Fourth Ventricle

The fourth ventricle has a diamond shape and is situated immediately anteriorly to the cerebellum. The lateral walls of the fourth ventricle are made up of the cerebella peduncles. It contains a choroid plexus close to the bottom of the cerebellum. CSF drains from the third ventricle into the fourth via the cerebral aqueduct. CSF exits the fourth ventricle via several routes. The luschka foramina located in the lateral aspects of the ventricle, and the single foramen of magendie found medially allow CSF to flow into the subarachnoid space (specifically the cisterna magna). Where the fourth ventricle narrows it forms an imaginary boundary between the brain and spinal cord known as the obex.