Cerebrospinal Fluid Protein

The cerebrospinal fluid (spinal fluid, CSF) is a clear, colorless fluid that fills the nontissue spaces of the brain and spinal cord. The fluid serves to maintain constancy of intracranial pressure and to provide a mechanical, water jacket type of protective coating for the delicate nerve tissue. It is formed as a secretion by cells in the cerebral ventricles. The total volume is about 150 ml. The fluid is a slightly modified ultrafiltrate of plasma. Its composition varies slightly, depending on where it is sampled. There is a gradual change in concentration of its components as the fluid flows down from the brain ventricles to the cisternal space and then to the lumbar area of the spinal cord, where the usual laboratory spinal fluid specimen is obtained by means of a spinal needle puncture.

Normally, a spinal puncture will supply a 6 to 10 ml. specimen. Because of the effort and skill demanded in obtaining good specimens and because of the trauma to the patient, repeat punctures are to be avoided. Spinal fluids are, therefore, very precious specimens; they are handled carefully to avoid loss and every effort is made to get as much information as possible from the volume of sample available. Any leftover portion is stored refrigerated or frozen for 7 to 10 days for possible repeat determinations or for other tests that might be dictated by the clinical status of the patient.