Usefulness of the superior cerebellar peduncle for differential diagnosis of progressive supranuclear palsy: A meta-analysis.

Previous studies have reported the usefulness of superior cerebellar peduncle (SCP) abnormalities in diagnosing progressive supranuclear palsy. However, the results of these studies were heterogeneous. In the present meta-analysis, we aimed to establish more robust evidence of SCP abnormalities in progressive supranuclear palsy, and to determine the cause of the previously reported heterogeneity. We identified six studies on SCP size and three studies on apparent diffusion coefficient. Key features of each study were extracted and standardized differences in size and apparent diffusion coefficient values were calculated. There was some heterogeneity in terms of the reduction in SCP size in patients with progressive supranuclear palsy compared to those with Parkinson's disease. Moreover, age and Hoehn-Yahr stage negatively correlated with standardized mean difference in SCP size between patients with progressive supranuclear palsy and Parkinson's disease. There was homogenous agreement that the SCP was smaller in patients with progressive supranuclear palsy compared to those with multiple system atrophy. Finally, in terms of apparent diffusion coefficient, there was no significant difference between patients with progressive supranuclear palsy, Parkinson's disease, or multiple system atrophy. Together, these findings suggest that SCP size, when corrected for age and disease severity, could be a diagnostic tool for progressive supranuclear palsy.