Hypoglossal Nerve

Description

Sweeping anteriorly from the upper cervical region, the hypoglossal nerve (cranial nerve XII) is traced from its exit at the hypoglossal canal of the occipital bone toward the floor of the mouth in a lateral skull profile. Its course passes inferior to the angle of the mandible and deep to the submandibular region, then continues forward toward the oral cavity where it distributes motor fibers to the intrinsic and extrinsic tongue musculature. Nearby cranial and cervical nerves are rendered as yellow cords against the maxilla, mandible, nasal cavity, orbit, and external ear, with occasional blue vessels included for spatial reference. Bony landmarks, teeth, and the temporomandibular region establish depth and orientation. Clinically, this view clarifies why hypoglossal palsy produces ipsilateral tongue weakness and deviation toward the lesion on protrusion, a bedside finding that localizes motor dysfunction without needing imaging. The nerve’s relationship to the mandibular angle and submandibular space is the practical takeaway, since it is vulnerable during neck dissection, submandibular gland surgery, and airway procedures that involve deep retraction in the floor of mouth. Small mistakes here have lasting consequences. The lateral profile also supports teaching the distinction between a lower motor neuron lesion of CN XII and supranuclear involvement, where deviation patterns and associated deficits differ. Ideal use cases include cranial nerve modules in gross anatomy and neuroanatomy courses, operative anatomy figures for otolaryngology and oral and maxillofacial surgery texts, and patient-facing graphics explaining tongue weakness after carotid endarterectomy or submandibular approaches. It also fits radiology teaching when correlating the hypoglossal canal region on CT skull base studies with expected motor deficits. Anatomical accuracy verified by SciePro's Medical Advisory Board.