Differential Pattern of Cerebellar Atrophy in Tremor-Predominant and Akinetic/Rigidity-Predominant Parkinson's Disease.

Parkinson's disease (PD) is an akinetic-rigid disorder characterized by basal ganglia dysfunction and a possible cerebello-thalamo-cortical circuit involvement. This study aims to investigate the pattern of cerebellar involvement in PD and to assess whether it correlates with clinical parameters. MRI scans were acquired from 50 healthy controls (HC) and 63 patients; 44 were classified as tremor-predominant-PD (PDT) and 19 as akinetic/rigidity-predominant-PD (PDAR). We designed an analysis of covariance including the three groups and contrasted as follows: (1) all 63 PD vs HC, (2) PDT vs HC, (3) PDAR vs HC, and (4) PDT vs PDAR. For a precise evaluation of the cerebellum, we used the SUIT tool for voxel-based morphometry. Applying p = 0.001 and extent threshold = 20 voxels, the overall PD group vs HC showed decreased gray matter (GM) in the left lobules VI and crus I. The PDT group showed decreased cerebellar GM when compared with HC at left lobules VI, VIIb, and VIIIa; at right lobules Crus I, VIIb, and VIIIb; and vermal lobules VI and VIIIa. When compared with PDAR, PDT also showed a decrease in the left lobules VIIIa (p < 0.001). There were small clusters of both positive and negative correlation between disease duration and PDT group. The PDAR group showed no cerebellar changes. Our findings support the growing evidence of cerebellar involvement in the pathogenesis of the resting tremor.

Pattern of Reduced Functional Connectivity and Structural Abnormalities in Parkinson's Disease: An Exploratory Study.

BACKGROUND: MRI brain changes in Parkinson's disease (PD) are controversial. OBJECTIVES: We aimed to describe structural and functional changes in PD. METHODS: Sixty-six patients with PD (57.94 ± 10.25 years) diagnosed according to the UK Brain Bank criteria were included. We performed a whole brain analysis using voxel-based morphometry (VBM-SPM 8 software), cortical thickness (CT) using CIVET, and resting-state fMRI using the Neuroimaging Analysis Kit software to compare patients and controls. For VBM and CT we classified subjects into three groups according to disease severity: mild PD [Hoehn and Yahr scale (HY) 1-1.5], moderate PD (HY 2-2.5), and severe PD (HY 3-5). RESULTS: We observed gray matter atrophy in the insula and inferior frontal gyrus in the moderate PD and in the insula, frontal gyrus, putamen, cingulated, and paracingulate gyri in the severe groups. In the CT analysis, in mild PD, cortical thinning was restricted to the superior temporal gyrus, gyrus rectus, and olfactory cortex; in the moderate group, the postcentral gyrus, supplementary motor area, and inferior frontal gyrus were also affected; in the severe PD, areas such as the precentral and postentral gyrus, temporal pole, fusiform, and occipital gyrus had reduced cortical thinning. We observed altered connectivity at the default mode, visual, sensorimotor, and cerebellar networks. CONCLUSION: Subjects with mild symptoms already have cortical involvement; however, further cerebral involvement seems to follow Braak's proposed mechanism. Similar regions are affected both structurally and functionally. We believe the combination of different MRI techniques may be useful in evaluating progressive brain involvement and they may eventually be used as surrogate markers of disease progression.