Stylohyoid and Posterior Digastric Recruitment Pattern Evaluation in Swallowing and Non-swallowing Tasks

Objectives

Electromyography is one of the few measurement methods that can be implanted, and it has been used in swallowing detection to measure superficial muscles, but has failed to provide satisfactory performances for a real-time detection. Yet, we seek to allow for the feasibility of an implantable active artificial larynx that would protect the airway during swallowing. Therefore, it requires a real-time detection of swallowing through measurements that must provide dedicated and early activity on swallowing, to close the airways soon as possible. In that regard, promising results were published about the stylohyoid and posterior digastric muscles, but no study provided simultaneous and independent measurements. So, this paper aims to evaluate both muscles with intra muscular EMG, in a large set of tasks, to evaluate their recruitment pattern for the feasibility of an implantable active artificial larynx.

Materials and methods

we used intramuscular EMG to measure the stylohyoid and the posterior digastric muscles independently. We also used surface electrodes to measure the submental muscles and provide a basis for comparison. Besides, the swallowing sound measurement method was used to locate the moment the bolus starts to enter the upper esophageal sphincter (UES). That moment defines a temporal limit after which the airway are in danger of aspiration and the temporal evolution of the muscles' is evaluated in comparison to that limit. The onsets and offsets of each muscles were located with a generalized likelihood ratio method, and the UES bolus passage was localized manually after the transformation of the signals with a Teager-Kaiser energy operator. 17 participants were measured, and were asked to perform 4 swallowing tasks and 13 non-swallowing tasks.

Results

we found a strong implication of the stylohyoid for swallowing and mastication. The posterior digastric showed a clear tendency towards swallow-related tasks, and especially swallowing, mastication, open mouth, jaw, and clench teeth. Both muscles provided significant activity before the temporal limit, with a characteristic pattern.

Conclusion

the stylohyoid and the posterior digastric muscles shows a net increase in potential for a detection, compared to the submental muscles, for the feasibility of an implantable active artificial larynx.