Abstracts

Rationale: The progression over time of structural damage in mesial temporal lobe epilepsy (MTLE) is a matter of debate especially in patients without hippocampal sclerosis (HS). The objective of the present study was to evaluate and compare the occurrence of structural abnormalities over time in MTLE with MRI signs of HS (MTLE-HS) and MTLE with normal MRI (MTLE-NL). Methods: We evaluated 139 adult patients with refractory unilateral MTLE. Patients were divided in MTLE-HS (N=77) or MTLE-NL (N=62) according to visual analysis plus automatic hippocampal volumetry of a 3T MRI protocol. Time of active epilepsy was defined as the age at MRI scan minus the age of epilepsy onset minus periods of seizure remission higher or equal to two years. Patients were divided according to the distribution of duration of active epilepsy: short epilepsy duration (up to 20 years of active epilepsy) or long epilepsy duration (more than 20 years of active epilepsy). For detection of subtle gray matter (GM) atrophy, voxel-based morphometry (VBM) was performed with VBM8/SPM8 (two-sample T-Tests, p=0.001, minimum of 30 contiguous voxels) in T1-weighted images acquired in a 3T scanner. Patients with the epileptic focus at the right side had their images flipped in the right-left orientation. Healthy subjects paired to sex and age for the analysis of each subgroup were used as comparison (29 to 39 individuals). Results: MTLE-HS patients with both short (38 patients) and long epilepsy duration (33 patients) had diffuse gray matter atrophy including mesial and neocortical temporal structures, thalamus, precentral gyrus, precuneus and cuneus ipsilateral to the epileptic focus; however, in patients with long epilepsy duration, extra-hippocampal GM atrophy was more pronounced and included bilateral structures. MTLE-NL patients with short epilepsy duration (39 patients) had only a small area of GM atrophy in the contralateral superior frontal gyrus while MTLE-NL with long epilepsy duration (29 patients) had diffuse GM atrophy including bilateral precentral gyrus, ipsilateral thalamus and precuneus (Figure 1).Conclusions: both MTLE-HS and MTLE-NL the gray matter atrophy is more pronounced in patients with long duration of active epilepsy. These findings support the evidence that progression of gray matter atrophy occurs in MTLE irrespective of the presence of HS.