A first investigation of tongue, lip, and jaw movements in persons with dysarthria due to multiple sclerosis

Abstract

Multiple sclerosis can affect the speech motor system and result in dysarthria. This pilot study sought to identify tongue, lip, and jaw motor deficits in persons with dysarthria due to multiple sclerosis (PwDMS) to better understand the speech motor mechanisms that underlie their aberrant speech. Tongue and jaw movements during / ai / and lower lip and jaw movements during / bob / were examined in eleven PwDMS and fourteen age- and sex-matched controls using threedimensional electromagnetic articulography. Movement duration, maximum displacement, peak speed, stiffness (i.e., peak speed/displacement ratio), and jaw contribution to lower lip and tongue displacements were of particular interest. Whereas most kinematic measures yielded significant between-group differences for tongue and jaw motor performance during / ai /, lower lip and jaw motor performance during /bob/ were mostly comparable between groups. Findings suggest that speech movements of the tongue are differentially more impaired than those of the lower lip in PwDMS. Particularly the ability to move the tongue with adequate speed during speech was significantly impaired in PwDMS, which may explain, in part, their slowed speech rate. Aberrant jaw kinematics during /ai/ may be a compensatory strategy to maximize speech clarity in the presence of the impaired tongue motor performance.