Vagus nerve: A nerve that supplies nerve fibers to the pharynx (throat), larynx (voice box), trachea (windpipe), lungs, heart, esophagus, and intestinal tract, as far as the transverse portion of the colon. The vagus nerve also brings sensory information back to the brain from the ear, tongue, pharynx, and larynx. The vagus nerve is the tenth cranial nerve. It originates in the medulla oblongata, a part of the brain stem, and extends all the way down from the brain stem to the colon. Complete interruption of the vagus nerve causes a characteristic syndrome in which the soft palate droops on the side where damage occurred, and the gag reflex is also lost on that side. The voice is hoarse and nasal, and the vocal cord on the affected side is immobile. The result is difficulty swallowing (dysphagia) and speaking (dysphonia). The vagus nerve has several important branches, including the recurrent laryngeal nerve.