Imaging counterpart of postural instability and vertical ocular dysfunction in patients with PSP: A multimodal MRI study

We investigated the imaging counterpart of two functional domains (ocular motor dysfunction and postural instability) in progressive supranuclear palsy (PSP) patients classi ed according to the new clinical diagnostic criteria. Methods: Forty-eight patients with probable PSP-Richardson's syndrome (PSP-RS), 30 with probable PSP-par- kinsonism (PSP-P), 37 with Parkinson's disease (PD), and 38 controls were enrolled. For each functional domain, PSP patients were strati ed by two certainty levels: vertical supranuclear gaze palsy (O1) and slowness of vertical saccades (O2) for ocular motor dysfunction; early unprovoked falls and tendency to fall on the pull-test for postural instability. Voxel-based morphometry (VBM), whole-brain fractional anisotropy (FA) and MR pla- nimetric measurements were analysed and compared across patient groups. Results: O1 was present in 64%, and O2 in 36% of all PSP patients. All PSP-RS patients showed early unprovoked falls. TBSS whole-brain analysis revealed that superior cerebellar peduncles (SCPs) were the only structures with signi cantly lower FA values in PSP-RS compared with PSP-P patients. PSP/O1 patients had lower FA values in midbrain than PSP/O2 patients. By contrast, VBM revealed no di erences in grey matter volume between PSP patient groups. MR Planimetric measurements con rmed atrophy of midbrain and SCPs, in line with DTI ndings. Conclusions: Our study demonstrates that SCPs were signi cantly more damaged in patients with PSP-RS in comparison with PSP-P patients, thus suggesting the role of SCPs in developing postural instability. Midbrain damage was less severe in O2 than in O1 patients, suggesting that the degree of vertical ocular dysfunction re ects the severity of midbrain atrophy.