Myofiber morphology of posterior cricoarytenoid muscles in patients with long-term denervation of recurrent laryngeal nerve / 第二军医大学学报

ABSTRACT

Objective: To study the morphological changes of posterior cricoarytenoid muscles (PCM) in patients with longterm denervation of recurrent laryngeal nerve (RLN), so as to provide theoretical evidence for repair of recurrent laryngeal nerve at advanced clinical stage. Methods: Thirty-eight patients with damaged RLN were divided into 4 groups according to the duration of their RLN damage 6-12 months group (n = 12), 1-2 years group (n = 10), 2-3 years group (n = 8), and over 3 years group (n = 8). Twelve subjects with normal PCM served as control. Trichrome Masson staining and imaging analyzing system were used to quantitatively analyze the transverse section areas of myofibers, collagen fiber and connective tissues. SDH and AchE staining and cell counting method were used to analyze changes of two kinds of myofibers and motor end plate numbers at different times after denervation of recurrent laryngeal nerve. Results: The transverse areas of myofibers gradually decreased and those of collagen fibers gradually increased with the prolongation of denervation; the difference was significant between different groups (P<0.01). The ratio of transverse area of myofiber to that of collagen fibers reached the lowest level 0.5-2 years after denervation. The fibrosis of muscle obviously slowed down 2 years after denervation. The transverse section of 48% of myofibers remained 3 years after denervation, Long-term denervation resulted in the changes of muscle fiber types the ratio of red muscles was increased and the ratio of white muscles was decreased after denervation; the difference was significant between different groups (P < 0.01). The number of motor end plate decreased with the prolongation of denervation and disappeared after 1 year. Conclusion: The morphological alteration in long-term denervation PCM indicates the worst myofibrosis occurs within 2 years of denervation, but 48%of myofibers remain 3 years after denervation. The type alteration of denervated muscles may decrease the apoptosis of skeletal muscle. The structure of myoceptors disappears within 1 year of denervation. Our experiment indicates that there is a morphological basis for regaining total or partial muscle function by nerve repair after long-term denervation.