Neuropathological correlates of dysarthria in progressive supranuclear palsy

Background: The dysarthria of progressive supranuclear palsy consists of pr ominent hypokinetic and spastic components with less prominent ataxic compo nents. Objective: To correlate the types of dysarthria with neuropathological chan ges in patients with progressive supranuclear palsy. Design and Methods: In 14 patients with progressive supranuclear palsy, we correlated the perceptual speech findings with the neuropathological findin gs. A dysarthria assessment was performed a mean +/- SD of 31 +/- 15 months (range, 10-53 months) before death. The deviant speech dimensions were rat ed on a scale of 0 (normal) to 3 (severe). The neuropathological examinatio n consisted of semiquantitative analysis of neuronal loss and gliosis by in vestigators (A.A.F.S., and L.A.B.) blinded to the clinical findings. Correl ation and linear regression analysis were used to correlate the severity of the hypokinetic, spastic, and ataxic components with the degree of neurona l loss and gliosis in predetermined anatomical sites. Results: All patients had hypokinetic and spastic dysarthria, and 9 also ha d ataxic components. The severity of the hypokinetic components was signifi cantly correlated with the degree of neuronal loss and gliosis in the subst antia nigra pars compacta (r = 0.61, P = .02) and pars reticulata (r = 0.64 , P = .01) but not in the subthalamic nucleus (r = 0.51, P = .07) or the st riatum or globus pallidus (/r/ < 0.34, P > .20). The severity of the spasti c and ataxic components was not significantly correlated with the neuropath ological changes in the frontal cortex (r = 0.20, P = .50) and cerebellum ( /r/ < 0.28, P > .33), respectively. Conclusion: The hypokinetic dysarthria of progressive supranuclear palsy ma y result from degenerative changes in the substantia nigra pars compacta an d pars reticulata and not from changes in the striatum or globus pallidus.