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

ABSTRACT

PURPOSE: 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. METHODS: 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). RESULTS: 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. CONCLUSION: 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.