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Identify the hypoglossal nerve (CN XII) just superior to the greater horn of the hyoid bone. Follow the nerve proximally and confirm that it lies medial to the posterior belly of the digastric muscle, and passes lateral to the internal and external carotid arteries. Confirm also that the hypoglossal nerve loops under the occipital artery.Identify the superior root of the ansa cervicalis (descendens hypoglossi) as it descends into the anterior triangle on the surface of the carotid sheath (Figure 25.3). The superior root is composed mainly of fibers of C1, which accompany the hypoglossal nerve into the neck. Fibers from C1 course along the hypoglossal nerve
and then branch off independently to the genohyoid muscle and thyrohyoid muscle (nerve to the thyrohyoid muscle).
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