To evaluate white-matter (WM) tract integrity in Temporal Lobe Epilepsy and Hippocampal Sclerosis (TLE-HS) patients with verbal-memory impairment (VMI).

TLE-HS patients frequently display VMI. While VMI has been associated with HS, the association of white-matter tract involvement in VMI, remains poorly characterized.

We studied 50 unilateral TLE-HS patients aged 17-55, education >=8 years, IQ >=70, with exclusive temporal discharges on EEG. Patients on topiramate or active psychiatric disease were excluded. Participants and healthy controls fulfilling the same criteria underwent the Logical Memory test (LMT) and Rey Auditory Verbal Learning Test (RAVLT). Patients were classified as impaired VM, if performance was below minus 1.5 SDs of controls. Patients underwent 3T-MRI with DTI. Voxel-wise fractional anisotropy (FA) was compared between normal and VMI groups using TBSS-FSL.

50 patients underwent RAVLT and 48 underwent LMT. Epilepsy duration, seizure frequency, and antiseizure medication load did not differ between normal and impaired VM groups. TBSS revealed significant differences in WM integrity between patients with poor and normal performance in the LMT and RAVLT tests. Compared to patients with normal VM, patients with poor performance in the LMT, displayed decreased FA in the left corticospinal tract, superior longitudinal fasciculus, corpus callosum, forceps major, anterior thalamic radiation, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus and uncinate fasciculus. Patients who performed worse in the RAVLT had more diffuse WM damage compared to patients with preserved RAVLT VM performance. In comparison with controls, both patient groups, regardless of performance, showed diffusely decreased FA.

In TLE-HS patients, VMI is associated with widespread temporal and extratemporal WM involvement. In addition to the hippocampal lesion, white matter tract involvement may contribute to memory dysfunction in TLE-HS.