Morphologic and volumetric analysis of amygdala, hippocampus, fornix and mamillary body with MRI in patients with temporal lobe epilepsy

Abstract

Our aim was to demonstrate lateralization morphometrically and volumetrically measuring the main limbic structures like hippocampus, amygdala, fornix and mamillary bodies in patients with temporal lobe epilepsy (TLE) and to establish the contribution of each anatomical structure to lateralizing the pathological site. Forty-two patients with complex partial seizures originating from the temporal lobe and 42 control healthy volunteers were included in the study. T2-weighted FSE sequences in axial and oblique coronal planes and T1-weighted SE sequences in the sagittal plane were used. A high-resolution IR sequence was used for the volumetric analysis of amygdala and hippocampus and for the measurement of fornix and mamillary body thickness. Intensity changes and atrophy of limbic structures were observed qualitatively and measurement of these structures was performed quantitatively. Student's t test and Mann-Whitney U-test were used for the statistical analysis. The p values <0.05 was taken as statistically significant. Ten out of 42 patients had intracranial masses and were excluded from the study. Qualitative analysis revealed atrophy in 84% and intensity increase in 60% of cases. Quantitative measurement demonstrated that control cases had a larger hippocampus than the patients (p<0.001). There was unilateral hippocampal volume loss in 88% and bilateral volume loss in 13% of patients. There was no difference in the volume of amygdala between the groups (p>0.05). According to the difference in the volumes of the right and left sides, there was unilateral atrophy in 34% of patients. Bilateral atrophy was not observed. There was a significant difference in fornix and mamillary bodies of the patients and control subjects (p<0.005). In 62.5% of cases, there were abnormalities in the fornix with bilateral involvement in 13% of cases. Mamillary bodies were abnormal in 37% of patients with bilateral involvement in 15%. Lateralization was accomplished in 65% of the patients according to the percentage difference ratios of fornix and in 38% of the patients according to the mamillary bodies. It is important to demonstrate hippocampus atrophy in patients with TLE. In the decision of lateralization of the epileptic side, evaluation of the fornix could be a good and practical solution. However, hippocampal volumetry is an indispensable criterion in demonstrating hippocampal atrophy more accurately. Atrophy of the amygdala and thickness of mamillary bodies have the least importance for lateralization.