Vagus Nerve (CN X)

The vagus nerve is the tenth cranial nerve and the longest of all cranial nerves, wandering from the brainstem to the abdomen (vagus means "wandering" in Latin). It is the primary parasympathetic nerve, regulating heart rate, digestion, and numerous visceral functions.

Origin

Motor: nucleus ambiguus; Sensory: superior (jugular) and inferior (nodose) ganglia; Parasympathetic: dorsal motor nucleus

Foramina

Jugular foramen

Course

Exits lateral medulla → jugular foramen → descends in carotid sheath → thorax alongside esophagus → abdomen (anterior and posterior vagal trunks)

Functions

•Parasympathetic to thoracic and abdominal viscera
•Heart rate reduction
•Bronchial constriction
•GI motility and secretion
•Voice production (laryngeal muscles)
•Swallowing (pharyngeal muscles)
•Taste from epiglottis
•Efferent limb of gag and cough reflexes

Branches

Pharyngeal branches

Superior laryngeal nerve (external and internal)

Recurrent laryngeal nerve

Cardiac branches

Pulmonary branches

Esophageal plexus

Gastric branches

Structures Innervated

→Pharyngeal muscles (except stylopharyngeus)
→Laryngeal muscles (all intrinsic)
→Heart
→Lungs
→GI tract to splenic flexure
→Sensation: larynx, pharynx, external ear

Clinical Testing

Assess voice quality (hoarseness). Watch palate elevation ("ah") - uvula deviates away from lesion. Test gag reflex (X efferent). Check cough reflex.

Clinical Relevance

Recurrent laryngeal nerve palsy causes hoarseness (unilateral) or airway compromise (bilateral). Left RLN loops under aortic arch, vulnerable in thoracic surgery and lung cancer. Vagal tone abnormalities contribute to cardiac arrhythmias.

Study Tips

✓"Vagus" = wandering, supplies everything from neck to splenic flexure
✓Left recurrent laryngeal loops under aortic arch - longer course, more vulnerable
✓Uvula deviates AWAY from CN X lesion (pulled by intact side)
✓All laryngeal muscles by recurrent laryngeal EXCEPT cricothyroid (external laryngeal)

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Vagus Nerve (CN X) FAQs

Common questions about this cranial nerve

The left RLN has a longer course, looping under the aortic arch before ascending. This makes it vulnerable to aortic aneurysm, mediastinal tumors, lung cancer, and cardiac surgery. The right RLN loops under the subclavian artery, a shorter path.

Bilateral RLN palsy causes both vocal cords to assume a paramedian position. This severely compromises the airway, causing stridor and potentially requiring emergency tracheostomy. It can occur after thyroid surgery or bilateral neck trauma.

Vasovagal syncope is fainting caused by an exaggerated vagal response to triggers like prolonged standing, pain, or emotional stress. The vagus nerve slows heart rate and dilates blood vessels, reducing brain perfusion and causing loss of consciousness.