Surgical anatomy of the ansa cervicalis nerve: which branch to use for laryngeal reinnervation in humans?

Abstract

The aim of this study has been to obtain some data for the selection of which branch of the ansa cervicalis nerve (AC) could be an attractive candidate for a laryngeal reinnervation using AC to recurrent laryngeal nerve (RLN) neurorrhaphy. The AC was dissected in ten human head cadavers with an operating microscope. A vagal nerve stimulation was conducted during a bilateral thyroidectomy with normal vocal fold mobility in ten patients using a NIM Medtronic System(®) to record phasic activity within the thyroarytenoid muscle (vocal fold adduction) and one of the infrahyoid muscle (sternothyroid muscle or sternohyoid muscle). Despite reported variations of the roots of AC and location of its loop, the lower portion of the STM and SHM was innervated by a prominent common trunk in 80 % of cases, in a close vicinity of the RLN with an excellent size match to the RLN for a tension-free anastomosis. The STM displays slight but significant electrical activity during vocal fold adduction. The common trunk of the SHM and STM is the prime choice for laryngeal reinnervation using AC-RLN non-selective anastomosis. If the main trunk is missing, the branch to the STM can be an attractive candidate.