Recurrent laryngeal nerve transection and anastomosis: rat laryngeal motoneuron survival and effect of the anastomosis site.

We investigated the quantity of recurrent laryngeal nerve motoneurons (RLNMs) that survive after transection and anastomosis of the rat recurrent laryngeal nerve (RLN), as well as the impact of the anastomosis site on RLN regeneration. Ten rats underwent right RLN transection and anastomosis. After 16 weeks, Fluoro-Ruby (FR) was applied to the RLN that was transected proximal or distal to the anastomosis site. The brain stems were harvested, and the nucleus ambiguus was evaluated for labeled RLNMs. The RLNM counts were compared to each other and to those from 3 control rats in which FR was applied to an acutely transected RLN. The number of RLNMs that were stained after RLN transection, anastomosis, and regeneration was consistent with the total number of RLNMs in the nucleus ambiguus of control rats. This finding confirms that most RLNMs survived after RLN transection and anastomosis. The quantity of labeled RLNMs was statistically similar whether the FR was applied proximal or distal to the anastomosis, implying that most of the viable axons that were present proximal to the anastomosis crossed into the distal nerve. Rat RLNMs survive nerve transection, anastomosis, and regeneration. The anastomosis site does not significantly impede axonal regeneration, and most of the axons traverse the anastomosis into the distal nerve.