Hypoglossal Nerve

Description

Inferior brain anatomy is rendered from the basal aspect, centering on the hypoglossal nerve (cranial nerve XII) emerging as multiple rootlets from the anterolateral sulcus of the medulla oblongata, just superior to the pyramids and medial to the olive. Each XII rootlet converges and courses anterolaterally toward the hypoglossal canal, while the vagus nerve (cranial nerve X) exits more posterolaterally from the postolivary sulcus, placing X inferior and lateral to XII at the level of the medullary surface. The pons and midbrain sit superior to the medulla, and the remaining cranial nerves are traced anteriorly and laterally across the basal brain in standard anatomical position. Orientation is unambiguous. For teaching brainstem surface anatomy, the relationship between the preolivary and postolivary sulci is the point, it lets you localize lower cranial nerve nuclei and predict deficits from lateral medullary versus medial medullary lesions. Hypoglossal dysfunction produces ipsilateral tongue weakness with deviation toward the lesion on protrusion, a bedside sign that helps distinguish a medial medullary infarct (often involving the anterior spinal artery territory) from Wallenberg syndrome, where nucleus ambiguus involvement drives dysphagia and hoarseness without a primary XII palsy. Surgeons and trainees also use this inferior view to anticipate where XII lies relative to X during approaches to the jugular foramen and upper cervical carotid space. Neurology and neuroanatomy courses can pair this plate with brainstem cross-sections to connect external landmarks to nuclei, tracts, and stroke syndromes, while head and neck surgery texts can reference it when describing hypoglossal canal anatomy and lower cranial nerve risk during skull base exposure. It also supports clinical documentation and patient education around hypoglossal neuropathy after intubation, carotid endarterectomy, or neck dissection. Anatomical accuracy verified by SciePro's Medical Advisory Board.