Diagnostic potential of dentatorubrothalamic tract analysis in progressive supranuclear palsy.

BACKGROUND:The differentiation of progressive supranuclear palsy-parkinsonism (PSP-P) from Parkinson's disease (PD) remains a major clinical challenge. OBJECTIVES:To evaluate the diagnostic potential of observer-independent assessments of microstructural integrity within infratentorial brain regions to differentiate PSP-Richardson's syndrome (PSP-RS), PSP-P and PD. METHODS:3T MRI parameters of mean diffusivity, fractional anisotropy, grey and white matter volumes from patients with PSP-RS (n = 12), PSP-P (n = 12) and mean disease duration of 2.4 ± 1.7 years were compared with PD patients (n = 20) and healthy controls (n = 23) by using statistical parametric mapping and the spatially unbiased infratentorial template. Subsequently MRI measurements of the dentatorubrothalamic tract were determined observer-independently by a validated probabilistic infratentorial atlas. The impairment of gait and postural stability was evaluated by a sum-score derived from the Unified Parkinson Disease Rating Scale. RESULTS:Significant mean diffusivity increases, fractional anisotropy decreases and corresponding volume loss were localized in mesencephalic tegmentum, superior cerebellar peduncle, decussation of superior cerebellar peduncle and dentate nucleus in PSP-RS and PSP-P compared to PD and healthy controls. Altered microstructural integrity of the dentatorubrothalamic tract in PSP-RS was significantly more pronounced compared to PSP-P and correlated significantly with the gait and postural stability sum-score. Linear discriminant analysis identified diffusion tensor imaging measures of the dentatorubrothalamic tract and the gait and postural stability sum-score to classify correctly 95.5% of PRP-RS, PSP-P and PD patients. CONCLUSIONS:Observer-independent analysis of microstructural integrity within the dentatorubrothalamic tract in combination with assessments of gait and postural stability differentiate PSP-P from PSP-RS and PD in early to moderately advanced stages.