Reversing age related changes of the laryngeal muscles by chronic electrostimulation of the recurrent laryngeal nerve

Abstract

Age related atrophy of the laryngeal muscles -mainly the thyroarytenoid muscle (TAM)-leads to a glottal gap and consequently to a hoarse and dysphonic voice that significantly affects quality of life. The aim of our study was to reverse this atrophy by inducing muscular hypertrophy by unilateral functional electrical stimulation (FES) of the recurrent laryngeal nerve (RLN) in a large animal model using aged sheep (n = 5). Suitable stimulation parameters were determined by fatiguing experiments of the thyroarytenoid muscle in an acute trial. For the chronic trial an electrode was placed around the right RLN and stimulation was delivered once daily for 29 days. We chose a very conservative stimulation pattern, total stimulation time was two minutes per day, or 0.14% of total time. Overall, the mean muscle fiber diameter of the stimulated right TAM was significantly larger than the non-stimulated left TAM (30μm±1.1μm vs. 28μm±1.1 μm, p<0.001). There was no significant shift in fiber type distribution as judged by immunohistochemistry. The changes of fiber diameter could not be observed in the posterior cricoarytenoid muscle (PCAM). FES is a possible new treatment option for reversing the effects of age related laryngeal muscle atrophy.