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Cranial nerves · Mixed

X. Vagus nerve

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The vagus nerve (CN X) is the longest cranial nerve. It supplies the pharynx and larynx and provides most of the parasympathetic innervation of the thoracic and abdominal viscera as far as the left colic flexure (the distal colon is supplied by the sacral outflow).

Terminologia Anatomica (Latin): Nervus vagus

Function

Special visceral efferent to the muscles of the palate (except tensor veli palatini), pharynx and larynx. General visceral efferent (parasympathetic) to the heart, lungs and gut. General and special visceral afferent from the viscera and the epiglottic taste buds, and general somatic afferent from the external ear and meninges.

Nuclei

Nucleus ambiguus (motor to pharynx and larynx, and cardiac parasympathetic neurons), dorsal motor nucleus of the vagus (parasympathetic to thoracic and abdominal viscera), nucleus of the solitary tract (visceral afferents and taste), and the spinal trigeminal nucleus (somatic sensation).

Exit from the skull

It leaves the skull through the jugular foramen, descends in the carotid sheath, and passes through the thorax and the oesophageal hiatus of the diaphragm into the abdomen. The right recurrent laryngeal nerve loops around the right subclavian artery, the left around the aortic arch, then both ascend in the tracheo-oesophageal groove.

Testing

Ask the patient to say 'ah' and watch the soft palate rise symmetrically with the uvula in the midline, assess voice quality (hoarseness) and cough, and test swallowing. Laryngoscopy is needed to assess vocal cord movement.

Signs of a lesion

A unilateral lesion causes the soft palate to droop on the affected side and the uvula to deviate away from the lesion toward the normal side on phonation, with hoarseness, dysphagia and a weak cough. Recurrent laryngeal nerve injury causes hoarseness from vocal cord paralysis; bilateral injury may cause stridor and airway compromise.

Clinical correlations

The recurrent laryngeal nerve can be injured in thyroid and parathyroid surgery, by aortic arch aneurysm or mediastinal and apical lung tumours (the left nerve is longer and more exposed to mediastinal disease). Vagal stimulation can cause bradycardia and syncope (vasovagal reflex). Vagotomy was historically used for peptic ulcer disease.

Common exam points

  • Exits via the jugular foramen; supplies the viscera to the left colic flexure.
  • Uvula deviates away from the side of a vagal lesion.
  • Recurrent laryngeal nerve: right loops under the subclavian artery, left under the aortic arch; at risk in thyroid surgery.
  • Efferent limb of the gag and cough reflexes; parasympathetic slowing of the heart.
  • Dorsal motor nucleus (parasympathetic), nucleus ambiguus (branchial motor).

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Haines DE, Mihailoff GA. Fundamental Neuroscience for Basic and Clinical Applications. Elsevier, 5th edition (2018) — Tier 3 (textbook)
  4. Bickley LS. Bates' Guide to Physical Examination and History Taking (Bickley). Wolters Kluwer, 13th edition (2020) — Tier 3 (textbook)

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