Abstracts

Rationale: Video-EEG monitoring remains as one of the cornerstones of the presurgical evaluation of patients with refractory temporal lobe epilepsy (TLE). Hippocampal sclerosis (HS) is the most common type of lesion observed in mesial TLE. Several studies have already demonstrated the progression of HS on MRI. When interictal epileptiform discharges (IED) are unilateral, the lateralizing value of ictal scalp EEG is significantly better when compared to bilateral IEDs. A longer duration of epilepsy is related with a worse post-surgical prognosis.The aim of this study was to evaluate if there was any correlation between duration of epilepsy, video-EEG findings and hippocampal neuronal cell density.Methods: Seventy patients with medically refractory TLE were included in the study. All had extensive presurgical evaluation including 1.5T MRI with unilateral HS, prolonged noninvasive video-EEG, and neuropsychological testing. Histopathological analysis was performed on the hippocampal tissue of all patients. Neuronal cell density was noted. Patients were divided into two groups, according to the interictal EEG: unilateral or bilateral (≥20% of independent interictal discharges in the side contralateral to the HS). Statistic method: ANOVA (p=0,05) and Spearman's test.Results: Seventy patients (37 women) were included and their age varied from 17 to 62 years (37.5± 11.3), mean duration of epilepsy of 23.5 years (from 4.0 to 56). Thirty eight had right HS. The mean age in the beginning of epilepsy was 14.1 (± 9.64), 52.9% of them had an initial precipitating injury (IPI) and febrile seizure was the most frequent (38.9%). There was no statistical significant correlation between duration of epilepsy and interictal EEG and (p=0,866). Patients with unilateral interictal EEG had a lower neuronal cell density in CA2 compared to the bilateral group (p=0.029). Besides that, those with longer duration of epilepsy had a lower neuronal cell density in CA3 (p=0.030) and CA4 (p=0.039).Conclusions: Clinical data were concordant with those in literature, with the majority of patients presenting an IPI and more specifically febrile seizure¹. TLE related to HS has been thought to be a progressive disorder since patients experience silent periods before seizures become refractory to medical treatment. Documented in several imaging publications²,³, our study shows the progression of atrophy at histological level. References: 1.Janszky J, Janszky I, Schulz R, Hoppe M, Behne F, Pannek HW, Ebner A. Temporal lobe epilepsy with hippocampal sclerosis: predictors for long-term surgical outcome. Brain 2005;128(Pt 2):395-404. 2.Bernhardt BC, Worsley KJ, Kim H, Evans AC, Bernasconi A, Bernasconi N. Longitudinal and cross-sectional analysis of atrophy in pharmacoresistant temporal lobe epilepsy. Neurology. 2009;19;72(20):1747-54. 3.Bernhardt BC, Kim H, Bernasconi N. Patterns of subregional mesiotemporal disease progression in temporal lobe epilepsy. Neurology. 2013;19;81(21):1840-7.