Morphological Features of the Branching Pattern of the Hypoglossal Nerve

The hypoglossal or twelfth cranial nerve is the motor nerve to the extrinsic and intrinsic muscles of the tongue, and the superior root of the ansa cervicalis and the thyrohyoid and geniohyoid branches are delivered through the nerve. This study investigated the muscular branches of the hypoglossal nerve to clarify their spatial relationships with the muscles of the tongue and the neighboring structures. The muscles and the nerve were gross anatomically examined in 42 cadavers. The superior root and the thyrohyoid branch left the nerve near the occipital and lingual arteries, respectively. The extrinsic muscles consisted of some components, and the geniohyoid branch and the lingual branches arose on the hyoglossus. The ascending lingual branches formed a plexus on the anterior part of the hyoglossus and were divided into the proximal and distal groups. They supplied the two parts of the hyoglossus, the three bundles of the styloglossus and the superior and inferior longitudinal muscles and communicated with the lingual nerve. The descending lingual branches supplied the inferior part of the genioglossus, and the terminal branches gave intramuscular twigs to its main part and the transverse and vertical muscles. The findings indicated that the branching pattern of the hypoglossal nerve is characterized by the positional relationships to the components of the extrinsic muscles. The hyoid bone can be an effective marker to identify the branches and affected position if it was used in combination with the morphology of the extrinsic muscles, and the knowledge of their variations is also beneficial. Anat Rec, 302:558-567, 2019. © 2018 Wiley Periodicals, Inc.