The innervation of the human posterior cricoarytenoid muscle: evidence for at least two neuromuscular compartments.

Recent work has demonstrated that the dog posterior cricoarytenoid (PCA) muscle is composed of three neuromuscular compartments: a vertical, an oblique, and a horizontal. In this study, the human PCA muscle was examined for evidence of neural compartments. Fifteen human PCA muscles were processed by Sihler's stain, which renders the muscle translucent while counterstaining the nerve supply. The results clearly show that in all specimens the nerve supply of the human PCA muscle is separated into at least two main branches: one supplies the horizontal compartment and a second further subdivides to innervate both the vertical and oblique compartments. In 10 of the specimens, these nerve branches arose as separate branches from the recurrent laryngeal nerve. In all specimens, the nerve branch to the horizontal compartment was either combined or connected with the nerve branch to the interarytenoid muscle. The results suggest that the different compartments of the PCA muscle have distinct functions. In addition, the strong connections with the interarytenoid nerve complicate reinnervation procedures to reanimate a paralyzed or transplanted larynx.