TEMPORAL-LOBE EPILEPSY - THE VARIOUS MR APPEARANCES OF HISTOLOGICALLYPROVEN MESIAL TEMPORAL SCLEROSIS

PURPOSE: To determine the frequency of appearance of various MR signs in mesial temporal sclerosis, to determine the optimal scanning planes for their visualization, and to propose a histologic explanation for the diminished demarcation between gray and white matter in the tempor al lobe, a frequent MR finding in patients with mesial temporal sclero sis. METHODS: MR scans of 14 surgically treated patients with epilepsy and histologically proven mesial temporal sclerosis were assessed for the presence of six features: feature 1, high signal intensity in the hippocampus; 2, reduced hippocampal size; 3, ipsilateral atrophy of t he hippocampal collateral white matter; 4, enlarged temporal horn; 5, reduced gray-white matter demarcation in the temporal lobe; and 6, dec reased temporal lobe size. RESULTS: Feature 1 was present in 14 patien ts and was best appreciated on the T2-weighted images in planes parall el to the long axes of the hippocampi. Feature 2, present in 12 patien ts, and feature 6, present in 9 patients, were optimally seen in the c oronal planes and on the inversion-recovery sequences in particular. F eature 3, present in 12 patients, was optimally seen on the coronal T2 -weighted images. Feature 4, seen in 11 patients, was equally well see n in all planes (transverse, coronal, and parallel to the long axes of the hippocampi). Feature 5, seen in 10 patients, was best appreciated on the T2-weighted images in the planes of the long axes of the hippo campi. Histologic investigation of the temporal lobe white matter in t he 10 patients with feature 5 demonstrated on the MR scan showed abnor malities in 7 cases. Oligodendroglia cell clusters were found in 6, wi th concomitant corpora amylacea in 1 case and perivascular macrophages with pigment a sole finding in another case. CONCLUSION: Of the six f eatures found in cases of mesial temporal sclerosis on MR, increased h ippocampal signal intensity is the most consistent. A decreased gray-w hite matter demarcation in the temporal lobe parenchyma is also a freq uent feature of this disease. A combination of multiple scanning plane s results in an optimal demonstration of lesions.