Progressive Gray Matter Atrophy In Multiple System Atrophy Assessed With MR Imaging By Using Causal Structural Covariance Network

BackgroundMultiple system atrophy(MSA)is a rare neurodegenerative disease,and it is usually accompanied by brain structural alterations as the disease progresses.As the neuroimaging technology develops,structural magnetic resonance imaging(MRI)technology has been widely used in the researches of the brain structural changes.At present,Voxel-based morphometry(VBM)analysis,a handy tool,is generally used to explore gray matter alterations in MSA.ObjectiveIn this study,we use VBM to measure progressive gray matter alterations in MSAparkinsonian type(MSA-P)and investigate the temporal and causal relationships of structural changes by causal network analysis.MethodsT1-weighted MRI of thirty-five MSA-P patients and thirty-five healthy controls were recruited.VBM method was adopted to measure gray matter volume(GMV)for each participant.All patients were divided into three subgroups according to illness duration,then we assessed stage-specific GMV alterations and the causal relationships of structural changes as the illness duration prolonged using the causal network analysis of structural covariance.ResultsWith greater illness duration,the gray matter volume reduction was originated from the right cerebellum and progressed to the bilateral cerebellum,fusiform gyrus,insula,putamen,caudate nucleus,the frontal lobe,right angular gyrus,right precuneus,left middle occipital lobe and left inferior temporal lobe,and then expanded to the midbrain,bilateral para-hippocampus,thalamus,temporal lobe,inferior parietal lobule,precentral gyrus,postcentral gyrus and middle cingulate cortex.The right cerebellum was revealed to be the core node of the directional network,and the positive causal effects projected from right cerebellum to the bilateral cerebellum,caudate nucleus and the left inferior parietal lobule.ConclusionMSA-P patients show progression of gray matter abnormalities over time,with the right cerebellum as the primary hub.And the early structural vulnerability of cerebellum in MSA-P may play a pivotal role in the modulation of motor and non-motor circuits at the structural level.