Abstracts

RATIONALE: Intractable temporal lobe epilepsy may cause progressive neuronal injury, marked by progressive hippocampal volume loss. Using hippocampal deformation mapping, which can detect subtle hippocampal changes, we assessed for progressive hippocampal volume loss and shape change in a series of patients with intractable temporal lobe epilepsy and sequential volumetric MRI scans.
METHODS: Twenty-two patients undergoing epilepsy surgery for TLE had volumetric MRI scans at initial clinical presentation to our epilepsy center, and at the time of epilepsy surgery. In retrospective review of epilepsy surgery cases, we noted age, sex, duration of epilepsy, frequency of seizures between MRI scans, and dates of sequential MRI scans. We performed hippocampal deformation segmentations of the sequential MRI scans in all patients. Deformation images were grouped into composite images for the initial MRI group and surgical MRI group. Using deformation based hippocampal shape analysis, we calculated volume differences and changes in three-dimensional surface structure in the initial composite and surgical composite MRI images.
RESULTS: The patient group consisted of 10 men and 12 women. Mean age at seizure onset: 10.7 years (range, 1-26 years). Mean duration from seizure onset to first MRI: 21.3 years (range, 3-45 years). Mean duration between first and second MRI: 7.6 months (range, 2-21 months). Mean seizure frequency between first and second MR: 2.8 per week (range, 1-10 per week). The table summarizes volume changes between composite initial and composite surgical MRI scans. Three-dimensional shape analysis, comparing initial and surgical composite hippocampal images, showed accentuated volume loss in the mesial part of the hippocampal head, in the region of the uncinate gyrus for both the right and left composite hippocampi.
CONCLUSIONS: Our series showed significant total hippocampal volume changes in the right hippocampus, and non-significant volume changes in the left hippocampus. Variability in measurements of abnormal hippocampi (Radiology. 2000; 216: 291-297), changes of normal aging, and as well as ongoing epileptic seizures may be responsible for the volume changes. Three-dimensional deformation-based hippocampal shape analysis showed changes of accentuated volume loss in the medial hippocampal head region in both the right and left hippocampi, which may be a region of accentuated involvement from sequelae of ongoing epileptic seizures.[table1]