From the Guidelines
In a subarachnoid hemorrhage, cerebrospinal fluid (CSF) obtained through lumbar puncture is typically xanthochromic (yellow) rather than clear, as evidenced by the high sensitivity and specificity of xanthochromia evaluation in diagnosing SAH 1. The yellow discoloration of CSF in SAH develops several hours after the hemorrhage occurs, usually becoming evident 2-12 hours after bleeding and persisting for up to two weeks.
- The progression to xanthochromia is a time-dependent process, which is why timing of the lumbar puncture is important in diagnosis.
- If a lumbar puncture is performed too early after symptom onset (less than 12 hours), xanthochromia might not yet be present.
- The yellow color results from the breakdown of red blood cells in the CSF, specifically the conversion of hemoglobin to bilirubin.
- Initially after a subarachnoid hemorrhage, the CSF may appear frankly bloody rather than yellow. This yellow discoloration of the CSF is a key diagnostic finding that helps differentiate a true subarachnoid hemorrhage from a traumatic tap, where blood enters the CSF during the procedure itself rather than from a pre-existing bleed, as supported by the American Heart Association/American Stroke Association guideline for the management of patients with aneurysmal subarachnoid hemorrhage 1.
From the Research
Cerebrospinal Fluid Color in Subarachnoid Hemorrhage
- The color of cerebrospinal fluid (CSF) in a lumbar puncture (LP) with a subarachnoid hemorrhage (SAH) can be an important diagnostic indicator 2, 3, 4.
- Xanthochromia, a yellow discoloration of the CSF resulting from hemoglobin catabolism, is often critical in making a diagnosis of SAH 2.
- The presence of xanthochromia can be detected through visual inspection or spectrophotometric analysis of the CSF 3, 4.
- A study found that the sensitivity of CSF xanthochromia in identifying patients with aneurysmal subarachnoid hemorrhage (aSAH) was 100% when combined with a CSF red blood cell count greater than 2000 × 10(6)/L 4.
Diagnostic Considerations
- The timing of the LP in relation to the onset of the SAH can affect the results of the CSF analysis, with the typical findings changing over time 2.
- The "three tube test", opening pressure, and inspection for visual xanthochromia are essential methods for distinguishing traumatic LP from true SAH 2.
- Computed tomography (CT) of the cerebrum is the diagnostic method of choice for SAH, but lumbar puncture with spectrophotometric analysis of CSF for xanthochromia can be performed in cases with strong suspicion of SAH and negative CT findings 3.