Atrophy of superior cerebellar peduncle in progressive supranuclear palsy

Background: Pathologic changes in the superior cerebellar peduncles (SCP) are common in progressive supranuclear palsy (PSP), but atrophy of the SCP has never been systematically studied. Objective: To investigate the SCP width in PSP cases and controls with morphometric methods. Methods: The mean width of the SCP in transverse sections of the pons at the level of trigeminal nerve was determined in 48 PSP cases (29 men, 19 women; mean age 72.5 ± 8.2 years) and 29 age-matched control subjects, many with neurodegenerative disorders that can be clinically mistaken for PSP. As the origin of the SCP is the cerebellar dentate nucleus, correlations were sought between SCP atrophy and severity of grumose degeneration in the dentate nucleus. Results: The average width of the SCP was less in PSP (range 0.09 to 0.24 cm) than in controls (range 0.21 to 0.43 cm; Mann-Whitney U test, p < 0.001), including control cases that had been clinically misdiagnosed as PSP (range 0.26 to 0.41 cm). Severity of SCP atrophy normalized by brain weight correlated with disease duration (Spearman rank order correlation, r = 0.367, p = 0.028), suggesting that SCP atrophy is a relatively early feature of PSP. No correlation was found between grumose degeneration and SCP width. Conclusions: SCP atrophy is common in PSP and correlates with disease duration. Given that measurements of the SCP are within the resolution of MRI, it remains to be determined if SCP atrophy can be used as a diagnostic marker of PSP.