Median Sulcus Of The Rhomboid Fossa Of The Brainstem

Description

Median sulcus runs in the midline of the rhomboid fossa, forming a vertical groove along the floor of the fourth ventricle over the dorsal pons superiorly and the open medulla inferiorly. On either side, the medial eminence rises immediately lateral to the sulcus, separated from the more lateral vestibular area by the sulcus limitans. Superiorly, paired facial colliculi create rounded elevations in the pontine part of the fossa, while inferiorly the hypoglossal trigone and vagal trigone are positioned medial and lateral, respectively, with the striae medullares crossing transversely near the pontomedullary junction. Midline anatomy is the organizing theme. Neurosurgeons and neuroradiologists rely on these dorsal brainstem landmarks when orienting to lesions that enter the fourth ventricle, including ependymoma, subependymoma, and dorsal exophytic tumors arising from the medulla or pons. The median sulcus provides a fixed reference for judging laterality, helping correlate a focal bulge or distortion of the ventricular floor with expected cranial nerve nuclei and fiber pathways beneath the ependyma, a practical concern during telovelar approaches and when counseling risk of postoperative deficits such as facial weakness, dysphagia, or gaze palsy. Depth and shadowing along the sulcus edges make the midline groove easy to separate from adjacent elevations. Use this illustration in neuroanatomy teaching on the fourth ventricle and brainstem surface anatomy, in operative atlases describing dorsal approaches to the pons and medulla, or in review figures for case reports that localize pathology to the rhomboid fossa by surface topography. It also pairs well with MRI correlation pages that teach readers how ventricular floor landmarks map to clinical syndromes. Anatomical accuracy verified by SciePro's Medical Advisory Board.