Vagus nerve (X)

At a glance

English

Vagus nerve (X)

Latin (TA2)

Nervus vagus (X)

System

Nerve

Region

Head

Side

Paired, left and right

About the vagus nerve (x)

Cranial nerve X is the longest of the cranial nerves and the main parasympathetic nerve of the body; its Latin name means 'wandering'. It is a mixed nerve, and most of its fibres are afferent, reporting on the condition of the organs back to the brainstem.

A row of rootlets leaves the medulla in the groove behind the olive, in front of the inferior cerebellar peduncle. The nerve passes out of the skull through the jugular foramen, where it bears a small superior ganglion and, just below, the larger inferior (nodose) ganglion that holds most visceral sensory cell bodies. In the neck it runs down within the carotid sheath, between and behind the internal jugular vein and the carotid arteries. The right vagus crosses in front of the right subclavian artery, passes behind the superior vena cava and the right main bronchus; the left enters the chest between the left common carotid and subclavian arteries and runs over the aortic arch. Each joins the cardiac and pulmonary plexuses, then the oesophageal plexus, which regroups as the anterior (mainly left) and posterior (mainly right) vagal trunks passing through the oesophageal hiatus.

The recurrent laryngeal nerve hooks under the right subclavian artery on the right and under the aortic arch, beside the ligamentum arteriosum, on the left, then climbs between trachea and oesophagus to the larynx. Four medullary nuclei serve it: the dorsal motor nucleus for visceral parasympathetic output, the nucleus ambiguus for the muscles of palate, pharynx and larynx and for cardiac fibres, the solitary nucleus for taste and visceral afferents, and the spinal trigeminal nucleus for skin of the ear canal and dura of the posterior fossa.

The vagus slows the heart, acting on the sinoatrial node chiefly from the right and on the atrioventricular node chiefly from the left. It drives gut movement and secretion down to about two-thirds of the way along the transverse colon and signals fullness after eating. Atropine blocks its effects and speeds the heart, while vagal manoeuvres such as breath-holding or cold water on the face can stop some fast heart rhythms. Overactivity causes vasovagal fainting. Injury to the recurrent laryngeal nerve, for example in thyroid surgery, causes hoarseness. An implanted stimulator on the cervical vagus is used for drug-resistant epilepsy and depression.

Course and supply

Arises from

Rootlets from the medulla in the posterolateral sulcus, behind the olive, drawing on the dorsal motor nucleus, nucleus ambiguus, solitary nucleus and spinal trigeminal nucleus.

Ends in

Leaves by the jugular foramen and ends as the anterior and posterior vagal trunks, whose branches spread over the stomach, liver, coeliac plexus and gut as far as the distal third of the transverse colon.

Supplies

Parasympathetic motor to the heart, lungs and gut; motor to the muscles of the palate, pharynx and larynx; sensory from the viscera, larynx, pharynx, ear canal and posterior dura; taste from the epiglottis region.