The Significance and Limitation of MR Volumetry: Comparison between Normal Adults and the Patients with Epilepsy and Hippocampal Sclerosis

ABSTRACT

PURPOSE: Hippocampal atrophy is one of the characteristic pathologic findings of hippocampal sclerosis, for which MR imaging of the hippocampus is essential in the evaluation of hippocampal sclerosis. The purpose of this study is to present the normal MR volumetric data of the hippocampus in normal adult Korean and to compare those with MR volumetric data of hippocampus in patients with hippocampal sclerosis, providing the diagnostic volume criteria of the hippocampal atrophy. MATERIALS AND METHODS: MR volumetry was performed in 30 normal adults and 28 patients with temporal lobe epilepsy whose final diagnosis was hippocampal sclerosis. The volumetric data were compared between sexes, right and left sides, and normal and abnormal hippocampus, and the volume criteria for the diagnosis of hippocampal atrophy was determined. RESULTS: The mean volumes(+/-standard deviation) of normal Korean adult were 2.20+/- 0.73 cm3 (right) and 2.17+/-0.72 cm3 (left) in male and 2.27+/-0.47 cm3 (right) and 2.23 +/-0.48 cm3 (left) in female. The mean right-left differences were 0.14+/-0.11 cm3 and 0.19+/-0.13 cm3 in male and female, respectively. The MR volumetry showed no significant statistical differences between sexes and between right and left. The mean volume and standard deviation of the hippocampus in hippocampal sclerosis patients was 1.46+/-0.60 cm3, and the right-left difference was 0.51+/-0.41 cm3. In comparison of two volume distributions between normal adult group and hippocampal sclerosis patients group, the reasonable diagnostic volume criteria was 0.4 cm3 as right-left volume difference, in which the sensitivity and specificity are 0.61 ant0.90. In all patients with right-left volume difference more than 0.4 cm3, visual determination of unilateral hippocampal atrophy was possible. CONCLUSION: The MR-based hippocampal volumetry is a useful add-on of visual MR diagnosis, only when visual diagnosis of hippocampal sclerosis is difficult.