xanthochromia

Xanthochromia refers to a yellow coloration of cerebrospinal fluid (CSF) resulting from the breakdown of red blood cells within the subarachnoid space and the subsequent formation of hemoglobin breakdown products, including bilirubin. It is most commonly discussed in the context of suspected subarachnoid hemorrhage (SAH) and is an important diagnostic clue when evaluating CSF.

The appearance of xanthochromia follows bleeding into the subarachnoid space. Red blood cells in CSF lyse over time, and bilirubin accumulation leads to a yellow tint. Visually, xanthochromia may become evident several hours after the onset of bleeding, often peaking within the first day or two and potentially persisting for days to weeks. The absence of visible yellow discoloration does not definitively exclude SAH, especially in small bleeds or when samples are collected early or are highly diluted.

Detection is more reliably achieved with spectrophotometric analysis of CSF, typically measuring absorbance around 415 nanometers, which corresponds to bilirubin. This objective testing helps distinguish true xanthochromia from other causes of CSF discoloration. In clinical practice, xanthochromia is used to differentiate SAH from traumatic tap during lumbar puncture, though timing, sample handling, and blood contamination can complicate interpretation.

Clinical significance and management revolve around recognizing prior intrathecal bleeding. If xanthochromia is present or there is sustained suspicion of SAH, imaging with CT or MRI and appropriate neurosurgical evaluation are indicated. Limitations include variability in timing, sample handling, and the potential for false positives or negatives.