Abstracts

In epilepsy surgery decisions are made by convergent datas from seizure semiology, electroencephalography, neuropsychology and imaging methods. In this study we analysed the distribution and maxima of interictal spiking (epileptogenic zone, EZ) and seizure onset (SZO) in patients with histologically verified hippocampal sclerosis (HS) compared to patients with extrahippocampal pathology (NHS)., We included 182 patients, 81 patients with HS and 101 patients with extrahippocampal pathology. All patients had an EEG work up with closely spaced surface and sphenoidal electrodes (SP 1/ 2)., In NHS patients there was a much more widespread involvement of surface electrodes than in HS patients. In HS patients we had a more frequent maximum in SP 1/ 2 (60/38%) than in NHS patients which was significant (p [lt] 0,004). The sensitivity was 60% , the specificy 62%:Ictally we had a much more widespread onset maximum in NHS than in HS. SP 1/ 2 maximum in HS with 64% was significant higher (p[lt] 0,001) than in NHS (33%). The distribution of EZ and the SZO maximum together resulted in a moderate sensitivity with 74% (p[lt] 0,001)., Interictal and ictal involvement of SP 1/ 2 in HS patients is significantly higher than in NHS patients. But related to the moderate sensitivity the separation of hippocampal (HS) from extrahippocampal pathology is not possible in a single case. Only the mode of distribution of the involved electrodes together with adequate imaging can help to delineate the epileptogenic zone and to separate hippocampal from extrahippocampal cases.,