Anterolateral Sulcus Of The Medulla Oblongata Of The Brainstem

Description

Anterolateral sulcus of the medulla oblongata is highlighted as a shallow longitudinal groove on the ventrolateral surface of the myelencephalon, immediately anterior to the olivary eminence (inferior olivary prominence). Along this sulcus, multiple hypoglossal nerve (CN XII) rootlets emerge in a vertical series, positioned medial to the olive and lateral to the medullary pyramid. Superiorly the region approaches the pontomedullary junction, while inferiorly it continues toward the cervicomedullary transition, where surface landmarks begin to blend with upper cervical cord contours. Rootlet spacing is easy to appreciate. Clinically, the preolivary (anterolateral) sulcus is the key external landmark for localizing CN XII at its brainstem exit before the nerve courses toward the hypoglossal canal, and it helps separate hypoglossal-related deficits from vagal and glossopharyngeal involvement that arises posterior to the olive at the postolivary sulcus. This surface anatomy matters when correlating lower cranial nerve palsies with medial medullary infarction (often involving anterior spinal artery territory) versus lateral medullary syndromes, and when planning far-lateral or transcondylar exposures where the surgeon must keep the hypoglossal rootlets and adjacent vertebral artery segment oriented in a fixed anterolateral field. Crisp separation between pyramid, olive, and sulcus supports confident teaching of brainstem topography. Use this illustration in neuroanatomy and head and neck courses, in stroke localization teaching files, and in operative atlases discussing approaches to the ventrolateral medulla and hypoglossal canal region. Anatomical accuracy verified by SciePro's Medical Advisory Board.