Abstracts

Rationale: Temporal lobe epilepsy (TLE) is the most common form of localization related epilepsy considered for epilepsy surgery. Interictal/ictal EEG and clinical data, with conjuction magnetic resonance imaging (MRI) results predict the localization of the epileptic zone in the patient with TLE. An important goal in the pre-surgical evaluation of patients with medically intractable TLE is to quantify hippocampal pathology bilaterally. The purpose of this study is to determine whether interictal apparent diffusion coefficients (ADC) provide a robust means for detecting hippocampal abnormalities in adult patients with chronic TLE undergoing pre-surgical evaluation. Methods: We examined contribution of diffusion weighted magnetic resonance imaging (DWI) and ADC values for the lateralization of lesion in twenty-six patients (14 female, 12 male; mean age 29 years) with TLE. Twenty healthy subjects served as controls (5 male, 15 female; mean age 29 years). The diagnosis of TLE was based on semiology, interictal EEG, video EEG monitoring, and conventional MRI. In both groups ADC values which were obtained from hippocampus in coronal plane were compared. Diffusion-weighted spin echo echoplanar images (EPI) were acquired with standard head coil for signal reception. In patient group, ipsilateral and contralateral ADC values to the seizure focus were compared. Results: We determined focal epileptiform discharges in %84 of patients by EEG, and hippocampal zone abnormality in %73 of patients by DWI. Ipsilateral hippocampal ADC values (100,09 7,15 x 10-5 mm2/sec) which were determined in the basis of EEG lateralization were considerably higher than the contralateral side values (85,58 1,83 x 10-5 mm2/sec) and the same side values of controls (p<0,001). There was not a significant difference between the contralateral side ADC values of patients and controls. We could not find bilateral hippocampal abnormality in MRI, whereas DWI showed bilateral changes in %19 of TLE patients. There was no any relationship between ADC values and clinical variables such as sex, duration of epilepsy, frequency of seizures, and history of febrile convulsion/status epilepticus. The results demonstrated a correlation between lateralizing ictal semiology and ADC values (Spearman r = -0,643; p = 0,033).