Voxelwise meta-analysis of gray matter anomalies in Parkinson variant of multiple system atrophy and Parkinson's disease using anatomic likelihood estimation.

Numerous voxel-based morphometry (VBM) studies on gray matter (GM) in patients with the Parkinson variant of multiple system atrophy (MSA-P) and Parkinson's disease (PD) have been separately conducted. Identifying the different neuroanatomical changes in GM between MSA-P and PD through meta-analysis may aid the differential diagnosis of MSA-P and PD. A systematic review of VBM studies on patients with MSA-P and PD compared to healthy controls (HC) from the PubMed and Embase databases between January 1995 and June 2014 was conducted. Five studies comparing MSA-P with HC and twenty-three studies comparing PD with HC were included. The anatomical distribution of the coordinates of GM volume (GMV) differences was analyzed using the anatomical likelihood estimation (ALE) method. GMV reductions were present in the bilateral putamen, claustrum, insula, midbrain and left cerebellum in MSA-P. In PD, GMV decreases were present in the frontal, parietal, occipital and limbic lobes. Subtraction meta-analysis was performed to explore the differences in GM abnormalities between MSA-P and PD during the early stage of the disease. For patients with disease duration within 5 years, compared with PD, the decrease in GMV focused on the bilateral putamen and claustrum in MSA-P. In contrast, for patients with disease duration within 3 years, no significant GMV difference was found between MSA-P and PD. Our meta-analysis indicated that the atrophy of bilateral putamen or claustrum is not a neuroanatomical marker for distinguishing MSA-P from PD during the early stage by using the VBM method.