Vagus Nerve (Cranial Nerve X, C.N. X)

The 10^th cranial nerve (Cranial Nerve X, or C.N. X, using the Roman Numeral for “10”) is named “vagus,” meaning “wandering,” because of its long and diverse course through the body. The nerve originates in the lower brainstem (medulla oblongata) and sends branches to many structures on its way from base of skull all the way down to the large intestine. Some branches are motor (to muscles); some are sensory; and some are parasympathetic, helping regulate automatic functions like saliva production, heart rate, and digestion.

Our interest at Laryngopedia is primarily in the motor (and sensory) branches of C.N. X which go to palate, pharynx, and larynx musculature.

Disorders of the Vagus Nerve

The commonest dysfunction of the Vagus Nerve in laryngology practice is of the recurrent laryngeal nerve (RLN) branch of the Vagus Nerve. The result is a paralyzed or paretic vocal cord, causing a weak voice and, occasionally, coughing on liquids. RLN injury can be due to viral injury, thyroidectomy, cervical spine surgery, penetrating or crush trauma, and tumors of the neck, upper lobes of the lung, esophagus,or enlarged lymph nodes in the mediastinum (central chest).

Much less common Vagus Nerve dysfunction may be caused by lesions (tumors, trauma, primarily) very high in the neck, and affecting nerve near its brain stem origin. That sort of injury would be above (and therefore affect) branches to palate, pharynx, and larynx, and cause drooping (failure to elevate) of the palate, paralysis of the pharynx on the affected side, and paralysis of the vocal cord.

Symptoms

The functional result of a high lesion would be:

• Hypernasal speech and potentially nasal regurgitation while swallowing (palate branch);
• Difficulty swallowing due to retained material in the lower throat, aka hypopharynx (pharyngeal branch);
• And a weak, breathy voice (recurrent laryngeal nerve branch).

In summary, the Vagus Nerve branches to the palate, pharynx, and larynx provide motor and sensory innervation to these structures.

Vagus Nerve Damage Near Base of Skull, With Paralysis of Left Palate, Pharynx, and Larynx

This middle-aged man suddenly developed hypernasal speech, difficulty swallowing, and a weak and breathy voice.  CT scanning did not show any mass lesion along the course of the Vagus Nerve, and the assumption is that this is a post-viral neuropathy (like Bell’s Palsy by analogy). The result of this high Vagus Nerve injury is lost elevation of the palate, pharyngeal weakness, and a paralyzed vocal cord, explaining the above functional changes.

High Vagus Nerve Injury

The vagus (10^th cranial) nerve originates from the medulla (part of the brainstem), exits from the base of the skull through the jugular foramen, and among other things, supplies branches to the musculature of palate, pharynx, and larynx. Location of vagus nerve injury is sometimes evident by palate and pharynx findings. But these findings are sometimes overlooked as in this case, especially if palate and pharynx are weak but not completely paralyzed.

Case study: This 50-something woman developed a weak voice and moderate difficulty swallowing upon awakening 5 months prior to this visit. Fortunately, her symptoms of weak voice and difficulty swallowing were not devastating, and are improving. But up to this examination, there has been no diagnosis. This examination reveals a “lesion” of her right vagus nerve and it has to be at the base of the skull because palate, pharynx, and larynx muscles are all weak. Voice is functional but lacks the ability to project and has a “soft-edged” quality. A sophisticated listener can also hear mild hypernasality. The examination below prompts a scan with special attention to base of skull to be sure there is no mass lesion there.

Skull Base Fracture and Vagus Nerve Injury—Note Pharynx Contraction and Impact on Swallowing