Sexual Dimorphism in the Human Vocal Fold Innervation

This study investigated the sexual dimorphism in the recurrent laryngeal nerve (RLN) and thyroarytenoid (TA) muscle, which control the vocal fold. The RLN and TA were bilaterally studied in human specimens obtained from necropsies (seven men and seven women). Analysis of the morphometric parameters showed that the RLN of the men were significantly larger, as shown by the intraperineural area (42.5%) (P = 0.006), total number of fibers (38.0%) (P = 0.0002), axonal area (34.3%) (P = 0.0001), axonal diameter (19.0%) (P = 0.0001), and the area of the nerve occupied by myelinated fibers (34.9%) (P = 0.001). By contrast, in women, our results showed that the area of the RLN occupied by endoneurial connective tissue was larger (5.7%) (P = 0.001). Estimation of the fiber area and shape coefficient showed that the histologic organization of TA is similar in men and women. These results may contribute toward enhancing our understanding about the voice neurobiology.