Regional distribution of MR findings in hippocampal sclerosis.

PURPOSE To investigate the distribution of MR findings in the hippocampus and amygdala in patients with hippocampal sclerosis.

METHODS We blindly evaluated MR scans for atrophy and signal changes occurring in the amygdala, hippocampal head, hippocampal body, and hippocampal tail in 57 consecutive patients with hippocampal sclerosis proved by pathologic analysis.

RESULTS Regional atrophy or signal change was present in limbic structures. Atrophy was detected in 52 patients, occurring in the amygdala in 7 (12%), hippocampal head in 29 (51%), hippocampal body in 50 (88%), and hippocampal tail in 35 (61%). Hyperintense signal on long-repetition-time images was observed in 49 patients and involved the amygdala in 2 (4%), hippocampal head in 22 (39%), hippocampal body in 46 (81%), and hippocampal tail in 28 (49%). Thirty patients (53%) had abnormal MR findings distributed through the entire ipsilateral hippocampus, 25 (44%) had regional rather than widespread involvement of limbic structures, and 2 (3%) had no MR abnormalities.

CONCLUSION Signal and volume changes associated with hippocampal sclerosis affect the entire hippocampus in most patients. However, a substantial number of patients have MR abnormalities that are regional, involving only portions of the hippocampus and amygdala. The most frequently affected region was the hippocampal body. These findings can have important implications for surgery and quantitative image analysis, if the seizure generator is related to MR changes.