MR measurements of the hippocampus for lateralization of temporal lobe epilepsy: value of measurements of the body vs the whole structure.

OBJECTIVE: Measurements of the volume of the hippocampus have been used preoperatively to determine the side of the hippocampus involved in patients with intractable temporal lobe epilepsy. However, the method used is time consuming and requires special training. The purpose of this study was to determine the validity of using measurements of the volume of the hippocampal body as a substitute for measurements of the volume of the whole hippocampus in patients with temporal lobe epilepsy. SUBJECTS AND METHODS: The study group consisted of 33 patients with intractable temporal lobe epilepsy due to presumed hippocampal sclerosis and 30 control subjects. Of the 33 patients with intractable temporal lobe epilepsy, 30 had hippocampal sclerosis and three had normal findings on pathologic examination of the hippocampus. T2-weighted fast spin-echo images were used to determine hippocampal volumes. Volumes were calculated by summing the sectional areas of the entire hippocampus and of the hippocampal body. Correlation between the volume of the hippocampal body and the volume of the whole hippocampus was determined. The sensitivity and specificity of measurement of the volume of the hippocampal body for lateralizing the foci responsible for seizures in patients with presumed hippocampal sclerosis were compared with those of measurement of the volume of the whole hippocampus. RESULTS: Significant linear relationships were noted between volumes of the hippocampal body and volumes of the whole hippocampus (p < .001). The sensitivity and specificity of measurements of volumes of the hippocampal body were identical to those of measurements of volumes of the whole hippocampus (87% and 100%, respectively). CONCLUSIONS: Our results show that segmental MR measurements of the body of the hippocampus are as accurate as measurements of the whole hippocampus for lateralizing temporal lobe epilepsy before surgery. Because segmental measurements are less time consuming and require less experience to perform, they are considered the procedure of choice.