Abstracts

Several studies have demonstrated diminution in the volume of entorhinal cortex (EC) ipsilateral to the pathological side in patients with temporal lobe epilepsy (TLE). The relationship between the degree of EC atrophy and the epileptogenicity of this structure has never been directly studied. The purpose of the study was to determine whether atrophy of the EC evaluated by quantitative MRI method is correlated with the epileptogenicity of this structure in TLE. Intracerebral recordings (SEEG method) of seizures from 11 patients presenting with mesial TLE were analyzed. Seizures were classified according to patterns of onset: pattern 1 was the emergence of a low-frequency, high-amplitude rhythmic spiking followed by a tonic discharge and pattern 2 was the emergence of a tonic discharge in the mesial structures. A nonlinear measure of SEEG signal interdependencies was used to evaluate the functional couplings occurring between Hippocampus (Hip) and EC at seizure onset. MRI volumetric analysis was performed using a T1-weighted three-dimensional gradient echo sequence in TLE patients and 12 healthy subjects. Significant interactions between Hip and Ec were quantified at seizure onset. The EC was found to be the leader structure in most of the pattern 2 seizures. Volumetric measurements of EC demonstrated an atrophy in 63% of patients. A significant correlation between the strength of EC _ Hip coupling and the degree of atrophy was found. In addition, in those patients that had a normal EC volume, the EC was never the leader structure in Ec-Hip coupling. These results validate the potential role of volumetry to predict the epileptogenesis of the EC in patients with hippocampal sclerosis and MTLE.