Longitudinal variation in cell density and mossy fiber reorganization in the dentate gyrus from temporal lobe epileptic patients

Abstract

Variation in cell loss and mossy fiber reorganization was examined along the longitudinal axis of the dentate gyrus from temporal lobe epileptic (TLE) patients. Previous evidence has indicated that the anterior hippocampus is prone to seizure activity. We compared granule and hilar cell number in addition to Timm stain density of the molecular layer and hilus in more anterior and more posterior specimens of hippocampus obtained from patients surgically treated for intractable epilepsy by the removal of the anterior half of the hippocampus. Granule cells/mm in the more anterior specimen were less than or equal to those in the more posterior specimen locations in 77% of the patients, while there was no significant difference in hilar neuron density between the two blocks. These results demonstrate a significantly greater pathology in the granule cell layer in more anterior specimens and no difference in pathology for hilar neurons. Molecular layer Timm stain density was significantly greater in the more anterior specimen of 71% of the patients. The molecular layer Timm stain density ratio was inversely related to hilar cell density in more anterior specimens, whereas in more posterior specimens there was no significant relationship with hilar cell density. Our observations show that although differences exist among TLE patients for these neuroanatomic measures, pathology was greater in more anterior specimens. The latter result is consistent with the conclusion that seizure activity may originate in the anterior region of the hippocampus in a majority of patients.