Quantitative neuropathology and quantitative magnetic resonance imaging of the hippocampus in temporal lobe epilepsy

The aims of this study were to examine the relationships of hippocampal T2 (HCT2) relaxation time and magnetic resonance (MR)-based hippocampal volume (HCV) to neuronal (ND) and glial cell densities (GD) of hippocampal neuronal cell layers, and to obtain a better clinicopathological definition of hippocampal sclerosis (HS) and end folium sclerosis (EFS). Fifty-three hippocampi with HS, 6 with EFS, and 6 control hippocampi were studied. Pathologically, the HS group had a significantly higher logarithm (log) GD/ND than the controls in all hippocampal subregions, and than the EFS group in all subregions except the granule cell layer of the dentate gyrus (GCDG). The EFS group had a significantly higher log GD/ND than the control group only in the GCDG. Clinical correlations suggested that EFS may be the consequence of temporal lobe seizures and not an epileptogenic entity. Hippocampal atrophy in HS was associated with neuronal cell depletion and concomitant gliosis in the cornu Ammonis (CA) 1, CA2, CA3, and hilus. An increased HCT2 was associated with damage in the CA1 and also the hilus and has a different neuropathological basis than HCV loss. MR-based HCV measurement and HCT2 mapping, therefore, give complementary information in the presurgical evaluation of temporal lobe epilepsy and longitudinal studies.