The Study Of MR Diffusion Tensor Imaging And The Cognitive Impairment In Patients With Periventricular White Matter Lesions

Backgrounds and Objectives: Cerebral white matter disease is a kind of structuralchanges in brain, which is characterized by the myelin damage of the central nervous cells.Cerebral white matter lesions (WML) mainly involve the white matter tracts of higher brainfunction in the periventricular and semi ovalregion. Cerebral white matter lesions can bedivided into periventricular white matter lesions and deep white matter lesions. Thepathological mechanisms and risk factors for the two types of white matter lesions may bedifferent, but most studies support the hypothesis of chronic ischemic injury, which is thatcerebral sclerosis of small blood vessels lead to chronic ischemic white matter, leadingto loss of myelin sheath and glial hyperplasia. With the wide application of magneticresonance imaging (MRI), different degree of WMLs can be seen in the brain of more thanhalf of the elderly through the MRI examination, which was used to think as a normalphysiological process. Cognitive dyfunction are a category of mental health disorders thatprimarily affect learning, memory, perception, and problem solving, and include amnesia,dementia, and delirium. With the increase of age, the incidence and prevalence rate ofcognitive decline significantly increased. Recently, however, there have been a largenumber of domestic and foreign studies showed that the cerebral white matter degenerationis an important risk factor for dementia, even may be the direct cause of dementia.Although it has been reported that the cerebral white matter lesions are associated with thespecific aspects of cognitive impairment, the pathological mechanism by which cerebralwhite matter lesions lead to cognitive impairment is unclear. Further researches arenecessary to carry out. Therefore, the purpose of this study is to investigatethe characteristics of cognitive impairment and the association between cognitiveimpairment and specific white matter fiber damage, so as to further understand thepathological mechanisms by which white matter lesions lead to cognitive impairment. Methods: Patients with periventricular white matter lesions on MRI were enrolled inthe present study. We evaluate the cognitive impairments with neuropsychological scaleand individual cognition scale, evaluate the damage of white matter fiber beam withmagnetic resonance diffusion tensor imaging technology, and evaluate the changes ofCortical structure with Surface Based Morphometry (SBM) technology, evaluate thepossible factors which are associated with the cognitive impairments by univariate analysis,then evaluate the relationship among white matter fiber tracts injury, cortical thickness, andcognitive impairments with Univariate and Multivariate correlation analysis.Results: Compared with the normal control group, we found that the cognitive tests ofpatients with periventricular white matter lesions showed significant decline in the domainsof verbal fluency and executive function; DTI measurements showed a significantinter-group difference with decreased FA in the bilateral anterior,posterior periventricularwhite matter and genu;Cortical thickness measurements showed significant corticalthinning in the frontal pole, orbital frontal gyrus, superior frontal gyrus, middle frontalgyrus, the insula and cuneus. Univariate analysis showed that age was inversely related toexecutive function; years of education was positively related to verbal fluency and attention,women had lower scores than men on attention and verbal fluency test;Additionally,participants with hypertension had lower scores of verbal fluency test and smoker hadlower scores of verbal memory test;The FA of both anterior and posterior PWM wasinversely associated with the test of executive function; FA of bilateral posterior PWM andgenu was positively associated with the test of verbal fluency; The cortical thickness in thefrontal pole, the superior and middle frontal gyrus, the orbitofrontal gyrus, the superior andmiddle temporal gyrus, the insula and the lingual and cuneus gyrus of the bilateralhemisphere were inversely correlated with the test of executive function in the subjects withPWMHS;The cortical thickness in the middle frontal gyrus, the superior and middletemporal gyrus, and the lingual and cuneus gyrus of the bilateral hemisphere and the rightorbitofrontal gyrus was positively correlated with the test of verbal fluency;The corticalthickness in the right middle frontal gyrus and the superior temporal gyrus were positivelycorrelated with the test of visuospatial skill in the subjects with PWMHS; The corticalthickness in the the middle frontal gyrus, the superior and middle temporal gyrus, the insulagyrus of the bilateral hemisphere were positively correlated with the test of verbal memory in the subjects with PWMHS.After accounting for the factors of age, gender, years ofeducation, hypertension, hyperlipemia, diabetes mellitus and smoking, DTI measurementsof white matter fiber tracts injury were no longer correlated with the cognitive test scoreswhen the factor of cortical thickness was added, whereas the cortical thickness had anindependent influence on the cognitive impairments. We found that the cortical thickness inthe frontal pole, the superior and middle frontal gyrus, the orbitofrontal gyrus, the insulagyrus of the bilateral hemisphere was inversely correlated with the test of executivefunction. The cortical thickness in the middle frontal gyrus, the superior and middletemporal gyrus, and the cuneus gyrus of the bilateral hemisphere, and the right orbitofrontalgyrus were positively correlated with the test of verbal fluency.Conclusions: The cognitive tests of patients with periventricular white matter lesionsshowed significant decline in the domains of verbal fluency and executive function. Ourresults suggest that the association between the damage of white matter fiber tracts andcognitive impairments is mediated by cortical thinning.