Clinical correlates of white matter tract degeneration in progressive supranuclear palsy.

OBJECTIVES To use diffusion tensor imaging to assess white matter tract degeneration in progressive supranuclear palsy (PSP) and to investigate correlates between tract integrity and clinical measures. DESIGN Case-control study. SETTING Tertiary care medical center. PATIENTS/PARTICIPANTS Twenty patients with probable PSP and 20 age- and sex-matched healthy controls were enrolled. All patients with PSP underwent standardized clinical testing, including the Frontal Behavioral Inventory and Frontal Assessment Battery to assess behavioral change, the PSP Rating Scale to measure disease severity, the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (parts II and III) to measure motor function, and the PSP Saccadic Impairment Scale to measure eye movement abnormalities. METHODS Fractional anisotropy and mean diffusivity were measured using region of interest analysis and tract-based spatial statistics. RESULTS Compared with controls, abnormal diffusivity was observed predominantly in the superior cerebellar peduncles, body of the corpus callosum, inferior longitudinal fasciculus, and superior longitudinal fasciculus in patients with PSP. Fractional anisotropy values in the superior cerebellar peduncles correlated with disease severity (r = -0.59, P = .006), inferior longitudinal fasciculus correlated with motor function (r = -0.51, P = .02), and superior longitudinal fasciculus correlated with severity of saccadic impairments (r = -0.45, P = .047). CONCLUSIONS The results of this study demonstrate that PSP is associated with degeneration of the brainstem, association, and commissural fibers and that this degeneration likely plays an important role in clinical dysfunction.