LOSS OF DIGITATIONS OF THE HIPPOCAMPAL HEAD ON HIGH-RESOLUTION FAST SPIN-ECHO MR - A SIGN OF MESIAL TEMPORAL SCLEROSIS

PURPOSE: The purpose of our study was to determine the significance of the loss of visualization of digitations in the hippocampal head on h igh-resolution fast spin-echo MR images in the diagnosis of mesial tem poral sclerosis (MTS), METHODS: MR examinations of 193 patients with i ntractable epilepsy were evaluated retrospectively for atrophy and/or T2 signal changes of the hippocampi, On the basis of these two criteri a, MTS was diagnosed in 63 hippocampi, Twenty-four patients had surger y, and MTS was confirmed in all cases, A control group included 60 hip pocampi in patients with frontal seizures but no MR-detectable abnorma lities, In a second step, visibility of digitations in the hippocampal head was evaluated in the two groups of subjects, RESULTS: In the gro up of 63 hippocampi in which MTS was diagnosed, digitations were not v isible in 51 cases, poorly visible in eight, and sharply visible in fo ur, Twenty-two of 24 hippocampi in which MTS was confirmed histologica lly had no MR-visible digitations. In the control group, digitations w ere sharply visible in 55 cases and poorly visible in five, Statistica l analysis showed a significant difference in the visualization of dig itations between hippocampi ,vith MTS and those in the control group, CONCLUSION: With a sensitivity of 92% and a specificity of 100%, the f inding of complete loss of digitations in the hippocampal head may be used as a major diagnostic criterion to establish the MR diagnosis of MTS, This morphologic sign may also be useful in the diagnosis of bila teral MTS or to validate the MR diagnosis of MTS when there is no obvi ous atrophy or changes in signal intensity.