Characterizing gait and exploring neuro-morphometry in patients with PSP-Richardson's syndrome and vascular parkinsonism.

Gait differentiation in progressive supranuclear palsy (PSP) and vascular parkinsonism (VaP) is sometimes difficult to detect with the naked eye. Here, we compared specific gait parameters, neuro-morphometric indices, and their associations between patients with PSP Richardson's syndrome (PSP-RS) and VaP. A total of 18 PSP-RS and 13 VaP patients were recruited. Spatio-temporal gait parameters (GAITRite®) and neuroanatomical morphometry (FreeSurfer pipeline) were assessed. The groups were compared using unpaired t-tests involving 10000 random permutations after statistically controlling for total UPDRS-III and H&Y scores. Statistically significant differences between the groups were decided at < 5% Benjamini-Hochberg False Discovery Rate (FDR) for multiple-comparison related corrections. Spearman's correlations were performed to assess the significant associations (p < 0.05) between the gait parameters and morphometry indices. Among all the spatio-temporal gait parameters, PSP-RS patients displayed greater stride time, step time, swing time, and stance time variabilities compared to VaP. Morphometric analyses showed that thalamus, and caudate volumes were significantly lower, but cerebellar cortex, hippocampus, amygdala, accumbens, and putamen volumes were higher in PSP-RS than VaP. Moreover, the bilateral insula was significantly thinner in VaP than in PSP-RS. Correlation analyses support the involvement of limbic structures besides cerebellum in postural control during self-paced walking of PSP-RS patients. Our findings underline the importance of examining individual brain regions to understand the association of cortical and subcortical morphometric estimates and gait variability parameters in PSP-RS and VaP. This study suggests the involvement of the limbic system in addition to the classical neural structures for motor control and gait.