Disease-Specific Speech Movement Characteristics of the Tongue and Jaw.

Purpose: To advance our understanding of disease-specific articulatory impairment patterns in speakers with dysarthria, this study investigated the articulatory performance of the tongue and jaw in speakers with differing neurological diseases (Parkinson's disease [PD], amyotrophic lateral sclerosis, multiple sclerosis, and Huntington's disease).

Method: Fifty-seven speakers with dysarthria and 30 controls produced the sentence "Buy Kaia a kite" five times. A three-dimensional electromagnetic articulography was used to record the articulatory movements of the posterior tongue and jaw. Sentence-length kinematic measures (e.g., duration, tongue range of motion [ROM], jaw ROM, tongue speed, jaw speed) were extracted.

Results: Results revealed significant group effects for the duration, jaw ROM, and tongue speed but not for tongue ROM. Post hoc pairwise comparisons revealed more significant between-groups differences for duration and jaw ROM than for tongue speed. Statistically significant findings between clinical groups were predominantly driven by the difference between speakers with PD and speakers of other clinical groups.

Conclusions: Reduced jaw ROM and trends toward reduced tongue ROM confirm hypokinesia as a distinguishing motor feature of speakers with PD. However, deviancies in speed or movement duration did not emerge as a distinguishing motor feature for any of the four studied clinical groups. Nevertheless, movement duration, but not movement speed, may be useful to index dysarthria severity.