Anatomic considerations of superior laryngeal nerve during anterior cervical spine procedures

Cadavers were dissected anatomically to identify the course of the superior laryngeal nerve relative to the spinal column.

To illustrate the anatomic relation of the SLN with respect to its vulnerability during anterior cervical spine procedures.

There is ample literature referencing the superior laryngeal nerve with respect to head and neck surgery. Detailed descriptions of the anatomy of the recurrent laryngeal nerve are quite extensive in both the spine and head and neck literature. To the authors' best knowledge, no similar reports have delineated the anatomic relation of the superior laryngeal nerve in procedures on the anterior aspect of the cervical spine.

Ten dissections were carried out on human cadavers to show the course of the superior laryngeal nerve. Particular attention was directed to the internal branch of the superior laryngeal nerve to show the overall anatomic relation relative to standard landmarks. These landmarks included the superior laryngeal and superior thyroid arteries, the split of the superior laryngeal nerve, and the intervertebral disc space.

The superior laryngeal nerve originates from the vagus nerve in the carotid sheath and bifurcates into internal and external branches. Distally, the internal branch of the superior laryngeal nerve courses in close proximity with the superior laryngeal artery and inserts within 1 cm superior to the superior laryngeal artery into the thyrohyoid membrane. With respect to the cervical spine, the distal of portion of the internal branch of the superior laryngeal nerve is located between the C3 and C4 vertebral bodies.

The internal branch of the superior laryngeal nerve supplies innervation to the mucosa of the larynx and has an important sensory reflex that serves to protect the lungs from aspiration. Injury to this nerve can predispose the patient to life-threatening pneumonia. It is therefore imperative for the surgeon to recognize the location and course of this nerve to avoid injuring it. Injury most commonly occurs either by excessive retraction in different planes or by accidental ligation of the nerve.