Sagittal view of fourth ventricle. The fourth ventricle is located between the posterior surfaces of the pons and medulla anteriorly and the vermis of the cerebellum posteriorly. The superior medullary velum is a thin lamina of white matter that stretches between the paired superior cerebellar peduncles and together they form the upper part of the roof of the fourth ventricle. The inferior medullary velum is a thin membrane that forms the inferior part of the ventricle roof.  A prominent tuft of choroid plexus is suspended from the undersurface of the inferior medullary velum and extends anteriorly and laterally on both sides, through the lateral recesses, to enter the foramina of Luschka. The latter are paired, tunnel-like openings that curve anteriorly around the brainstem to connect the midline fourth ventricle with the cerebellomedullary cistern or cisterna magna. The posterior inferior cerebellar artery, a branch of the vertebral artery, is visible on the surface of the cerebellum. The medial (and lateral) supratonsillar veins pass, respectively, along the medial and lateral edge of the inferior medullary velum and empty into the vein of the cerebellomedullary fissure. (Image courtesy of PA Rubino)