Alterations of brain activity in different motor subtypes of Parkinson disease based on regional homogeneity analysis

Objective To explore the changes and significance of local brain activity in different motor subtypes of Parkinson disease(PD) using resting-state functional MRI (rs-fMRI) based on regional homogeneity (ReHo) analysis. Methods A total of 84 PD patients and age-and gender-matched 29 healthy controls undergoing rs-fMRI were included. PD patients were divided into two groups of tremor dominant(TD) (n=45) and postural instability gait difficulty(PIGD) (n=39) according to the Unified Parkinson′s Disease Rating Scale (UPDRS) scores. Data processing assistant for resting-state fMRI (DPARSF) and resting-state fMRI data analysis Toolkit (REST) V1.8 based on MATLAB were used to calculate the ReHo which measured brain activity in different motor subtypes of PD. Analysis of covariance and post-hoc t-tests were performed to detect the differences of local brain activity among the three groups.Correlation analyses were performed between ReHo values of the regions showing group differences and TD and PIGD scores respectively. Results Compared to healthy controls, the TD group exhibited increased ReHo in the right superior and middle frontal gyrus, left cerebellum(13 to 21 voxels, P<0.05), while decreased ReHo in the left temporal lobule, left putamen, left paracentral lobule, and bilateral thalamus (12 to 91 voxels, P<0.05). The PIGD group showed increased ReHo in the right superior frontal gyrus, right middle frontal gyrus and anterior cingulate gyrus (ACC) (55 to 92 voxels, P<0.05), while decreased ReHo in the left putamen, left pallidum, left temporal lobule, right occipital lobule, bilateral thalamus, bilateral middle cingulate gyrus, bilateral supplementary motor area (SMA) (15 to 78 voxels, P<0.05). Compared with PIGD, the TD group showed increased ReHo in the left temporal lobule, left cerebellum, bilateral middle cingulate gyrus (19 to 51 voxels, P<0.05), whereas decreased ReHo in the left paracentral lobule, bilateral cuneus, right superior frontal gyrus, and right ACC (14 to 68 voxels, P<0.05). Additionally, ReHo in the left thalamus and left putamen negatively correlated with TD scores (r=-0.355 and -0.498, both P<0.05). ReHo in the left thalamus and right thalamus negatively correlated with PIGD scores (r=-0.478 and -0.397, both P<0.05). Conclusions The changes of brain activity in TD are located in the cerebello-thalamo-cortical (CTC) circuit and the striatal-thalamo-cortical (STC) loop while the changes in PIGD are largely located in the STC loop and visual network cortex. This specific pattern of intrinsic activity in TD and PIGD may provide insights into the neurophysiological mechanisms of PD with different motor subtypes. Key words: Parkinson disease; Resting tremor; Postural instability gait difficulty; Magnetic resonance imaging; Regional homogeneity