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.
Highlights
In a rapidly ageing society, voice problems will become a major challenge within the near future
When type I and II fibers of the thyroarytenoid muscle (TAM) were analysed as one group, we found a significant shift in mean fiber diameter (MFD) towards larger diameters in the stimulated side: The mean muscle fiber diameter of the stimulated TAM was significantly larger than the non-stimulated TAM (30μm±1.1μm vs. 28μm±1.1 μm, p
As current treatment modalities for presbyphonia are often cost-intensive and unsatisfactory, there is a strong demand for novel approaches which can ameliorate age-related voice impairments
Summary
In a rapidly ageing society, voice problems will become a major challenge within the near future. The population aged 65 years or over will account for 28.7% of the EU-28’s population by 2080, compared with 18.5% in 2014 [1]. The incidence of disordered vocal function in elderly patients in modern Western societies is usually estimated from 12 to 35% [2,3]. Weakening of the voice has long been neglected, but gained consideration lately, as vocal endurance is required in many professions up to higher ages. PLOS ONE | DOI:10.1371/journal.pone.0167367 November 28, 2016
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