Xanthochromia

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Xanthochromia is the yellowish color that can appear in cerebrospinal fluid (CSF) several hours after bleeding into the area around the brain. It most often happens with subarachnoid hemorrhage, usually from a ruptured brain aneurysm. Normal CSF is clear and colorless.

When bleeding starts, the CSF may look bloody or tinged with blood. After a few hours, the red blood cells break down and create bilirubin, a yellow pigment, giving the CSF its yellow color.

How it’s tested
- The first test for suspected subarachnoid hemorrhage is a CT scan of the head. CT is very good in the first 12 hours but misses some cases as time passes.
- If the CT scan is normal but SAH is still suspected, a lumbar puncture (spinal tap) is done to examine the CSF for blood and for xanthochromia.

How xanthochromia is detected
- Visual inspection: Many labs look at the color of the CSF to decide if xanthochromia is present.
- Spectrophotometry: This test measures how the CSF absorbs light. It can detect bilirubin (which absorbs light at certain wavelengths) and other pigments, and can pick up very small amounts of yellow color that visual inspection might miss. It may also help identify other substances.

Who uses which method
- Visual inspection is common in the United States.
- Spectrophotometry is used in many laboratories in the United Kingdom.
- There’s ongoing debate about whether spectrophotometry should be used routinely or if visual inspection is enough.

Important nuances
- If the CSF is bloody from a traumatic tap (the needle caused bleeding), those red blood cells haven’t had time to break down into bilirubin, so xanthochromia would not be present.
- A very clear CSF with no blood after a lumbar puncture makes xanthochromia unlikely.
- The concept of xanthochromia dates back to 1902.