Sympathetic fiber origin of the superior laryngeal nerve and its branches: an anatomic study

An anatomic study of 50 fresh adult human cadavers was carried out to classify the nervous anastomoses between the ipsilateral cervical sympathetic chain (CSC)/superior cervical sympathetic ganglion (SCSG) and the superior laryngeal nerve with its branches (SLNwb). Following the pattern of a prospective randomized study, the necks were dissected bilaterally to identify the SLNwb, CSC and SCSG. The nervous connections between the CSC/SCSG and the SLNwb were grouped according to Sun and Chang's (1991, Surg. Radiol. Anat. 13:175-180) types as well as according to a new classification, tie, based on the location and number of connections between the CSC/SCSG and the SLNwb. Connections between the CSC/SCSG and the SLNwb were found in 95 of 100 dissections. According to our tie classification, the results demonstrated that the e(n) was the most frequent tie group in the sample (59%), followed by t(n) (15%), i(n)e(n) (11%), t(n)e(n) (8%), no nervous anastomosis (5%), and i(n) (2%), where t, i, e represent nervous connections between the CSC/SCSG and the trunk, external branch, and internal branch of the SLN, respectively, and n represents the number of connections. Therefore, the nervous communications between the CSC/SCSG and the SLNwb were frequent and could easily be classified by the origin and number of nervous connections. Although their physiologic role remains unclear, the SLNwb may be an important pathway for nerve fibers from the CSC/SCSG to reach the larynx.