Neuropathological correlates of dysarthria in progressive supranuclear palsy.
BACKGROUND: The dysarthria of progressive supranuclear palsy consists of prominent hypokinetic and spastic components with less prominent ataxic components. OBJECTIVE: To correlate the types of dysarthria with neuropathological changes 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 findings. A dysarthria assessment was performed a mean +/- SD of 31 +/- 15 months (range, 10-53 months) before death. The deviant speech dimensions were rated on a scale of 0 (normal) to 3 (severe). The neuropathological examination consisted of semiquantitative analysis of neuronal loss and gliosis by investigators (A.A.F.S., and L.A.B.) blinded to the clinical findings. Correlation and linear regression analysis were used to correlate the severity of the hypokinetic, spastic, and ataxic components with the degree of neuronal loss and gliosis in predetermined anatomical sites. RESULTS: All patients had hypokinetic and spastic dysarthria, and 9 also had ataxic components. The severity of the hypokinetic components was significantly correlated with the degree of neuronal loss and gliosis in the substantia 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 striatum or globus pallidus (/r/<0.34, P>.20). The severity of the spastic and ataxic components was not significantly correlated with the neuropathological 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 may result from degenerative changes in the substantia nigra pars compacta and pars reticulata and not from changes in the striatum or globus pallidus.