Cerebrospinal fluid (CSF) normally flows around the brain and through the spinal cord following a standard physiological pattern of circulation. It starts in the brain, where it is taken from the bloodstream and membranes, then cerebrospinal fluid flow proceeds along established paths through the cranium, cranial nerves, and spine. This flow is influenced by gravitational fields as well as by the pressure of the circulating bloodstream. Medical professionals can monitor the flow paths of cerebrospinal fluid by using magnetic resonance imaging (MRI) studies of patients' brains.

Cerebrospinal fluid flow begins in the high midbrain area from within the lateral ventricles. The fluid is pulled from the bloodstream and membranes of the brain by areas in the cerebral ventricles and brainstem called the choroid plexus. CSF then flows down into the third ventricle, where more of the fluid is produced, adding to the flow volume. The fluid then drains down into the fourth ventricle through a space called the Aqueduct of Sylvius. Some CSF is also produced in the fourth ventricle, but this fluid takes another path away from the main flow and goes directly down to the cisterna magna, a large basin-shaped area at the bottom of the skull.

The main volume of the cerebrospinal fluid flow then goes down into the subarachnoid space and out through openings called cisterna into other parts of the brain and into the spinal column. The largest opening is called the cisterna magna. This is where the main volume of the CSF flow meets up with the CSF that was produced in the fourth ventricle.

Cerebrospinal fluid flow goes through the cisterna magna and down into the spine. It returns to the brain in the area of the superior sagittal sinus, a groove along the top of the skull that runs from the front of the head to the back. Here, the CSF is then reabsorbed into the bloodstream by the arachnoid villi, which are spongy tissues found in this region.

The flow of cerebrospinal fluid can be seen by an MRI. Such studies have shown that if CSF pressure is higher than that of the veins into which it is being absorbed — the blood pressure — then it will be absorbed back into the bloodstream. The rate at which CSF is absorbed depends upon the venous pressure.

If the pressure of the CSF is much lower than the venous pressure, however, it cannot be reabsorbed back into the bloodstream. This can lead to blockages, which may have serious health effects. Medical professionals have installed CSF shunts to alleviate this condition, and to help regulate CSF flow again within the body.

CSF flow can be altered by changes in gravitational fields. For example, being suspended head-down above the earth at any distance would be a gravitational influence upon CSF flow. The fields produced by standard MRIs are magnetic fields, which differ from the gravitational field influences of a large planetary mass, and do not affect the cerebrospinal fluid flow in the same way.