Severity of hippocampal atrophy correlates with the prolongation of MRI T-2 relaxation in temporal lobe epilepsy but not in Alzheimer's 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 patients with Alzheimer's disease (AD). In the epilepsy group, the hippocampal volumes were 27% smaller than in control subjects (p < 0.001). The T-2 relaxation times were prolonged (8 to 20 ms compared with control 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 prolongation of T-2 relaxation time correlated inversely with the hippocampal 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 times 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 not correlate with the hippocampal volumes. These data show that the degree of prolongation of T-2 relaxation time is associated with severity of hippocampal atrophy in temporal lobe epilepsy but not in AD.