Hypoglossal Nerve

Description

Emerging as paired rootlets from the anterolateral sulcus of the medulla oblongata, the hypoglossal nerve (cranial nerve XII) courses anteriorly toward the hypoglossal canal and then descends into the upper neck. Within the carotid triangle it runs inferior and anterior to the posterior belly of digastric and stylohyoid, crossing lateral to the internal and then external carotid artery while remaining closely related to the internal jugular vein and vagus nerve within the carotid sheath. Distally, a descending branch forms the superior root of the ansa cervicalis (C1 fibers hitchhiking with XII), while the main trunk turns anteromedially toward the tongue to distribute to the genioglossus, hyoglossus, and styloglossus. That carotid triangle segment is the operative corridor where XII is most at risk, and this view helps you track its arc against reliable landmarks when planning neck dissection, carotid endarterectomy, or submandibular gland surgery. Hypoglossal palsy is not subtle: ipsilateral tongue weakness with deviation toward the lesion on protrusion, often accompanied by dysarthria, points you back to this course and to compressive etiologies such as carotid space tumors, traumatic intubation, or iatrogenic stretch. A clean teaching frame. Use this illustration in head and neck anatomy curricula to contrast the motor-only XII with neighboring mixed cranial nerves, or in surgical atlases and patient education materials addressing postoperative tongue weakness after carotid or parapharyngeal procedures. It also fits neuroradiology orientation discussions by pairing brainstem exit zones with expected extracranial trajectories in the upper neck. Anatomical accuracy verified by SciePro's Medical Advisory Board.