Do Hippocampal Neurons Really Count for Comorbid Depression in Patients With Mesial Temporal Lobe Epilepsy and Hippocampal Sclerosis? A Histopathological Study.

Nathália Stela Visoná De Figueiredo,Maria Helena Da Silva Noffs,Neide Barreira Alonso,Ricardo Silva Centeno,Carla Alessandra Scorza,Lenon Mazetto,Anaclara Prada Jardim,Elza Márcia Targas Yacubian,Jeana Torres Corso Duarte,Esper Abrão Cavalheiro,Sandra Mara Comper,Gerardo Maria De Araújo Filho

doi:10.3389/fnint.2021.747237

Abstract

Depression is the most frequent psychiatric comorbidity seen in mesial temporal lobe epilepsy (MTLE) patients with hippocampal sclerosis (HS). Moreover, the HS is the most frequent pathological hallmark in MTLE-HS. Although there is a well-documented hippocampal volumetric reduction in imaging studies of patients with major depressive disorder, in epilepsy with comorbid depression, the true role of the hippocampus is not entirely understood. This study aimed to verify if patients with unilateral MTLE-HS and the co-occurrence of depression have differences in neuronal density of the hippocampal sectors CA1–CA4. For this purpose, we used a histopathological approach. This was a pioneering study with patients having both clinical disorders. However, we found no difference in hippocampal neuronal density when depression co-occurs in patients with epilepsy. In this series, CA1 had the lowest counting in both groups, and HS ILAE Type 1 was the most prevalent. More studies using histological assessments are needed to clarify the physiopathology of depression in MTLE-HS.

Highlights

Significant attention has been paid to comorbidities in epilepsy as they have important implications in the quality of life of patients
This clinical situation occurs in mesial temporal lobe epilepsy (MTLE) with hippocampal sclerosis (HS), which frequently leads to surgical treatment (Blümcke et al, 2002)
This study aimed to evaluate the aspects related to the histopathology of the hippocampus obtained after epilepsy surgery in a series of patients with MTLE-HS, comparing cases with vs. without comorbid depression

Summary

Introduction

Significant attention has been paid to comorbidities in epilepsy as they have important implications in the quality of life of patients. Psychiatric comorbidities are found in this context, and depression is the most prevalent (Hermann et al, 2000), occurring in approximately 22.9% of people with epilepsy (PWE) (Scott et al, 2017). It can be clinically relevant in about 30–50% of patients with drug-resistant epilepsies throughout their lifetime (Gilliam and Kanner, 2002; Nogueira et al, 2017). This clinical situation occurs in mesial temporal lobe epilepsy (MTLE) with hippocampal sclerosis (HS), which frequently leads to surgical treatment (Blümcke et al, 2002). In relation to the hippocampal sectors, moderate cellular apoptosis in CA1 and CA4 was reported in post-mortem studies of patients with this psychiatric disorder (Lucassen et al, 2001)

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