Neural correlates of de novo depression following left temporal lobe epilepsy surgery: A voxel based morphometry study of pre-surgical structural MRI

Purpose: To investigate cerebral grey matter (GM) volumetric abnormalities in temporal lobe epilepsy (TLE) patients who develop de novo depression following TLE surgery using voxel-based morphometry (VBM). Methods: We retrospectively examined pre-surgical grey matter (GM) volumes in 30 patients with TLE due to unilateral left-sided hippocampal sclerosis using 1.5-T MRI scan, which were segmented with optimised VBM parameters and normalised to a sample template using DARTEL, with SPM8 software. Voxel-wise GM differences between patients that developed de novo post-surgical depression (n=5) were compared with patients with no pre- or postoperative psychiatric diagnoses (n=25), using independent samples t-tests with age, gender and secondary generalised tonic clonic seizures (SGTCS) as covariates (p<.001, unc). Key findings: Reduced preoperative bilateral GM in orbitofrontal cortices (OFC) and ipsilateral cingulate gyrus and thalamus were significantly associated with the development of de novo depression within 4 years postoperatively. Further analyses revealed no differences in seizure freedom (LAE 1 vs 2-6) or postoperative memory decline between the groups. Significance: Although the development of postoperative de novo depression following TLE surgery is likely to be multi-factorial, our results suggest that bilateral OFC and ipsilateral cingulate gyrus and thalamic atrophy in left-sided TLE patients may play a modulatory role. Abnormalities in these areas have also been implicated in primary mood disorders. Prospective neuroimaging studies with larger cohorts are warranted to replicate these results, and further elucidate the neural correlates of de novo depression. (C) 2014 Elsevier B.V. All rights reserved.