Author(s)
Neel K Bhatt , MD
Hans Baertsch, Tanya K Meyer, David J Marcinek, Albert L Merati, Jay T Rubinstein, Randal C Paniello, Allen D Hillel
Affiliation(s)
University of Washington; Washington University;
Abstract:
Objective: Age-related vocal atrophy is associated with dysphonia, communication difficulty, and reduced quality of life. Nerve conduction studies (NCS) are the gold-standard measure to diagnose and manage many neuromuscular disorders. With aging, NCS performed in other anatomic locations have been shown to quantify neuromuscular changes. We hypothesize that laryngeal NCS are a feasible technique and can detect electrophysiologic changes in the aging larynx.
Methods: Laryngeal NCS were performed in non-aged (2mo) rats. A bipolar stimulating electrode was placed on the recurrent laryngeal nerve (RLN) 5mm below the cricoid cartilage. Via direct laryngoscopy, the active electrode was placed transorally into the thyroarytenoid muscle. The RLN was maximally stimulated to determine the compound motor action potential (CMAP). Three consecutive trials were averaged. NCS were also performed on the gastrocnemius muscle, which is well-known model in aging research. The rat larynx, RLN, and hindleg tissues were harvested for histology.
Results: Laryngeal NCS were performed in 25 rats. The average RLN stimulating threshold to achieve a CMAP was 1.5±0.6mA in non-aged rats. RLN stimulation caused a visible adductor twitch of the vocal fold in all animals. The mean CMAP amplitude was 1.7±0.5mA and the total area was 1.3±0.3mA2. The onset latency and CMAP duration were 1.0ms±0.1 and 2.4±0.9ms, respectively.
Conclusions: Laryngeal NCS are a feasible investigational tool to quantify laryngeal innervation in a rat model. This measure may identify electrophysiologic changes in the aged larynx. This work could provide a valuable model for studying age-related voice disorders and identifying targets for regenerative treatments.