A 58-year-old man with hypertension presents to the emergency department with sudden-onset severe headache, neck stiffness, and photophobia. Non-contrast CT head shows hyperdensity in the basal cisterns and sulci. What is the most appropriate next step in management?

## Clinical Context The patient presents with the classic triad of subarachnoid hemorrhage (SAH): sudden severe headache, neck stiffness, and photophobia. Non-contrast CT demonstrates hyperdensity in the basal cisterns and sulci, confirming acute SAH. ## Diagnostic Algorithm for SAH **Key Point:** Once SAH is confirmed on non-contrast CT, the immediate priority is to identify the source of bleeding—most commonly a ruptured cerebral aneurysm (80–85% of non-traumatic SAH). **High-Yield:** CTA (CT angiography) is the gold standard next step after CT-confirmed SAH because it: - Rapidly identifies aneurysms with >95% sensitivity - Detects other vascular lesions (AVM, dissection) - Is faster and more readily available than conventional angiography - Guides urgent neurosurgical/neurointerventional planning ## Why CTA is Superior to Alternatives | Step | Timing | Indication | Limitation | |------|--------|-----------|------------| | **CTA** | Immediate (within 1 hour) | First-line after CT-confirmed SAH | May miss small aneurysms (<3 mm); requires IV contrast | | **Lumbar puncture** | After imaging rules out mass effect | Only if CT is negative but SAH suspected clinically | Contraindicated if mass effect present; delays definitive diagnosis | | **Conventional angiography** | Delayed (after CTA) | Gold standard for aneurysm confirmation and treatment planning | Invasive; reserved for therapeutic intervention | | **MRI** | Delayed | Not first-line for acute SAH | Slower; less sensitive for acute blood; not practical in acute setting | **Clinical Pearl:** Lumbar puncture is NOT the next step in a patient with CT-confirmed SAH; it carries risk of herniation if there is mass effect and delays definitive vascular imaging. ## Management Sequence ```mermaid flowchart TD A["Sudden severe headache + meningeal signs"]:::outcome --> B["Non-contrast CT head"]:::action B --> C{"SAH on CT?"}:::decision C -->|"Yes (hyperdensity in cisterns)"|D["STAT CTA head/neck"]:::action C -->|"No, but high clinical suspicion"|E["Lumbar puncture for xanthochromia"]:::action D --> F{"Aneurysm found?"}:::decision F -->|"Yes"|G["Neurosurgery/Neurointerventional consult"]:::action F -->|"No"|H["Conventional angiography or repeat CTA"]:::action E --> I{"Xanthochromia present?"}:::decision I -->|"Yes"|J["Proceed to CTA"]:::action ``` **Key Point:** The sequence is: clinical suspicion → non-contrast CT → (if positive) CTA → aneurysm management. Lumbar puncture is reserved for cases where CT is negative but clinical suspicion remains high.