Subcortical Gray Matter Volume Abnormalities in Temporal Lobe Epilepsy with Hippocampal Atrophy

Objective: Hippocampal atrophy (HA), the main lesion associated with drug-resistant temporal lobe epilepsy, can be reliably evaluated using conventional magnetic resonance imaging (MRI) with satisfactory lateralization of the epileptogenic focus. Post-processing quantitative techniques permit better evaluation of extratemporal volume abnormalities, including cortical and subcortical gray matter (GM) structures, with more consistent findings in the hemisphere ipsilateral to the epileptogenic focus, including the thalamus and adjacent gyri. We aimed to analyze the relationship between subcortical GM volume and temporal lobe epilepsy associated with hippocampal atrophy (TLE-HA), including hippocampal subfield analysis.Design: A transversal observational study conducted with patients from Clinics Hospital of the Federal University of Paraná, and a group control of healthy participants from Diagnostico Avançado por Imagem - DAPI.Setting: This study was conducted at Diagnostico Avançado por Imagem (Clinical Imaging Institution in Curitiba, Brazil) and Clinics Hospital of the Federal University of Paraná, Brazil.Participants: Patients with TLE-HA referred for surgical planning between September 2013 and August 2018 and individuals without pathologies on MRI scans other than HA were included.Methods: Subcortical GM volumes of the hippocampus, amygdala, and basal ganglia were obtained using automated techniques from the MRI scans of 38 patients with TLE-HA (17 with left TLE-HA) and compared with those of 59 healthy controls.Results: Patients with right TLE-HA demonstrated no significantly lower volumes in the subcortical structures; however, contralateral amygdala enlargement was observed (t = 3.802, P < 0.001). No significant volume loss was observed in the left TLE-HA group, the contralateral hippocampus, or hippocampal subfield comparisons; however, enlargement of the contralateral hippocampal amygdala transitional area was observed (t = 2.57, P = 0.012 for R-TLE-HA; t = 2.20, P = 0.031 for L-TLE-HA).Conclusion: Our findings suggest different patterns of subcortical volume abnormalities in patients with left and right TLE-HA, which may indicate different neural network abnormalities on the ictal side. No significant volume abnormalities existed in the contralateral hippocampus in the TLE-HA group or specific hippocampal subfields in automated analysis. Subtle contralateral amygdala enlargement was present in both groups and may play a specific role in the epileptogenic mechanisms.