Entorhinal cortex involvement in human mesial temporal lobe epilepsy: an electrophysiologic and volumetric study.
OBJECTIVE
Several studies have demonstrated diminution in the volume of entorhinal cortex (EC) ipsilateral to the pathologic side in patients with temporal lobe epilepsy (TLE). The relation 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 the quantitative magnetic resonance imaging (MRI) method is correlated with the epileptogenicity of this structure in TLE.


METHODS
Intracerebral recordings (SEEG method) of seizures from 11 patients 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 by using a T(1)-weighted three-dimensional gradient-echo sequence in TLE patients and 12 healthy subjects.


RESULTS
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 ipsilateral to the epileptic side. 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.


CONCLUSIONS
These results validate the potential role of volumetry to predict the epileptogenesis of the EC in patients with hippocampal sclerosis and MTLE.
Bartolomei
Fabrice
F
Service de Neurophysiologie Clinique et Epileptologie and INSERM EMI 9926 CHU TIMONE et Université de la Méditerranée, Marseille, France. fbartolo@medecine.univ-mrs.fr
Khalil
Mouhamad
M
Wendling
Fabrice
F
Sontheimer
Anna
A
Régis
Jean
J
Ranjeva
Jean-Phillipe
JP
Guye
Maxime
M
Chauvel
Patrick
P
D000293:Adolescent; D000328:Adult; D001284:Atrophy / Q000473:pathology; D001931:Brain Mapping; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data*; D004594:Electrophysiology; D018728:Entorhinal Cortex / Q000473:pathology* / Q000503:physiopathology*; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008991:Monitoring, Physiologic; D020534:Parahippocampal Gyrus / Q000473:pathology / Q000503:physiopathology; D012044:Regression Analysis; D014743:Videotape Recording