Brainstem's Pons, Posterior View

Description

Pons and adjacent brainstem landmarks dominate the posterior aspect of the rhomboid fossa, where the dorsal pontine surface forms the superior portion of the floor of the fourth ventricle. Along the midline, the median sulcus separates paired medial eminences, and the facial colliculi sit paramedian where the internal genu of the facial nerve (CN VII) loops over the abducens nucleus (CN VI). Lateral to this, the sulcus limitans and its superior fovea define the transition toward the vestibular area, while the striae medullares of the fourth ventricle course transversely across the floor at the pontomedullary level. The dorsal pons meets the superior medullary velum and the cerebellar peduncles at the rostral margin of the ventricle. These surface contours matter because they map directly to nuclei and fiber tracts that neurosurgeons and neurologists localize at the bedside and in the operating room. A small lesion centered on the facial colliculus can produce the classic combination of ipsilateral horizontal gaze palsy and facial weakness, and dorsal pontine infarcts or hemorrhage often declare themselves with abducens, facial, and vestibular signs. The fixed posterior perspective is also the one used when discussing safe entry zones to the fourth ventricle floor, where millimeters separate ependymal surface from the pontine tegmentum. Neuroanatomy instructors can use this illustration to teach the topography of the fourth ventricle floor in lab or lecture, and authors of neurology and neurosurgery texts can pair it with discussions of dorsal pontine syndromes, telovelar suboccipital approaches, and intrinsic brainstem tumors that abut the ventricular surface. Radiology educators will also find it useful for correlating MRI of the fourth ventricle and dorsal pons with named landmarks on the rhomboid fossa. Anatomical accuracy verified by SciePro's Medical Advisory Board.