Cerebrospinal fluid is produced mainly in the choroid plexus of the cerebral ventricles, with 90% of it arising in the choroid plexus of the lateral ventricles. Cerebrospinal fluid fills the skull of the organism, enters the individual ventricles through the holes and gaps between the ventricles, and enters the subarachnoid space of the spine through the foramen magnum of the occipital bone. Thus, the entire circulation of cerebrospinal fluid is from the lateral ventricles to the various ventricles of the skull, then down through the foramen magnum to the subarachnoid space of the spine, nourishing the vast majority of the body’s brain tissue and spinal cord. There is a certain pressure in the cerebrospinal fluid, and if some diseases cause impaired circulation and flow of cerebrospinal fluid, resulting in increased intracranial pressure, patients can experience headache, nausea, vomiting and other symptoms.