Abstracts

Rationale: Verbal memory impairment is well recognized in patients with temporal lobe epilepsy (TLE) associated with unilateral hippocampal sclerosis (uHS). Brain volumetric and white matter changes, not restricted to the hippocampus, have been described in TLE. Few studies have evaluated the association between extra-hippocampal volumetric and white matter changes and verbal memory impairment in left uHS. We evaluated the association between verbal memory deficits and MRI volumetric and white matter tract changes in left uHS patients, using 3T-MRI volumetric and diffusion tensor imaging (DTI). Methods: Twenty-nine patients (34.8+/-8.9 years, 55% women) with TLE associated with left uHS and 40 healthy controls (38.9+/-10.8 years, 60% women) underwent the Rey Auditory Verbal Learning Test (RAVLT), with an additional 7-day delayed recall item. We analyzed performance in total learning scores, immediate (RAVLT 6), delayed (RAVLT7), and very late (one week) recall. We used ROC-curve analysis (patients vs. controls) to establish cut-off scores (Youden Index) for each RAVLT item. According to cut-off scores, patients were classified as impaired (IMP) or normal performance (NP) for each RAVLT item. All patients and 30 healthy imaging controls (HIC) underwent a 3T brain MRI, with volumetric and DTI acquisitions. MRI data were post-processed with FreeSurfer and tract based spatial statistics (TBSS), obtaining brain structures volumes and fractional anisotropy (FA) data for 18 white matter tracts. Volumetric data of encephalic structures and FA data were compared among IMP and NP groups and HIC. Results: IMP and NP patients did not differ in age, gender, epilepsy duration or antiepileptic drug load. Patients with verbal memory impairment on RAVLT 6 displayed reduced FA of the contralateral anterior thalamic radiation compared to NP patients (p = 0.023) and to HIC (p < 0.001). IMP patient groups on all RAVLT items showed volumetric reduction in the corpus callosum central portion, and ipsi- and contralateral FA reductions in the uncinate and inferior fronto-occipital fasciculi, as well as in the forceps minor and major compared to controls, but not to NP groups. Additionally, we found reduced volumetric changes in the middle-anterior, middle-posterior and posterior corpus callosum portions, and decreased FA in ipsi- and contralateral inferior longitudinal fasciculi and cingulum (hippocampus and cingulate gyrus portions), as well as in the ipsilateral anterior thalamic radiation in IMP groups with impaired performance in two or three RAVLT items compared to controls, but not in any NP group compared to controls. Conclusions: Interhemispheric, limbic and temporo-frontal white matter tracts changes were associated with impaired verbal memory performance in uHS TLE. These findings suggest a potential role of white matter tract involvement in verbal memory impairment in this patient population. Funding: FAPESP (Funda磯 de Amparo ࠐesquisa do Estado de S㯠Paulo), process 2014/12765-4 FAPESP (Bolsa de Inicia磯 Cient_x005F_xD9A9_ca - CHZM), process 2014/12765-4