Cranial Nerve XII: Hypoglossal Nerve

00:00 The last cranial nerve for your consideration is that of the hypoglossal nerve, cranial nerve number XII.

00:08 It only has one functional component and that is general somatic efferent, so it has motor control.

00:15 This nerve is transmitted through the hypoglossal canal.

00:18 The general somatic efferent functional component is going to innervate the hyoglossus muscle that runs from the hyoid bone to the tongue which is now highlighted in red. The genioglossus running from the genio, the mandible to the tongue, styloglossus running from the styloid process to the tongue, now shaded in red. Then the intrinsic tongue musculature is also going to be innervated by the hypoglossal nerve.

00:55 Now, that is shaded in red for you. Clinical considerations for you to remember about the hypoglossal nerve would be that injury to this nerve would cause difficulty with speech. The skeletal muscle of the same side would atrophy, so atrophy of ipsilateral tongue musculature because of the lack of innervation.

01:23 Then there would be deviation of the tongue toward the affected side upon protrusion by the patient.

01:33 Causes of clinical considerations would be a tumor involving the nerve, an infarction, lack of blood supply, infection is always a consideration here, neck injury that’s in the right location, and amyotrophic lateral sclerosis, ALS is another consideration in producing the symptoms.