A 35-year-old male presents with sudden-onset severe headache ('worst headache of my life'). Non-contrast head CT performed 3 hours after onset is normal. What is the mandatory next diagnostic step?
Answer and explanation
Correct answer: C. Lumbar puncture to assess for cerebrospinal fluid xanthochromia
- Step 1: The clinical presentation is pathognomonic for an acute aneurysmal subarachnoid hemorrhage (SAH).
- Step 2: While non-contrast head CT is highly sensitive in the first 6 hours, a normal CT does not definitively rule out SAH.
- Step 3: A lumbar puncture is mandatory to detect red blood cells and xanthochromia resulting from hemoglobin degradation.
Answer
Lumbar puncture to assess for cerebrospinal fluid xanthochromia.
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