Nerve · Neck

Superior laryngeal nerve

Nervus laryngeus superior

The vagus nerve's branch to the upper half of the voice box. It leaves the vagus just below the skull base, descends beside the throat, and splits in two: a stout internal branch that pierces the thyrohyoid membrane to carry sensation from the larynx above the vocal folds, and a slender external branch that runs on the inferior pharyngeal constrictor alongside the superior thyroid artery to reach cricothyroid — the only muscle that tenses the vocal cords. That division of labour is unusual: one nerve, one sensory territory and one muscle. The internal branch is the sensory limb of the cough reflex, which is why the larynx objects so violently when food takes the wrong turn.