To compare the integrity of the superior cerebellar peduncle (SCP) and dentato-rubro-thalamic tract (DRTT) across two clinical variants of progressive supranuclear palsy (PSP) that had autopsy confirmation of PSP pathology. 

Diffusion tensor Imaging (DTI) can be used to assess microstructural damage of SCP and DRTT in PSP Richardson’s syndrome (PSP-RS) and PSP with a predominant speech and language disorder (PSP-SL). No studies have assessed these two tracts in clinical variants from an autopsy confirmed PSP cohort. 

Twenty autopsy-confirmed patients with PSP pathology (10 PSP-RS and 10 PSP-SL) had undergone antemortem 3T head MRI. DTI was used for whole-brain tractography reconstructions of brain fiber bundles and to identify the SCP and DRTT. From each tract, fractional anisotropy (FA) and mean diffusivity (MD) were calculated.  Kruskal-Wallis (KW) rank-sum test and hierarchical linear model (HLM), were applied. Diffusivity parameters were correlated to the following clinical scales  PSP Saccadic Impairment Scale (PSIS), PSP rating scales, and Unified Parkinson's Disease Rating Scale part III (MDS-UPDRS III). 

Tractography changes show that phenotypical variability in PSP is likely related to differential impairment in the the SCP and DRTT.