MRI Assessment Of Brain Structural And Functional Changes In Parkinson’s Disease Patients With Hyposmia

Background and purposeParkinson’s disease(PD)is a common neurodegenerative disorder of unknown cause that occurs in older adults.The mean age of onset is about 60 years old.The primary symptoms of PD includes resting tremor,muscular rigidity,bradykinesia and postural instability.Besides motor symptoms,in recent years also noted,almost all PD patients will appear different types and degrees of non-motor symptoms.The life quality of PD patients will be influenced seriously.The non-motor symptoms includes dysosmia,dyssomnia,constipation and so on.Clinically,PD patients ofter experience motor,cognition,and sensory dysfunction,which affects the quality of PD patients’ life seriously.Dysosmia is one of the most common non-motor symptoms in PD patients.The study of dysosmia in PD is helpful to the early diagnosis,antidiastole and pathogenesis of the disease.In recent years,researchers have found that PD with hyposmia has brain structural and functional changes.We aimed to used high resolution MRI,voxel-based morphometry(VBM)analysis and functional connectivity(FC)to research olfactory bulb volume,cortical structural and brain functional changes in Parkinson’s disease patients with hyposmia.Materials and methodsA total of 56 Parkinson’s disease patients with hyposmia and 43 age and gender matched healthy subjects were examined to undergo olfactory test and multimodal MRI techniques.The imaging data were obtained by using Prisma 3.0 Tesla MR scanner.All patients and control persons underwent T2-spc-cor,T1-mprage and resting-state functional magnetic resonance sequences.1.The outline of the olfactory bulb was drawed on the high-resolution coronal images.The olfactory bulb areas multiplied by the thickness made the olfactory bulb volume.The volumes are measured for 3 times,then averaged the results.2.The GMV were calculated by using the VBM technique.This technique was implemented with SPM8 in Matlab.Processing steps included segmented,registration,spatial normalization,resampled and smoothed.3.The rs-fMRI datas were preprocessed by using DPARSFA and SPM8 software.The Processing steps included slice timing,realignment,spatial normalization,filter,resampling and smoothed.Then ROI-based rsFC analysis was performed to analyze that whether there had abnormal functional connection in VBM significant difference regions.4.Two independent samples t test were used between patients and controls in the olfactory bulb volume.The relationship of olfactory bulb volume and the clinical scale scores used spearman correlation analysis with SPSS 19.0.Differences of the GMV and rsFC between PD patients and healthy controls were analyzed by SPM software with the significance level of α = 0.05.Results1.There was statistically significant difference(P < 0.05 was considered as significant)in the left,right and mean olfactory bulb volume between patients and controls(t=-3.804,-4.945,-4.593,P< 0.05).No clear correlation was seen between disease course,H-Y grades,UPDRS scores and olfactory bulb volumes(P< 0.05).Olfactory bulb volumes(P< 0.05)were significant positive correlation with the olfactory score.2.Compared with healthy controls,the PD patients exhibited decreased GMV in bilateral superior temporal gyrus(STG)(P< 0.05,cluster size >1004 voxels).3.Results showed patients exhibited decreased FC in right middle precentral gyrus(MPG)and middle occipital gyrus(MOG)(P < 0.05,cluster size > 139 voxels).Conclusions1.The volume of olfactory bulb in PD patients with dysosmia was significantly reduced,and the quantitative analysis of the olfactory bulb volume was helpful to the assessment of olfactory dysfunction in PD patients.It is very helpful for the clinical diagnoses andtreatment.2.Compared with the normal control group,PD patients with dysosmia had brain structural and functional changes.The main manifestations were volume atrophy and decreased functional connectivity in brain.