Abstracts

Rationale: Executive dysfunction has been recognized in epilepsy associated with mesial temporal sclerosis (MTS). The anatomic correlate underlying executive dysfunction in this setting remains poorly understood, since the hippocampal lesion is not traditionally implicated in the attentional-executive network. We evaluated the association between white matter tract disruption and executive dysfunction evaluated with Stroop 3 in patients with epilepsy associated with unilateral mesial temporal sclerosis (uMTS). Methods: Fifty-one patients with uMTS and 40 healthy controls (HC) underwent a neuropsychological battery, including the Stroop 3 test. Individual patient's performance on Stroop 3 was classified as normal or abnormal based on cut-off scores obtained with the ROC curve (patients vs. HC), using Youdens index. Fifty-one patients and 30 neuroimaging controls (NIC) underwent Diffusion Tensor Imaging studies on a 3T MRI scanner, that were post-processed with the tract-based spatial statistics (TBSS) software. Fractional anisotropy (FA) values for 18 white matter tracts were compared among patients with normal (NL) and impaired (IMP) performance on Stroop 3, and imaging controls (NIC). Results: 51 patients with uMTS, 28 (54.9%) women, 29 (56,9%) left MTS, age 34.0+/-9.3 years, range 19-54, education 10.7+/-1.9 years, range 8-15, age at epilepsy onset 12.7+/-6.7 years, range 0-30, epilepsy duration 22.5+/-9.7 years and mean monthly seizure frequency 7.1+/-, range 1-30 seizures/month. Patients disclosed impaired perfomance on Stroop 3 compared to HC (patients: 33.7+/-13.0 vs. HC 25.5+/-8.6, p < 0.001). IMP patients (n=32) disclosed reduced FA compared to NL patients (n=19) in an extensive white matter tract network, involving the right (p=0.003) and left (p=0.01) anterior thalamic tracts, temporal-frontal connections [left (p=0.03) and right (p=0.002) uncinate fasciculus, right cingulus (p=0.032) , left (0.047) and right (0.046) superior longitudinal fasciculus, including the temporal portion on the right (p=0.039)], temporal-occipital (right inferior longitudinal fasciculus (p=0.027) and left (p=0.033) and right (p=0.011) frontal-occipital connections, as well as interhemispheric connections [minor (p=0.0060 and major fornices (p=0.035)]. Conclusions: Executive dysfunction evaluated with Stroop 3 was associated with bilateral (more pronounced right hemispheric) involvement of an extensive temporal-frontal, thalamo-frontal, temporal-occipital, frontal-occipital, as well as interhemispheric white matter tract network. Extensive white matter tract disruption involving temporal-frontal, limbic and hemispheric connections may play a role in executive dysfunction in temporal lobe epilepsy associated with MTS. Funding: Fundação de Amparo à Pesquisa do Estado de São Paulo - CinaPCe project (num 2005/56464-9), Bolsa de Iniciação científica (G.E.R., num 2014/13626-8)