Hippocampal sclerosis: a pathological study of 45 Thai patients using modified blumke classification

Abstract

Hippocampal sclerosis (HS) constitutes the majority of cases undergoing epilepsy surgery, and the recent classification by Blumke in 2007 has shown to predict post-operative outcome. According to the scheme, neuronal density in the hippocampal subfields was compared between case and control, and HS was classified into 4 types: 0, no neuronal loss; 1a, neuronal loss in CA1, CA3, CA4; 1b, neuronal loss in all CA regions; 2, neuronal loss in CA1; and 3, neuronal loss in CA4. In the present study, neuronal density was evaluated with NeuN immunostain performed on normal hippocampi and HS samples. With the normal reference values, neuronal loss in each hippocampal subfield was considered when Z score was less than -1. Of the 45 HS specimens studied, there were 18 cases of type 1a, 2 cases of 1b, and 25 cases of unclassified type 1 HS due to an absence of CA2 in the tissue samples. The lack of other HS types (0, 2 and 3) in our cohort might be due to surgery that selectively performed in patients with expected good outcome (type 1 HS). For the complete classification of HS, CA2 is crucial to separate types 1a and 1b.