Effects of white matter microstructure lesions on language and memory function in magnetic resonance imaging-negative temporal lobe epilepsy determined by diffusion tensor imaging.

OBJECTIVES: This study was conducted to investigate the associations between white matter lesions and language and memory dysfunctions in patients with magnetic resonance imaging (MRI)-negative temporal lobe epilepsy.

MATERIALS AND METHODS: This study included 26 patients with temporal lobe epilepsy, who did not have significant findings on conventional MRI scanning, and 17 healthy subjects as control. Diffusion tensor imaging data was obtained with a 3Tesla (T) MRI scanner. Neuropsychological scores of language and memory functions were measured. One-way analysis of variance was used to analyze abnormal fractional anisotropy and mean diffusivity values. Correlations were performed to evaluate the relationship between fractional anisotropy/mean diffusivity of each fiber tract and neuropsychological measures. Regression analysis was performed to determine the contribution of each fiber tract to cognitive performance.

RESULTS: Our data showed significantly decreased neuropsychological scores in the left and right temporal lobe epilepsy groups compared with control; it however, failed to show a statistical difference between the two groups. For the left temporal lobe epilepsy group, the mean diffusivity of the left parahippocampal and cingulate cortex, right arcuate fasciculus, and left fornix were significantly higher than control. Fractional anisotropy of the right fornix and mean diffusivity of the left uncinate fasciculus were significantly related to confrontational naming scores. There were significant correlations between the fractional anisotropy of the left fornix and verbal delayed memory scores and between the fractional anisotropy of the left fornix and nonverbal delayed memory scores. The mean diffusivity of left fractional anisotropy and the fractional anisotropy of the left uncinate fasciculus were significantly related to confrontational naming and verbal fluency scores, and seizure frequency was significantly related to nonverbal delayed memory scores.

CONCLUSIONS: Language and memory function impairment was correlated with white matter structural integrity.