A 60-year-old hypertensive man presents with sudden onset severe headache ('thunderclap headache'), neck stiffness, and a normal CT head. Lumbar puncture at 12 hours shows xanthochromia. What does xanthochromia specifically indicate?

• A Traumatic tap from the lumbar puncture needle
• B Bacterial meningitis with high protein content
• C Viral encephalitis with blood-brain barrier disruption
• D Subarachnoid haemorrhage (SAH) — degradation of haemoglobin to bilirubin in CSF ✓

Explanation

Xanthochromia is the yellow discolouration of CSF caused by oxyhaemoglobin and bilirubin released from lysed red blood cells following subarachnoid haemorrhage. It develops within 2-4 hours of SAH and persists for up to 2 weeks, distinguishing SAH from a traumatic LP (where xanthochromia is absent and the supernatant remains clear). Spectrophotometric analysis of CSF for oxyhaemoglobin and bilirubin is the gold standard investigation when CT head is negative and SAH is suspected.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.