What is the vagus nerve and what is its primary function?

The vagus nerve (cranial nerve X) is the longest and most widely distributed cranial nerve, extending from the head and neck into the thorax and abdomen. It is a mixed nerve with predominantly motor fibers, carrying most parasympathetic efferents to regulate organs like the heart, lungs, and gastrointestinal tract.

What are the functional components of the vagus nerve?

The vagus nerve has multiple functional components: Motor fibers for muscles of the palate, pharynx, and larynx (SVE). Parasympathetic fibers to the heart, lungs, and GI tract (GVE). Sensory fibers for taste from the epiglottis and posterior tongue (SVA), and general sensation from viscera and skin (GVA and GSA).

Where does the vagus nerve originate and what is its course?

It arises from rootlets in the lateral medulla and exits the skull via the jugular foramen. In the neck, it descends within the carotid sheath between the internal jugular vein and carotid artery, then extends into the thorax and abdomen.

What are the key branches of the vagus nerve and what do they supply?

Key branches include: Pharyngeal branch for pharyngeal muscles and soft palate. Superior laryngeal nerve with motor and sensory parts for the larynx and pharynx. Recurrent laryngeal nerve for intrinsic laryngeal muscles and sensation below the vocal cords. Auricular branch for skin of the external ear and auditory canal.

What happens if the vagus nerve is damaged?

Bilateral lesions can cause symptoms like nasal regurgitation, hoarseness, vocal cord paralysis, dysphagia, and loss of the cough reflex. Unilateral damage may lead to palatal droop and uvula deviation away from the lesion during clinical testing.

How is the vagus nerve tested clinically?

A common test involves having the patient say "ah" to observe soft palate elevation. Intact vagus function results in symmetric elevation, while a unilateral lesion causes the uvula to deviate away from the affected side.

What is Alderman's nerve phenomenon related to the vagus nerve?

Alderman's nerve refers to the auricular branch of the vagus nerve. Historically, stimulation of this branch was known to increase gastric motility and appetite, a phenomenon used by Roman Aldermen.

Vagus Nerve (CN X) – Course, Branches & Parasympathetic

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