Cognitive Impairment In Epileptic Patients: Neuropsychological And Diffusion-Tensor Imaging Study

Objectives1 .To study the cognitive impairment and the related factors in patients with epilepsy.2.To explore the pathologic changes in the brain areas corresponding to specific cognitive function and underlying mechanism of cognitive impairment in patients with epilepsy by DTI study.Material and methods1. 109 patients with epilepsy and 75 age-matched healthy controls were recruited in this study, their intelligence level were evaluated by means of Wechsler Adult Intelligence Scale. VIQ,PIQ and FIQ of patients were compared with that of healthy controls by T test, the related factors impact on FIQ was analyzed by multiple linear regression model.2. Patients and control subjects were administered a comprehensive test battery including standard clinical measure of intelligence (MMSE), verbal fluency, executive function(Stroop test), speeded psychomotor processing(Trail making test A), Digit Span and Digit Symbol .The related factors' influence on the executive function in patients with epilepsy were analyzed by means of multiple linear regression model.3. 44 Patients and 20 control subjects were administered a test of Wechsler Adult Intelligence Scale and the Diffusion-Tensor Imaging examination. MD and FA in the normal appearing white matter of interested area were measured. T test was employed to compare the MD and FA between patients and healthy controls, patients with normal and impaired FIQ respectively. The relationships between FIQ and DTI value were analyzed by Bivariate correlations andmultiple linear regression model.4. 44 Patients and 20 control subjects were administered the DTI examination and a comprehensive test battery test including Stroop test, Trail making test A, Digit Span and Digit Symbol . MD and FA in the normal appearing white matter of interested area were measured. T test was employed to compare the MD and FA between the patients with epilepsy and health controls, patients with normal and impaired executive function normal and impairment patients. The relationship between executive function and FA value were analyzed by Bivariate correlations and multiple linear regression model.Results1. VIQ,PIQ and FIQ of the patients with epilepsy were significantly lower than that of health controls. FIQ,PIQ of TLE patients were significantly lower than that of FLE patients. Multiple regression analysis indicated education, temporal lobe epilepsy, and AEDs were significantly associated with FIQ;education, AEDs, duration and age significantly affected VIQ. Education, and temporal lobe epilepsy were significantly associated with PIQ.2 The control group produced significantly more words than the epileptic group(p<0.01). The Digit Span and Digit Symbol of epilepsy group were significantly lower than that of control group.The epileptic group needed significantly more time to accomplish Trail making test. In TLE group, digit span , and MMSE were significantly less than that in FLE group.Multiple linear regression analysis indicated education and temporal lobe epilepsy were associated with verbal fluency;education, AEDs, duration and age were associated with Digit Span.3. Lesions in patients showed both increased diffusivity and decreased anisotropy compared with the normal-appearing white matter.In normal-appearing white matter, similar abnormalities were found compared with the same area of the contralateral. Significant reduction of FA in both side ofposterior limb of internal capsule (p<0.05) were revealed in epileptic group. Significant increase of MD in genu of corpus callosum and significant reduced FA (p<0.05) in both side of anterior limb of interal capsule , genu of left interal capsule , left external capsule ,white matter of both side occiptial lobe and both putamen were demonstrated in patients with impaired cognition compared with those with normal cognition. Positive correlations between FA in right occipital lobe and FIQ,negative correlations between MD value in right frontal lobe and verbal intelligence, positive correlations between FA in right occipital lobe and verbal intelligence, positive correlations between FA value in both occipital lobe and PIQ were discovered .4. Significant increase of MD in right occipital lobe and significant reduced FA (p<0.05) in both occipital lobe, right caudamen and both putamen were demonstrated in patients with impaired influncy compared with those with normal influncy. Positive correlation between verbal fulency and FA in white matter of right occipital lobe , correlation between digit span and MD and FA in white matter of right frontal lobe, negative correlation between MMSE and MD in posterior limb of left internal capsule, positive correlation between MMSE and FA in anterior limb of left internal capsule , left external capsule ,left frontal lobe and occipital lobe were demonstrated to be of satistic significance by multiple linear regression model.Conclusions1. Patients with epilepsy exhibited significant decreased FIQ , PIQ,VIQ and several aspects of executive function. The ability of memory ,constructive integration and spatial abstraction were more severely impaired in TLE patients than that in FLE patients..2. Better education, non-TLE, and non-multiple ADEs treatment were proved to be protective factors of FIQ. Better education, short-duration, and increased age were protective factors of VIQ. Better education and non-TLEwere protective factors of PIQ. Patients received better education also showed better executive function. TLE patients showed impaired verbal fluency. Digit Span and Digit Symbol were affected by duration and lesion visible on imaging study .AEDs siginificantly lengthened stroop reaction time.3. DTI studied revealed increaed MD in genu of corpus callosum and decreased FA in anterior limb of both interal capsule , genu of left interal capsule , left external capsule, white matter of both side occiptial lobe and both putamen in patients with impaired intelligence. The above results indicated that slight pathogic change such as demylination ,axonal damage and gliosis might exist in patients with impaired intelligence,which cann't be found by routine MRI. Decreased fractional Anisotropy in occipital lobe might be associated with impairment of intelligence and increased MD in frontal lobe might be associated with impairment of verbal intelligence which indicated that white matter might play a important role in cognitive function.4. DTI study revealed increased MD in right occipital lobe and significant reduced FA (p<0.05) in both occipital lobe, right caudamen and both putamen. Positive correlation between digit span and MD and FA in white matter of right frontal lobe, correlation between MMSE and posterior limb of left internal capsule, anterior limb of left internal capsule , left external capsule ,left frontal lobe and occipital lobe were demonstrated to be of satistic significance by multiple linear regression model. The above results suggested that corresponding damaged area in patients with impaired verbal fluency was not limited to frontal lobe which was considered as the classic execution center . More areas beyond frontal lobe might participate executive function.