEG onsets (Group A). There was lateralized MRI but generalized/bilateral ictal EEG onset in 5 patients (29 %) (Group B). There were predominant tubers in bilateral hemispheres but lateralized ictal EEG onset in 4 patients (24 %) (Group C). Two patients (12 %) had predominant tubers in bilateral hemispheres and generalized ictal EEG onset (Group D). The remaining patient (6 %) had predominant tubers in bilateral hemispheres and no electroclinical seizures on scalp VEEG for 96 hours recording (Group E). During REM, 12 (71%) of 17 patients showed the lateralization of IEDs concordant to predominant tubers on MRI and/or ictal EEG onset, consisting of 4 patients (Group A), 4 (B), 4 (C). During NREM, 8 (47%) patients showed the lateralization of IEDs concordant to MRI and/or ictal EEG onset consisting of 3 patients (A), 2 (B), 3 (C). During W, 9 (53%) patients showed the lateralization of IEDs concordant to MRI and/or ictal EEG onset consisting of 3 patients (A), 3 (B), 3 (C). Three patients in group A underwent intracranial VEEG monitoring and cortical resection in the unilateral hemisphere. Post-operatively, these 3 patients in group A became seizure free with antiepileptic drugs after a minimum follow-up period of 8 months (range 8-21 months; mean 13 months). Conclusions: In children with intractable epilepsy and multiple tubers, lateralization of IEDs during REM demonstrated most consistent concordance with predominant tubers and ictal EEG onset hemisphere compared to IEDs during NREM and W. Analysis of IEDs during REM can help lateralize the epileptogenic hemisphere for possible surgical treatments in a subset of children with TSC, despite generalized/bilateral IEDs during NREM and ictal discharges.