Abstracts

Rationale: Gray matter (GM) concentration decrease of hippocampus and ipsilateral thalamus is a consistent structural change observed in voxel-based morphometry (VBM) studies on temporal lobe epilepsy with hippocampal sclerosis (TLE-HS). This is an expected finding since these structures are functionally co-activated and participate in the same network of neurons (Barron et al., 2013). Few studies address the association between frontal lobe -related cognitive functions and GM abnormalities. Herein, we aimed to evaluate the correlation between GM concentration and executive/attentional impairment in patients with TLE-HS.Methods: We evaluated 32 patients with refractory TLE-HS (71.9% women, mean age 36.9 y [SD 13.9]), 10 yrs of education (SD 3.01) and estimated IQ of 91.7 (SD:13.5). The group of 31 controls were matched for age(p 0.093) and gender (p 0.528). Patients had a lower number of schooling (p 0.003) and lower IQ (p 0.001).Patients and controls underwent a two stage study with clinical and VBM phase. In the first, we studied the executive/attentional performance with a comprehensive neuropsychological battery. In the second, we evaluated the correlation between the GM concentration with those executive/attentional that patients had worse performance. Performances’ comparison was done using ANCOVA, using educational level as a covariant.Results: Patients with TLE-HS had worse performance on TMTA time (F=6.75, p=0.013) and B time (F=6.00, p=0.018), and CPT-II (omissions: F=6.16, p=0.017; variability:F=5.41, p=0.025 CPT TR isi: F=4.30, p=0.044; detectability: F=4.12, p=0.048 ). A trend was observed for WCST number of perseverative responses (F=3.39, p=0.072) and Verbal Fluency (category for animals - F=2,96, p=0,092). There was a correlation between the decrease of GM concentration in Dorsolateral Prefrontal Cortex and worse performance in TMT A e B (Z=4,21; pFWE=0,037; Z=4,22; pFWE=0,018 respectively). (Fig 1) Decrease on Hippocampal concentration (Z=3,57; pFWE=0,029 ), Insula (Z=4,02; pFWE=0,013 ) and right/left Parahippocampal Gyrus (Z=3,69; pFWE=0,022 and Z=3,95, pFWE=0,007 ) were associated with worse performance in CPT. WCST and Verbal Fluency were not significantly associated to GM volume decrease.Conclusions: This study demonstrated the association between dorsolateral prefrontal cortex and complex attentional processes. To our knowledge, this is the first study showing that the relevance of dorsolateral prefrontal cortex on alternating attention is not restricted to prefrontal lobe lesions, but also in TLE-HS. It suggests that the presence of a temporal lobe lesion can modify the connectivity between different regions. This work also corroborates the role of hippocampus on attentional processes and inhibitory control, as previously shown in experimental and clinical studies, but not in TLE-HS.