Fourth Ventricle

The fourth ventricle is a roughly pyramid-shaped space that forms the cavity of the metencephalon and myelencephalon. The apex of this ventricle extends into the base of the cerebellum, and caudally it tapers to a narrow channel that continues into the cervical spinal cord as the central canal. Laterally the fourth ventricle extends over the surface of the medulla as the lateral recesses, eventually to open into the area of the pons-medulla-cerebellum junction, the cerebellopontine angle, through the foramina of Luschka. The irregularly shaped foramen of Magendie is located in the caudal sloping roof of the ventricle. Although the roof of the caudal part of the fourth ventricle and the lateral recesses is composed of tela choroidea, the rostral boundaries of this space are formed by brain structures. These include the cerebellum (covering about the middle third of the ventricle) and the superior cerebellar peduncles and anterior medullary velum (covering the rostral third of the ventricle). The floor of the fourth ventricle, the rhomboid fossa, is formed by the pons and medulla. The only openings between the ventricles of the brain and the subarachnoid space surrounding the brain are the foramina of Luschka and Magendie in the fourth ventricle.