What is the recommended emergency evaluation and management for a patient with suspected acute subarachnoid hemorrhage?

Emergency Evaluation and Management of Acute Subarachnoid Hemorrhage

Immediate Diagnostic Approach

Obtain a non-contrast head CT immediately upon arrival—this is the cornerstone of SAH diagnosis and must be performed without delay. 1, 2

CT Imaging Protocol

• Non-contrast CT head is mandatory as the first test—never use contrast for initial SAH evaluation, as the goal is to detect blood, not characterize vessels 2
• Timing is critical for interpretation: CT sensitivity is 98-100% when performed within 6 hours of symptom onset, declining to 93% at 24 hours and 57-85% by day 6 1, 2
• The scan must extend from below the foramen magnum to above the circle of Willis and middle cerebral artery bifurcation 1

When to Perform Lumbar Puncture

If CT is performed within 6 hours of headache onset AND is read as normal by a neuroradiologist using third-generation or higher CT scanner, lumbar puncture is NOT required 1, 2, 3

Lumbar puncture is mandatory if:

• CT performed >6 hours after symptom onset 1, 2
• High clinical suspicion persists despite negative CT 1
• No experienced neuroradiologist available to interpret the scan 1
• Lower generation CT scanner used 1
• Patient in altered state of consciousness 1

LP timing and technique:

• Perform >6 hours from most recent symptom onset to allow xanthochromia development 4
• Send CSF for: cell count with differential, xanthochromia (spectrophotometry—sensitivity 100%, specificity 95.2%), protein, glucose 4
• Proper specimen handling is critical—xanthochromia must be analyzed by spectrophotometry, not visual inspection alone 1

Clinical Recognition

Maintain extremely high suspicion for SAH in patients with acute onset severe headache—this is frequently misdiagnosed (12% misdiagnosis rate), and missing it increases mortality 4-fold 1

Classic Presentation Features

• Thunderclap headache: sudden onset reaching maximum intensity within 1 hour, often described as "worst headache of my life" 1, 2
• Neck pain or stiffness (meningismus present in 35% of cases) 1
• Nausea and vomiting 1
• Loss of consciousness (occurs in significant proportion) 1
• Seizures (up to 20% of patients, most commonly in first 24 hours) 1

Warning Leak Recognition

19.4% of patients report sentinel headache 2-8 weeks before major rupture—recognizing this can be lifesaving 1

• Sentinel bleeds cause milder headache lasting hours to days 1
• Meningismus uncommon with warning leaks 1
• Any sudden severe headache warrants investigation even if symptoms subsequently improve 1

Vascular Imaging After Positive CT

Once SAH is confirmed on CT, proceed immediately to aneurysm identification—early rebleeding occurs in 4-13.6% within first 24 hours, with one-third of rebleeds occurring within 3 hours 1

Imaging Hierarchy

• CT angiography (CTA) is the appropriate next step: fast, non-invasive, >90% sensitivity for aneurysms 2
• CTA limitations: sensitivity decreases to 61-85% for aneurysms <3mm 2, 5
• Digital subtraction angiography (DSA) with 3D rotational angiography remains gold standard: >98% sensitivity and specificity, mandatory for treatment planning 1, 2
• DSA is indicated except when aneurysm was previously diagnosed by noninvasive angiogram 1

Initial Management Priorities

Patients with aneurysmal SAH must be treated as a medical emergency with immediate evaluation by physicians with stroke expertise 1

Critical Early Actions

• Urgent neurosurgical consultation without delay—high early rebleeding risk mandates immediate assessment 1
• Transfer to centers with neurosurgical expertise treating aneurysms regularly using both endovascular and surgical techniques 1
• Low-volume hospitals (<10 SAH cases/year) should transfer patients early to high-volume centers (>35 cases/year) with multidisciplinary neuro-intensive care 1

Blood Pressure Management

• Between symptom onset and aneurysm obliteration, control blood pressure with titratable agent—balance rebleeding risk against maintaining cerebral perfusion pressure 1
• Avoid rapid intracranial pressure reduction, which increases rebleeding likelihood 6

Definitive Treatment Timing

• Surgical clipping or endovascular coiling should be performed as early as feasible to reduce rebleeding rate 1
• For aneurysms amenable to both techniques, endovascular coiling should be considered 1
• Complete obliteration of the aneurysm is recommended whenever possible 1

Common Pitfalls to Avoid

Never obtain contrast-enhanced CT as initial test—this obscures blood detection 2

Never skip lumbar puncture if CT performed >6 hours after onset, even if CT appears normal—sensitivity drops significantly after this window 1, 2

Never dismiss headache as benign based solely on normal CT if clinical suspicion is high—1.4% of SAH patients are diagnosed only after vascular imaging despite normal CT and CSF 1

Never delay neurosurgical consultation—rebleeding peaks in first 2-12 hours with catastrophic outcomes 1

Never use MRI as first-line test in acute setting—practical limitations include availability, difficulty scanning acutely ill patients, motion artifact, longer study time, and cost 1