Tongue strength in progressive supranuclear palsy

Purpose: Tongue weakness is common in patients with neurologic disease, including parkinsonism. The aim of this study is to describe tongue strength in progressive supranuclear palsy and its relationship to dysphagia and dysarthria. Methods: Participants were 119 (58 female) individuals with probable or possible progressive supranuclear palsy. Each participant underwent a motor speech assessment to determine type and severity of dysarthria. Quantification of dysphagia included the Modified Barium Swallow Impairment Profile, the Penetration-Aspiration Scale, and the Functional Oral Intake Scale. Anterior elevation tongue strength was assessed by measuring maximum pressure exerted by the tongue on an air-filled bulb positioned against the hard palate. Results: Mean maximum tongue elevation pressure was 38 kPa. Tongue strength correlated significantly with age, dysarthria severity, and disease severity. Tongue strength was not differentially affected by dysarthria type, but was weakly correlated with pharyngeal dysphagia severity. Conclusions: Average tongue strength in speakers with progressive supranuclear palsy is lower than reported for neurologically healthy adults and for patients with Parkinson's Disease. Likely reflecting a combination of age-related loss of muscle mass and damage to the basal ganglia and/or pyramidal tracts, reduced tongue strength on its own does not appear to be a primary driver of swallowing difficulties in this population. Further study is warranted to better understand the physiologic mechanisms contributing to reduced tongue strength in PSP, how tongue strength changes as disease progresses, and what other mechanisms contribute to dysphagia in PSP.