Articulatory Kinematic Characteristics Across the Dysarthria Severity Spectrum in Individuals With Amyotrophic Lateral Sclerosis.

Purpose: The current study investigated whether articulatory kinematic patterns can be extrapolated across the spectrum of dysarthria severity in individuals with amyotrophic lateral sclerosis (ALS). Method: Temporal and spatial articulatory kinematic data were collected using electromagnetic articulography from 14 individuals with dysarthria secondary to ALS and 6 typically aging speakers. Speech intelligibility and speaking rate were used as indices of severity.
Results: Temporal measures (duration, speed of articulators) were significantly correlated with both indices of severity. In speakers with dysarthria, spatial measures were not correlated with severity except in 3 measures: tongue movement displacement was more reduced in the anterior-posterior dimension; jaw movement distance was greater in the inferior-superior dimension; jaw convex hull area was larger in speakers with slower speaking rates. Visual inspection of movement trajectories revealed that overall spatial kinematic characteristics in speakers with severe dysarthria differed qualitatively from those in speakers with mild or moderate dysarthria. Unlike speakers with dysarthria, typically aging speakers displayed variable tongue movement and minimal jaw movement. Conclusions: The current study revealed that spatial articulatory characteristics, unlike temporal characteristics, showed a complicated pattern across the severity spectrum. The findings suggest that articulatory characteristics in speakers with severe dysarthria cannot simply be extrapolated from those in speakers with mild-to-moderate dysarthria secondary to ALS.