Aneurysmal subarachnoid hemorrhage is a neurosurgical emergency caused by rupture of an intracranial aneurysm (85% of spontaneous SAH), with a mortality rate of ~50% and mean age of onset in the mid-fifties. [1-2] Approximately 25% of patients die before hospital admission. [1] Prompt recognition and treatment are essential to prevent rebleeding and secondary brain injury.
1. History
- Hallmark symptom: Sudden, severe "thunderclap" headache reaching maximum intensity within <1 minute, often described as the "worst headache of my life" [1][3]
- Sudden onset is more diagnostically important than severity alone [3]
- Headache is the only symptom in ~50% of cases [1]
- Ask about onset during exertion (Valsalva, coitus, heavy lifting) [2]
- Sentinel headache: 10–43% of patients report a less severe warning headache days to weeks before the major bleed [2][4]
- Associated symptoms: nausea/vomiting, photophobia, neck pain/stiffness, transient loss of consciousness, seizure [1-2]
- The classic thunderclap headache is absent in ~25% of patients — maintain high suspicion for any new or worsening headache [2]
- Important negatives: no trauma, no history of recurrent headaches, no prior aneurysm/SAH
2. Alarm Features
- Thunderclap headache (instantly peaking) [5]
- Witnessed loss of consciousness (26–53% of aSAH) [1]
- Seizure at headache onset [2]
- Acute focal neurologic deficits (CN III palsy with PComm aneurysm, hemiparesis) [1]
- Meningismus / nuchal rigidity
- Sudden buckling of the legs [2]
- Coma or rapidly declining GCS
- Signs of elevated ICP: papilledema, Cushing reflex (hypertension, bradycardia, irregular respirations)
- Terson syndrome (intraocular hemorrhage) — occurs in up to 46%, associated with poor prognosis [2]
3. Medications
- Relevant contributors/risk factors:
- Anticoagulants (warfarin, DOACs) — immediate reversal is strongly recommended per AHA/ASA 2023 guidelines [4]
- Sympathomimetics (cocaine, amphetamines) — can precipitate aneurysm rupture
- NSAIDs/antiplatelet agents — may worsen bleeding
- Key treatments:
- Nimodipine 60 mg PO q4h × 21 days — the only pharmacological agent proven to reduce delayed cerebral ischemia (DCI) and improve outcomes [3][6]
- Antihypertensives (nicardipine, labetalol, clevidipine) to maintain SBP ≤160 mmHg pre-aneurysm repair [4][7]
- Short-term anticonvulsants (levetiracetam preferred) — prophylaxis considered for high-grade SAH [7]
- Contraindicated/avoid:
- Tranexamic acid — does not reduce rebleeding or improve functional outcomes [7]
- Statins and magnesium sulfate — not beneficial for vasospasm prevention per AHA/ASA 2023 [7]
- Avoid antihypertensives post-aneurysm repair unless BP is substantially elevated [3]
- Avoid hypotension (MAP <65 mmHg) [4]
4. Diet
- NPO initially if neurosurgical intervention anticipated
- Maintain euvolemia — avoid both hypovolemia (increases DCI risk) and hypervolemia (increases complications without benefit) [7]
- Early enteral nutrition when feasible to reduce pulmonary complications [7]
- Long-term: smoking cessation, alcohol moderation, and blood pressure management through dietary modifications (DASH diet)
5. Review of Systems
- Neuro: headache quality/onset, vision changes (diplopia from CN III palsy), weakness, speech difficulty, seizure, LOC
- Cardiac: chest pain, palpitations (neurogenic cardiac injury/Takotsubo)
- Pulmonary: dyspnea (neurogenic pulmonary edema in ~4%) [7]
- GI: nausea, vomiting (common with elevated ICP)
- Constitutional: recent fevers (to differentiate from meningitis)
- Psych: confusion, agitation
6. Collateral History and Family History
- Family history of intracranial aneurysm or SAH — screening recommended for patients with ≥1 first-degree relative with aneurysm/SAH [2]
- History of autosomal dominant polycystic kidney disease (ADPKD) — associated with increased aneurysm prevalence
- Connective tissue disorders: Ehlers-Danlos type IV, Marfan syndrome, fibromuscular dysplasia
- Collateral from witnesses: exact time of headache onset, LOC, seizure activity, preceding exertion
- Medication list: anticoagulants, antiplatelets, stimulant use
7. Risk Factors
- Hypertension (most important modifiable risk factor) [8-9]
- Smoking (strongest modifiable risk factor for aneurysm rupture) [8-9]
- Excessive alcohol consumption [9]
