What normally happens with CSF in the brain?
Normally, cerebrospinal fluid is produced in the lateral ventricles by a specialized tissue called the Choroid Plexus. It flows out of these ventricles through a passage called the Foramen of Monroe and into the third ventricle. From here the fluid passes through the Aqueduct of Sylvius into the fourth ventricle. The CSF leaves the fourth ventricle by passing through three foramens or openings into the subarachnoid space which surrounds both the brain and the spinal cord. Once in the subarachnoid space, most of the CSF is absorbed at the top and midline of the brain through specialized cell clusters (arachnoid villi) that pass the fluid into a large vein called the sagittal sinus. It is here that the CSF enters into and mixes with the blood stream. The CSF that passes along the outside of the spinal cord is ultimately absorbed by the lymph system. This is also the fate of a small amount of CSF that passes directly into and through the brain itself. The system of fluid production and re
