Ultrasound-guided superior laryngeal nerve block is useful in the diagnosis and treatment of painful conditions subserved by the superior laryngeal nerve, including posttrauma pain in the region of hyoid bone and thyroid gland, superior laryngeal neuralgia, hyoid syndrome, as well as painful conditions of the larynx and pharynx above the glottis and pain of malignant origin (Fig. 23.1). This technique is also used as an adjunct to awake endotracheal intubation, extubation, and laryngobronchoscopy.

The superior laryngeal nerve arises from the vagus nerve with a small contribution from the superior cervical ganglion. The nerve passes inferiorly and anteriorly behind the carotid arteries along the side of the pharynx to pass the lateral extent of the hyoid bone where it is accessible for nerve block (Figs. 23.2 and 23.3). Along with the superior laryngeal artery, which is a branch of the superior thyroid artery, the internal branch of the superior laryngeal nerve enters the larynx and pharynx through a foramen in the posteroinferior portion of the thyrohyoid membrane (see Fig. 23.2). It is at this penetration that malignancies tend to spread from the supraglottic region into the larynx (Fig. 23.4). The internal branch of the superior laryngeal nerve provides sensory innervation to the base of the tongue, both surfaces of epiglottis, the aryepiglottic folds, and the vestibule of the larynx to the level of the vocal folds. There are also secretomotor fibers that travel within the internal branch of the superior laryngeal nerve. An external branch provides motor innervation to the internal constrictor and cricothyroid muscles. The superior laryngeal nerve and its branches are susceptible to damage during thyroid surgery and compression from tumors.