Extralaryngeal divisions of the recurrent laryngeal nerve. Surgical and clinical significance.

Extralaryngeal branches of the recurrent laryngeal nerve have been noted in the literature, but frequently the researchers fail to indicate with accuracy the site of bifurcation. The current study was undertaken to designate the exact level of bifurcation of the recurrent laryngeal nerve, with more precise localization using a standard anatomic landmark. A prospective study based on 83 surgical patients was performed. The location of all nerves was measured using the inferior border of the cricoid cartilage as the anatomic landmark. A total of 153 recurrent laryngeal nerves were observed. Sixty-three (41.2 percent) bifurcated or trifurcated into extralaryngeal branches. Of these, there were four instances of trifurcations. The remaining 59 nerves bifurcated. Of these, 14 nerves bifurcated into equal-sized branches which went in an anterior or posterior direction. The remaining 45 nerve bifurcations indicated that 39 (86.7 percent) of the small branches went in a posterior direction, whereas only 6 (13.3 percent) of the large branches went in that direction. Surgical and clinical implications of this finding were discussed. Two instances of a "nonrecurrent" laryngeal nerve (that occurred on the right side) were also noted. The results of this study demonstrate conclusively that extralaryngeal branches of the recurrent laryngeal nerve are not an anatomic rarity. Therefore, thyroid surgery must include identification and preservation of the recurrent laryngeal nerve and all of its divisions.