A 70-year-old hypertensive man presents with sudden onset severe headache described as 'the worst headache of his life.' CT brain performed 2 hours after onset is reported as normal. Lumbar puncture shows xanthochromia. What is the gold-standard next investigation to identify an underlying vascular cause?
- A CT angiography of the circle of Willis
- B MR angiography with gadolinium
- C Digital subtraction angiography (DSA) ✓
- D Transcranial Doppler ultrasonography
Explanation
Digital subtraction angiography (DSA) remains the gold standard for detecting intracranial aneurysms causing subarachnoid haemorrhage, offering superior spatial resolution and the ability to characterise aneurysm morphology, neck anatomy, and flow dynamics, which is essential for treatment planning (clipping versus coiling). CT angiography has high sensitivity for aneurysms over 3 mm and is widely used as the first-line vascular investigation given its speed and availability, but DSA retains gold-standard status and is required when CTA is negative or inconclusive. MRA is useful but has lower sensitivity for small aneurysms.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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