Recurrent laryngeal nerve: Significance of the anterior extralaryngeal branch

IntroductionRecognition of extralaryngeal branching of the recurrent laryngeal nerve (RLN) is crucial, because inadvertent operative division may lead to significant postoperative morbidity. The purpose of this study was to examine the incidence of extralaryngeal bifurcation of the RLN and to demonstrate the location of the motor fibers within the branches of the RLN.MethodsProspective study on 99 patients over 1 year with operative data collected on the branching of a total of 137 RLNs. Operative data obtained included the type of operation, incidence of nerve bifurcation, the distance from the inferior border of the cricothyroid to the point of bifurcation, and the location of the motor fibers to the intrinsic muscles of the larynx within the branches of the RLN.ResultsThe RLN was seen intra-operatively in all patients. A total of 137 (right 69, left 68) RLNs in 99 patients undergoing thyroidectomy (total 29; hemi 51), parathyroidectomy (16) and central lymph node dissection (3) were studied. Overall, 46 RLNs (34%) bifurcated prior to entry into the larynx. These bifurcations occurred on the right in 27 (59%) and left 19 (41%). Bilateral bifurcation occurred in 12 (27%) of the 44 patients who underwent bilateral dissections. The median branching distance from the cricothyroid membrane on the right was 8.3 ± 2.5 mm, and on the left was 7.5 ± 1.8 mm. In all bifurcated RLNs, the motor fibers to the vocal cords were located exclusively in the anterior branches.ConclusionExtralaryngeal bifurcation was found in 34% of the RLNs in this case series. The motor fibers of RLN are located in the anterior branch while the posterior branch is only sensory in function. Great caution is, therefore, required after the presumed identification of the RLN to ensure there is no unidentified anterior branch. Identification of the anterior branch may lead to decreased risk of postoperative nerve injury.