Functional Electrical Stimulation (FES)—Therapeutical potentials for presbyphonia

Abstract

Presbyphonia, an age-related decrease in voice quality is a consequence of vocal muscle atrophy. Functional Electrical Stimulation (FES) was introduced as a potential treatment to increase the muscle volume. In this study, we analyzed the effects of FES using ex vivo sheep larynx models. To stimulate the thyroarytenoid muscle, electrodes were implanted at the recurrent laryngeal nerve of 12 sheep (10 y). Stimulation was applied to six sheep for 9 weeks. Afterwards, the excised larynges were fixated in a mechanical setup and analyzed. For different elongations of the VFs, the acoustic signal, the subglottal pressure, and the VF motion were recorded simultaneously. The postprocessing was performed with the Glottis Analysis Tools (GAT) software and SPSS. The results show that the vibration characteristics and sound quality improved for the stimulated larynges. The vibration showed a higher degree of glottis closure (GGI) and symmetry (PAI and ASI), as well as a faster glottis closure (MADR) achieved by FES. Consequently, the sound signal exhibited a larger number of tonal sound components (CPP). Furthermore, a higher correlation between acoustic and subglottal pressure was found indicating an enhanced coupling between sub- and supraglottal regions. The results suggest that FES could be a possible therapy for presbyphonia.