The hypoglossal nerve is the twelfth paired cranial nerve. Its name is derived from ancient Greek, ‘hypo‘ meaning under, and ‘glossal‘ meaning tongue. The nerve has a purely somatic motor function, innervating all the extrinsic and intrinsic muscles of the tongue (except the palatoglossus, innervated by vagus nerve). In this article, we shall look at the anatomy of the hypoglossal nerve – its anatomical course, motor functions and clinical correlations. Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Anatomical Course The hypoglossal nerve arises from the hypoglossal nucleus in the medulla oblongata of the brainstem. It then passes laterally across the posterior cranial fossa, within the subarachnoid space. The nerve exits the cranium via the hypoglossal canal of the occipital bone. Now extracranial, the nerve receives a branch of the cervical plexus that conducts fibres from C1/C2 spinal nerve roots. These fibres do not combine with the hypoglossal nerve – they merely travel within its sheath. It then passes inferiorly to the angle of the mandible, crossing the internal and external carotid arteries, and moving in an anterior direction to enter the tongue. By TeachMeSeries Ltd (2025) Fig 1The extracranial anatomical course of the hypoglossal nerve Pro Feature - Dissection Images The carotid bifurcation and proximal branches of the external carotid artery. Note how the hypoglossal nerve crosses anteriorly over the external carotid artery. The carotid bifurcation and proximal branches of the external carotid artery. Note how the hypoglossal nerve crosses anteriorly over the external carotid artery. You've Discovered a Pro Feature Access our Dissection Image Library Enhance your understanding with high-resolution dissection images showcasing real-life anatomy. Learn More Motor Function The hypoglossal nerve is responsible for motor innervation of the vast majority of the muscles of the tongue (except for palatoglossus). These muscles can be subdivided into two groups: i) Extrinsic muscles Genioglossus (makes up the bulk of the tongue) Hyoglossus Styloglossus Palatoglossus (innervated by vagus nerve) ii) Intrinsic muscles Superior longitudinal Inferior longitudinal Transverse Vertical Together, these muscles are responsible for all movements of the tongue. Role of the C1/C2 Roots The C1/C2 roots that travel with the hypoglossal nerve also have a motor function. They branch off to innervate the geniohyoid (elevates the hyoid bone) and thyrohyoid (depresses the hyoid bone) muscles. Another branch containing C1/C2 fibres descends to supply the ansa cervicalis – a loop of nerves that is part of the cervical plexus. From the ansa cervicalis, nerves arise to innervate the omohyoid, sternohyoid and sternothyroid muscles. These muscles all act to depress the hyoid bone. By TeachMeSeries Ltd (2025) Fig 2Overview of the motor functions of the hypoglossal nerve Clinical Relevance Cranial Nerve Examination The hypoglossal nerve is examined by asking the patient to protrude their tongue. Other movements such as asking the patient to push their tongue against their cheek and feeling for the pressure on the opposite side of the cheek may also be used if damage is suspected. Hypoglossal Nerve Palsy Damage to the hypoglossal nerve is a relatively uncommon cranial nerve palsy. Possible causes include head & neck malignancy and penetrating traumatic injuries. If the symptoms are accompanied by acute pain, a possible cause may be dissection of the internal carotid artery. Patients will present with deviation of the tongue towards the damaged side on protrusion, as well as possible muscle wasting and fasciculations (twitching of isolated groups of muscle fibres) on the affected side. By TeachMeSeries Ltd (2025) Fig 3Right hypoglossal nerve palsy, characterised by deviation of the tongue to the right. Do you think you’re ready? Take the quiz below Pro Feature - Quiz The Hypoglossal Nerve (CN XII) Question 1 of 3 Submitting... Skip Next Rate question: You scored 0% Skipped: 0/3 1800 More Questions Available Upgrade to TeachMeAnatomy Pro Challenge yourself with over 1800 multiple-choice questions to reinforce learning Learn More Print Article Rate This Article