Topographic anatomy of the external branch of the superior laryngeal nerve. Its importance in head and neck surgery.

The authors have studied the anatomy of the external branch of the superior laryngeal nerve in its entirety on 40 fresh cadavers, and they have drawn the following conclusions: the nerve ramifies from the vagus immediately below the nodose ganglion or in the ganglion itself. The nerve splits into two branches approximately 1.5 cm below the ganglion nodosum. In four cases, both branches originated from the vagus itself. In one case, anastomosis of the external branch of the superior laryngeal nerve with the recurrent nerve was found. The external branch of the superior laryngeal nerve is not usually severed at supraglottic laryngectomy but the nerve is at risk during neck dissections, resection of Zenker's diverticula and thyroidectomy. An accurate knowledge of its course should reduce the incidence of injury to the branches of the superior laryngeal nerve during surgery.