Abstracts

Rationale: Temporal lobe epilepsy (TLE) with bilateral ictal onset pattern (B TLE) is an intriguing type and its characteristics need to be carefully identified as BTLE patients have been known to be unfavorable surgical candidates. This study aimed to investigate relationship between pre-surgical ictal EEG onset and various clinical factors including laboratory findings in mesial TLE patients who had undergone surgical treatment in Samsung Medical Center. Methods: We systematically reviewed the unilateral mesial TLE patients (n=423) who underwent anterior temporal lobectomy with amygdalohippocampectomy in Samsung Medical Center (from 1996 to 2015). They were retrospectively divided into two groups by ictal EEG onset in pre-surgical video-EEG monitoring: pure ipsilateral ictal onset (n=313) and one or more bilateral/contralateral ictal onset (n=110) to the resection side. The electro-clinical data (demographics, aura, interictal EEG, Engel class) and neuro-imaging (subtraction ictal SPECT coregistered to MRI (SISCOM), positron emission tomography (PET)) data were compared between two groups. Results: In comparison with the bilateral/contralateral ictal EEG onset group, the ipsilateral ictal EEG onset group was significantly older at the seizure onset age (p=0.023) and shorter mean seizure duration (p=0.023). There was a tendeny of increasing number of antiepileptic drugs in bilateral/contralateral ictal EEG group (p=0.078). Whether there are an aura (especially, abdominal and/or psychic aura), febrile convulsion, major head trauma, generalized tonic-clonic seizure or not, there were no statically difference between two groups. The patients who had a bilateral ictal EEG onset were more likely to show bilateral interictal epileptiform discharges (p=0.005). The Engel class and SISOM, PET data had no statically difference between groups. Conclusions: There are electro-clinical differences between patients who had mesial TLE with ipsilateral ictal EEG onset and those with bilateral or contralateral onset. Nevertheless, if the other tests (e.g. semiology, neuroimaging, neuropsychological status) were suggesting unilateral onset, it may not need to hesitate the surgical intervention of the mesial temporal structures. Funding: None