Submental muscle tissue compliance during relaxation, contraction, and after tone-modification interventions

Deviations in muscle tone are presumed to accompany speech motor control deficits in select forms of dysarthria, although there is little confirmation of these associations. For patients experiencing neuromuscular impairments, therapeutic interventions and/or principles have been devised to alleviate tone deviations where they occur and to prevent the development or exacerbation of tone deviations. Potentially therapeutic effects of these interventions on muscle tone in the speech musculature have not been studied empirically. One reason for the paucity of research is that tools for assessing muscle tone in the speech musculature are not generally available. This pilot study explored the feasibility of a commercially available, handheld instrument for measuring submental muscle compliance during relaxed and active conditions in 16 women with normal speech and swallowing. Additionally, the study examined changes in muscle compliance when interventions presumed to impact muscle tone were applied to the submental region. The Myotonometer was sensitive to changes in tissue compliance related to active contraction of the submental musculature. Applying ice or vibration to the submental region resulted in no systematic changes in submental tissue compliance in the relaxed or contracted state. Additional research is needed to validate the use of this instrument to reliably assess muscle tone and other contributors to tissue compliance. If successful, studies should examine the sensitivity of the Myotonometer to assess intervention-induced tissue compliance changes in patient groups with suspected muscle tone impairments. Further study of intervention effects across muscle groups and dosage levels can help inform clinical decisions about the potential usefulness of tone-altering interventions for the orofacial musculature.