| Objective:Multiple sclerosis is one of the most common chronic inflammatory demyelinating diseases in central nervous system.Conventional magnetic resonance imaging shows that there are multiple white matter hyperintense lesions in the brain,but there also exists occult damage in the normal-appearing white matter and part of gray matter.Tractography basing on diffusion tensor imaging can be used to reconstruct white matter fiber bundles and evaluate the microstructure tissue damage with high sensitivity.The limbic system plays an important role in activities such as learning,memory,and emotion expression,and it is the structure foundation of human brain cognitive function.This study aimed to evaluate the damage of the fiber system of multiple sclerosis limbic system by diffusion tensor imaging tractography.Method:20 RRMS patients(MS group)diagnosed by the Department of Neurology of the First Affiliated Hospital of Chongqing Medical University from June 2014 to March 2016 and 20 healthy volunteers(control group)were recruited.The conventional MRI,DTI and 3D-T1 data and clinic scales scores were acquired.Diffusion parameter maps and fiber maps were generated separately by pre-processing the DTI data with FSL and DTK software.And FSL was used to register all native space maps to the MNI standard space basing on corresponding high-resolution 3D-T1 images.Trackvis software was used to track all subjects’ the main fiber pathways—cingulum,fornix,and uncinate fasciculus(UF)—of the hippocampus-thalamus-frontotemporal lobe circuit in limbic system.The corresponding fiber number,FA value,and MD value were obtained.The differences in each parameter between the two groups and the correlations between MRI parameters and clinic scales scores were both assessed.Results:(1)Compared to control group,lower FA value(all P<0.01)and higher MD value(all P<0.05)were found in cingulum,fornix and UF of MS patients;and the fiber numbers of fornix was decreased in MS patients(P<0.001).(2)There were no statistically significant differences between left and right hemisphere in the parameters of cingulum and fornix in all subjects(all P>0.05).And between left and right UF,fiber numbers and FA value of control group and fiber numbers of MS group have significant differences(all P<0.05).(3)Negative correlations were found between FA value of cingulum and UF and EDSS scores in MS group(r =-0.572、-0.665,both P<0.05),and that positive correlations were found between MD value and EDSS scores(r=0.627、0.603,both P<0.05).However,there were no significant correlations between the parameters in the fiber pathway and disease duration and MMSE scores in the MS group.Conclusions:(1)The fiber pathways of the hippocampus-thalamus-frontotemporal lobe circuit in the MS patients’ limbic system were affected by MS microscopic pathological attacks,existing extensive demyelinating damage.However,DTI tractography can help to quantify and visualize MS microstructural damage,playing an important role in clinical application.(2)Comparison of bilateral UF in normal controls suggested that UF diffusion parameters were related to the subjects’ handedness.However,in the MS group,the fibers number of right UF was more than left and there was no difference in left and right FA values,indicating that MS pathological damage in UF may be mainly reflected in FA value reduction,and that the damage extent on the left and right sides was not parallel.(3)The correlation between the FA values of cingulum and OF with the EDSS scores in the MS group can partly predict the progression of MS disease.For there were no significant correlations between the parameters of the MS fiber pathways and disease duration and MMSE scores,the more samples and clearer cognitive scale assessment are needed in further study. |
