[Executive function impairment in patients with temporal lobe epilepsy: neuropsychological and diffusion-tensor imaging study]

Abstract

Objective: To explore the cognitive changes and the relation with the parameters of DTI in the brain areas in patients with temporal lobe epilepsy by neuropsychological test and DTI study.

Methods: Thirty-two patients with temporal lobe epilepsy, 11 males and 8 females, aged 32 +/- 12, with the education year of 8.6 +/- 1.2, and 42 sex, age, and education level-matched healthy controls underwent and a comprehensive test battery test including verbal fluency (VI), digit span (DSp), digit symbol (DSy), Stroop color-word test, trail making test, and so as to evaluate the intelligence level. Nineteen patients and twenty-one control subjects underwent diffusion tensor imaging (DTI) of the head. The correlation between the results of DTI and cognitive function tests of the patients was analyzed.

Results: VI test showed that the number of word spoken in 1 min by the healthy control group was (16 +/- 4), significantly more than that of the patient group [(11 +/- 4), P = 0.00]. The DSp score of the control group was (14.6 +/- 3.1) points, significantly more than that of the patient group [(11.1 +/- 2.8), P = 0.00]. The number of DSy filled by the patient group was (47 +/- 17), significantly less than that of the control group [(60 +/- 16), P = 0.00]. The time needed to make trail of the patients was (56 +/- 20) s, significantly longer than that of the control group [(37 +/- 11) s, P = 0.01]. The Stroop reaction time of the patient group was (6.1 +/- 4.5) s, significantly longer than that of the control group [(30 +/- 5) s, P = 0.00]. The Stroop error number of the patient group was (6.1 +/- 4.5), significantly more than that of the control group [(1.4 +/- 1.2), P = 0.00]. The fractional anisotropy (FA) values of the posterior limb of left internal capsule and of the bilateral thalami of the patient group were significantly lower than those of the control group (P = 0.01 or P = 0.00). VI was negatively correlated with the mean diffusivity (MD) in left caudamen (r = -0.56, P = 0.04), right putamen (r = -0.58, P = 0.04), left putamen (r = -0.58, P = 0.04), and right thalamus (r = -0.64, P = 0.02), and was positively correlated with the FA in white matter of left frontal lobe (r = 0.43, P = 0.04)and left occipital lobe (r = 0.47, P = 0.02). DSp was negatively correlated with the MD in splenium of corpus callosum (r = 0.58, P = 0.04) and left putamen (r = -0.59, P = 0.04). TMT was positively correlated with the MD in the posterior limb of right internal capsule (r = 0.65, P = 0.02) and posterior limb of left internal capsule (r = 0.59, P = 0.03).

Conclusion: The prefrontal cortex is a vital component of the circuitry subserving executive function. But the corresponding damaged area in patients with impaired executive function was not limited to frontal lobe,more areas beyond frontal lobe may be involved in executive function.