Tongue weakness, jaw adaptation key focus points
Motor neuron diseases, such as amyotrophic lateral sclerosis (ALS), have a devastating effect on speech muscle function that often results in severe communication deficits. A recent study aimed to determine the effect of disease-related changes in tongue–jaw movement coupling on speech intelligibility in persons at different stages of bulbar ALS.
Parallel factor analysis was used to quantify the pattern of spatial coupling between 4 semi-independent regions of the tongue and the jaw in various vowels and consonants in 10 individuals with ALS and 10 healthy individuals. The relation of spatial tongue–jaw coupling to speech intelligibility was examined in individuals at the early and late stages of bulbar ALS and healthy individuals.
Tongue movement, independent of the jaw, decreased early and progressively, which negatively impacted speech intelligibility. Jaw contribution to tongue movement was increased during the early stages of bulbar ALS compared to that of the healthy subjects, which was followed by a decrease during the late stages of bulbar ALS. The early-stage increase of jaw contribution significantly improved speech intelligibility and is thus most likely to be an adaptive strategy to mitigate the negative impact of tongue movement reductions on speech intelligibility.
Continued monitoring of these changes may be critical to guiding clinical management of loss of speech abilities in patients with ALS.