A new clinico-pathological classiWcation system for mesial temporal sclerosis

We propose a histopathological classiWcation system for hippocampal cell loss in patients suVering from mesial temporal lobe epilepsies (MTLE). One hundred and seventy-eight surgically resected specimens were microscopically examined with respect to neuronal cell loss in hippocampal subWelds CA1-CA4 and den- tate gyrus. Five distinct patterns were recognized within a consecutive cohort of anatomically well-preserved sur- gical specimens. The Wrst group comprised hippocampi with neuronal cell densities not signiWcantly diVerent from age matched autopsy controls (no mesial temporal sclerosis (no MTS); n = 34, 19%). A classical pattern with severe cell loss in CA1 and moderate neuronal loss in all other subWelds excluding CA2 was observed in 33 cases (19%), whereas the vast majority of cases showed extensive neuronal cell loss in all hippocampal subWelds (n = 94, 53%). Due to considerable similarities of neuro- nal cell loss patterns and clinical histories, we designated these two groups as MTS type 1a and 1b, respectively. We further distinguished two atypical variants charac- terized either by severe neuronal loss restricted to sector CA1 (MTS type 2; n = 10, 6%) or to the hilar region (MTS type 3, n = 7, 4%). Correlation with clinical data pointed to an early age of initial precipitating injury