Abstracts

RATIONALE: A subpopulation of patients with unilateral drug-refractory temporal lobe epilepsy (TLE) has a volume reduction in the ipsilateral entorhinal cortex (EC) in MRI. This study investigated the distribution of damage along the various rostrocaudal levels of the EC which are known to have different connectivity with other brain areas. METHODS: Volume of the EC was measured in 29 patients with unilateral drug-refractory TLE and 20 age-matched controls with 1.5 T Magnetom (Insausti et al. AJNR 1998:19;659-671). All patients were evaluated for epilepsy surgery and subsequently operated on. Twelve patients had seizure focus on the left and 17 on the right. The total volume of the EC was divided rostrocaudally into 5% consequent volume segments. In addition, we compared the volumes of the rostral, mid, and caudal thirds of the EC between the groups. Nonparametric Kruskall-Wallis and Mann-Whitney tests with Bonferroni correction were used for comparisons. RESULTS: In left TLE, the total volume of the ipsilateral EC was reduced by 17% (p<0.01, compared to controls). Volume reduction was most prominent at the rostral and caudal thirds of the EC (p<0.05 and p<0.05). In left TLE with hippocampal damage, volume reduction extended throughout the entire rostrocaudal axis of the EC (p<0.05). In right TLE, total volume of the ipsilateral EC was reduced by 13% (p<0.01) in cases with hippocampal atrophy (n=11) and the damage was most prominent in the mid portion of the EC (p<0.05). CONCLUSIONS: Volume reduction in the EC is encountered more often in the rostral and caudal aspects of the EC than in its mid portion.