We investigated the diagnostic accuracy of brainstem MRI measurements in patients with different progressive supranuclear palsy (PSP) syndromes and Parkinson's disease (PD). Using 3D T1-weighted images, midbrain, and pons areas, as well as superior (SCP) and middle cerebellar peduncle (MCP) widths were measured in 10 patients with Richardson's syndrome (PSP-RS), 10 patients with PSP-parkinsonism (PSP-P), 25 patients with PD, and 24 healthy controls. The ratio between pons and midbrain areas (pons/midbrain), that between MCP and SCP widths (MCP/SCP), and the MR parkinsonism index ([pons/midbrain]*[MCP/SCP]) were calculated. The pons/midbrain and the MR parkinsonism index allowed to differentiate PSP-RS from PD with high sensitivity (90%, 100%), specificity (96%, 92%), and accuracy (94%, 97%). Only the pons/midbrain was found to distinguish PSP-P from PD, but with a lower diagnostic accuracy (sensitivity = 60%, specificity = 96%, accuracy = 86%). Compared to PSP-RS, PSP-P experience a relatively less severe involvement of infratentorial brain. The pons/midbrain looks as a promising measure in the differentiation of individual PSP-P from PD patients.
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