Cerebrospinal fluid (CSF) is a clear, watery liquid that flows around the brain and spinal cord, surrounding and protecting them. CSF testing is performed to evaluate the level or concentration of different substances and cells in CSF in order to diagnose conditions affecting the brain and spinal cord (central nervous system).
The appearance of the sample of CSF is usually compared to a sample of water.
Color of the fluid - normal is clear and colorless. Changes in the color of the CSF are not diagnostic but may point to additional substances in the fluid. Yellow, orange, or pink CSF may indicate the breakdown of blood cells due to bleeding into the CSF or the presence of bilirubin. Green CSF may also sometimes be seen with bilirubin or infection.
Turbidity - cloudy or turbid CSF may indicate the presence of white or red blood cells, microbes, or an increase in protein levels.
Viscosity - normal CSF will have the same consistency as water. CSF that is “thicker” may be seen in people with certain types of cancers or meningitis.
Conditions associated with changes in the appearance of CSF include the following:
Infectious meningitis – Turbid, milky, cloudy CSF samples
Hemorrhage or traumatic tap – Xanthochromic CSF samples with increased hemoglobin
Kernicterus - Xanthochromic CSF samples with increased bilirubin
Meningeal melanosarcoma – Xanthochromic CSF samples with increased melanin
Disorders affecting blood-brain barrier - Cloudy CSF samples with increased proteins (above 150 mg/dL) and albumin and IgG
Xanthochromia is the term used for any kind of discoloration of CSF (pink, yellow, orange).
Multiple conditions are associated with xanthochromia:
traumatic tap, presence of carotene, melanoma and increased bilirubin concentration (bilirubin concentration will also be elevated in serum and patients are often jaundiced) due to liver diseases, hemolytic diseases (also increased free hemoglobin concentration) and inborn errors of metabolism.
Note that normal CSF samples should be colorless, clear, like water. If CSF samples are centrifuged immediately, xanthochromia due to traumatic tap should not occur. However, if CSF samples are carefully centrifuged immediately and the supernatant is still xanthochromic, this indicates that bleeding may have occurred 2-4 hours before sample collection. Furthermore, in about 10% of patients with subarachnoid hemorrhage, the CSF samples might be clear if the samples are collected 12 hours after the hemorrhage occurred.
Typically, high levels of oxyhemoglobin occur in CSF fluid obtained through a traumatic lumbar puncture, in which red blood cells enter the subarachnoid space via direct needle puncture. This frustrates the ability to determine whether xanthochromia, and thus subarachnoid hemorrhage, is present.
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