Correlation Between Cognitive Impairment And Diffusion Tensor Imaging In Patients With Multiple Sclerosis

Multiple Sclerosis (MS) is an inflammatory, demyelinating and idiopathic disease of the central nervous system and typically affects women, with a peak onset of approximately 33 years of age. The disease usually leads to multiple neurological disabilities, including motor and sensation dysfunction, visual impairment, etc. Prevalence of cognitive impairment in MS varies from 50% to 70% leading to poor quality of life and social burdens. Many factors can influence cognitive function, such as age, course of the disease, clinical subtypes and cognitive reserve, but none can be seen as the specific predictor.The cognitive domains commonly affected in MS include short-term memory, information processing speed, attention, visuo-spatial working memory and executive functioning. The brief repeatable neuropsychological battery (BRB-N) and the minimal assessment of cognitive function in Multiple Sclerosis (MACFIMS) have gained quit wide application in western countries,however, there is no matching Chinese versions in China. What’s more, the complicated operation and longer time needed restrict their application. Therefore, the tests used in this study were simpler but aimed at some specific aspects, and preliminarily analyzed the characteristics of cognitive impairment.In recent years, with the development of radiological technology, studies on pathological changes of MS rise to a new lever. But lesions showed on conventional magnetic resonance imaging (cMRI) aren’t correlated well with patients’ clinical symptoms. Some novel magnetic resonance imaging techniques have a significant advantage on showing lesions related to cognitive impairment, such as magnetization transfer imaging (MTI), diffusion tensor imaging (DTI), magnetic resonance spectroscopy (MRS), functional MRI (fMRI) and double inversion recovery (DIR), which can show the demyelinating lesions more clear and detect occult structural, metabolic and functional changes in normal-appearing brain tissue.In this study, we used DTI to explore whether occult injury exists or not, and analyze its correlation with cognitive function, in order to clarify the underlying mechanism of cognitive impairment in MS.Objective:To investigate the characteristics of cognitive impairment and DTI in MS patients and explore the relevance between neuropsychological test scores and DTI changes.Methods:1.Twenty-three patients with MS and twenty-three age- and sex-matched healthy controls in the department of Neurology or clinic of our hospital since June 2013 to January 2015 were enrolled in the study. All subjects were submitted to a battery of neuropsychological tests to assess general cognitive function,executive function, attention and information processing speed. The neuropsychology tests included mini-mental state examnation (MMSE), montreal cognitive assessment (MoCA), symbol digit modalities test (SDMT), trail making test (TMT) and color word test (CWT).2.Twenty-three patients and twenty-three control subjects underwent tests of traditional magnetic resonance imaging and brain diffusion tensor imaging examination. Correlation analysis were made to clarify the relationship between the score of cognitive tests and apparent diffusion doefficient (ADC) values and fractional anisotropy (FA) values in normal-appearing brain tissue of MS patients, respectively.Results:1. The general cognitive function test showed that the MMSE and MoCA test scores of the MS group were lower than that of the control group (P<0.05), executive function, attention and information processing speed were damaged in MS group. The scores of VFT, DST and SDMT in MS group were lower than that of the control group (P<0.05). The CWT and TMT scores of MS group were higher than that of the control group (P<0.05). SDMT and CWT had correlation with disease duration (r=-0.430 and 0.455, P<0.05). SDMT had negative correlation with EDSS scores (P<0.05).2. Compared with healthy controls, an significant decrease in FA values was identified in normal-appearing white matter (the white matter of frontal and occipital lobe, the splenium of the corpus callosum, and caudate) (P<0.05). FA values of the thalamus was higher in MS patients compared to controls. ADC values in NAWM (the white matter of frontal and occipital lobe, the genu of the corpus callosum, and the thalamus) of MS group was higher than that of the control (P<0.05).3. The test results of cognitive function had significant correlation with the ADC values and FA values of specific parts of brain (P<0.05).The VFT scores had positive correlation with FA values in the occipital white matter and had negative relation with ADC values in the frontal white matter(P<0.05). Stroop-3 had negative relation with FA values of occipital white matter and the splenium of the corpus callosum (P<0.05). Positive correlation between Stroop-3 and ADC values in the occipital white matter and the genu of corpus callosum, negative correlation between DST scores and ADC values in the occipital white matter, negative correlation between SDMT scores and ADC values in thalamus were demonstrated to be of statistic significance by correlation analyse (P<0.05)Conclusion:1. Cognitive function is impaired in MS patients to various degrees, and typically includes the attention, working memory, executive function and information processing speed. Disease duration and EDSS have different influences on them.2. The ADC values and FA values in brain DTI of MS patients can reflect the occult injury in normal-appearing brain tissue, and have correlation with cognitive dysfunction in MS patients.