SEVERITY OF HIPPOCAMPAL ATROPHY CORRELATES WITH THE PROLONGATION OF MRI T-2 RELAXATION IN TEMPORAL-LOBE EPILEPSY BUT NOT IN ALZHEIMERS-DISEASE

We analyzed hippocampal volumes and T-2 relaxation times by MRI fr om 78 control subjects, 24 patients with temporal lobe epilepsy, and 55 p atients with Alzheimer's disease (AD). In the epilepsy group, the hipp ocampal volumes were 27% smaller than in control subjects (p < 0.001). The T-2 relaxation times were prolonged (8 to 20 ms compared with con trol subjects) in the head, body, and tail portions of the hippocampus on the focal side (p < 0.01) and also on the contralateral side (p < 0.05) compared with control subjects. In the epilepsy group, the prolo ngation of T-2 relaxation time correlated inversely with the hippocamp al volume (p < 0.06). In the AD group, the hippocampal volumes were 35 % smaller than in control subjects (p < 0.01). The T-2 relaxation time s were slightly prolonged (5 to 6 ms) in the head and tail portions of the fight hippocampus (p < 0.01:), but the T-2 relaxation times did n ot correlate with the hippocampal volumes. These data show that the de gree of prolongation of T-2 relaxation time is associated with severit y of hippocampal atrophy in temporal lobe epilepsy but not in AD.