Alteration Of Visual Structure In Patients With Relapsing Remitting Multiple Sclerosis: A Functional And Structural Magnetic Resonance Imaging Study

Objective: Functional magnetic resonance imaging technologies includingfunctional connectivity MRI (fcMRI), and diffusion tensor imaging-fibertractography (DTI-FT) were used to analyze resting-state functional connectivity inprimary visual cortex (V1)and structural connectivity in primary visual cortex andoptic radiation in patients with relapsing-remitting multiple sclerosis (RRMS) andhealthy subjects so as to explore characteristic functional and structural changes intissue related to visual function in patients with RRMS as well as the relationshipbetween these two changes.Methods:20cases of RRMS patients clinically diagnosed and20healthyvolunteers with sex, age and education level matched from June2011–December2013were performed by3.0T MRI brain scan to acquire conventional image usedfor imaging diagnosis and functional data including blood oxygen level dependentsignal and diffusion tensor imaging for processing. Disease duration and clinicaloutcome parameters with expanded disability status scale, paced auditory serialaddition test and modified fatigue impact scale in RRMS were recorded. Datapre-processing and post-processing was conducted by some software such asDPARSF, SPM8, REST, TrackVis, DTI-Studio and so on,to acquire functionalconnectivity strength in V1as well as DTI parameter values including fractionalanisotropy (FA), apparent diffusion coefficient (ADC), λ∥and λ⊥values) in V1andoptic radiation(OR) in RRMS group and healthy controls(HCs) These resultingvalues were statistically analyzed.Results:1. MFIS and EDSS scores in RRMS group were higher than that in HCs,PASAT score lower than that in the control group.2. Compared with HCs, decreased FC presented between the V1and the right inferiorparietal lobule（brodmann’s area40，BA40）, the right middle frontal gyrus（BA46）and the right cerebellum. Increased FC was found between V1and the anteriorcingulate gyrus（BA32）in RRMS group.(P <0.05). 3. Compared with HCs，RRMS groups exhibited a significantly increased ADC（t=3.056，P=0.004）,λ∥（t=2.523,P=0.016）,and λ⊥（t=2.523,P=0.005）values in the V1,but it was not statistically decreased in FA values. Significantlydecreased FAvalues （t=-2.405, P=0.021）were detected in OR.4. There were positively correlations between some values including ADC（r=0.539, P=0.014）,λ∥（r=0.514，P=0.020）and λ⊥（r=0.497, P=0.026）valuesand disease duration in the V1. The FA value has no correlation between the V1andthe OR.5. The functional connectivity strength in right frontal brain regions and λ⊥values in V1in RRMS group were negatively correlated (r=-0.453, P=0.045).Thatin the right cerebellar hemisphere andλ∥(r=0.551, P=0.012), λ⊥(r=0.513, P=0.021) as well asADC values (r=0.559, P=0.010) in V1have positive correlation.Conclusion:1. RRMS patients present abnormal functional connectivity and structure in V1,which may have correlation with potentially visuospatial working memorydysfunction.2. RRMS patients present structural damage in V1and OR; Extent of damage ofthe two structure has not correlation, which suggests that the pathological changebetween the two structure may occur independently.3. In RRMS patients the disease duration is longer, the micro-structure of V1presents more obvious damage. Structural changes in primary visual cortex mayaffect the abnormal functional connectivity of primary visual cortex.