- Female sex (higher incidence, especially postmenopausal)
- Age (peak incidence 40–60 years)
- Family history of SAH or intracranial aneurysm
- Large aneurysm size (>7 mm, especially posterior circulation) [8]
- Cocaine/sympathomimetic use
- Prior SAH (risk of new aneurysm formation)
- Prevalence of intracranial aneurysms: 2–6% of the global population; only 0.25% rupture annually [2]
8. Differential Diagnosis
- Reversible cerebral vasoconstriction syndrome (RCVS) — recurrent thunderclap headaches, often triggered by vasoactive substances; may have cortical SAH [1]
- Cerebral venous sinus thrombosis — headache, focal deficits, seizures; diagnosed by CT/MR venography [1]
- Intracerebral hemorrhage (hypertensive, AVM)
- Meningitis/encephalitis — fever, meningismus, CSF pleocytosis
- Cervical artery dissection — neck pain, Horner syndrome, focal deficits
- Migraine — most common misdiagnosis of SAH [3]
- Tension headache — second most common misdiagnosis [3]
- Pituitary apoplexy — sudden headache, visual field deficits, hormonal crisis
- Hypertensive emergency
- Pseudo-SAH — CT appearance following cardiac arrest; distinct from true SAH [1]
- Perimesencephalic SAH (nonaneurysmal) — blood confined to perimesencephalic cisterns, excellent prognosis, ~10% of spontaneous SAH [9]
9. Past Medical History
- Prior SAH or known intracranial aneurysm
- Hypertension, especially poorly controlled
- ADPKD, connective tissue disorders
- Coagulopathy or anticoagulant use
- Prior neurosurgical procedures
- Substance use history (cocaine, tobacco, alcohol)
- History of recurrent headaches (helps differentiate from new-onset headache)
10. Physical Exam
- Vital signs: Hypertension (often severe), tachycardia; watch for Cushing triad (hypertension, bradycardia, irregular respirations)
- Neurologic exam:
- GCS — document on arrival; grade using Hunt & Hess or WFNS scale [1-2]
- Meningismus — nuchal rigidity, Kernig and Brudzinski signs
- CN III palsy — ptosis, "down and out" eye, fixed dilated pupil (PComm aneurysm) [1]
- CN VI palsy — from elevated ICP
- Focal motor deficits, aphasia
- Limited neck flexion (Ottawa SAH Rule criterion) [10]
- Fundoscopy: Subhyaloid/preretinal hemorrhages (Terson syndrome) [2]
- Skin: Petechiae or ecchymoses (coagulopathy)
11. Lab Studies
- CBC with differential, BMP (electrolytes — watch for hyponatremia), coagulation studies (PT/INR, PTT)
- Troponin — neurogenic myocardial injury occurs frequently; elevated troponin associated with worse outcomes [11]
- Type and screen (anticipate surgical intervention)
- BNP/NT-proBNP — if cardiac dysfunction suspected
- Glucose — hyperglycemia within 72 hours increases DCI and death [7]
- Magnesium — hypomagnesemia common and should be corrected [3]
- CSF analysis (if LP performed): RBC count (non-clearing across tubes), xanthochromia (spectrophotometry preferred), opening pressure [2][12]
- Xanthochromia takes 6–12 hours to develop; present in 90% by 12 hours [12]
- RBC <2,000/µL with no xanthochromia effectively rules out SAH [12]
12. Imaging
- First-line: Noncontrast CT head [1][3-4]
- Sensitivity within 6 hours: ~98.7–100% [1][3-4]
- Sensitivity declines to ~50% by day 5–7 [3][13]
- Look for hyperdense blood in basal cisterns, Sylvian fissures, interhemispheric fissure
- Grade with Modified Fisher Scale (predicts vasospasm risk) [2][8]
- If CT negative and clinical suspicion remains:
- >6 hours from onset: LP for xanthochromia (AHA/ASA 2023 strong recommendation for CT-LP approach) [4]
- CTA — ACEP 2019 allows either CT-LP or CT-CTA approach (weak recommendation); AHA/ASA 2023 favors CT-LP [4][14]
- MRI with FLAIR — alternative to LP, especially if presenting days later; limited in perimesencephalic region [2][13]
- Once SAH confirmed:
- CTA — detects aneurysms ≥2 mm; often obtained simultaneously with initial CT [13]
- Digital subtraction angiography (DSA) — gold standard for aneurysm detection and treatment planning [13]
- If no aneurysm found (~15% of cases), repeat DSA in 7–10 days [2]
The following figure outlines the diagnostic algorithm for SAH evaluation:
13. Special Tests
- Ottawa SAH Rule — validated clinical decision tool for alert patients >15 years with new severe nontraumatic headache peaking within 1 hour: [10]
- Investigate if ≥1 present: age ≥40, neck pain/stiffness, witnessed LOC, onset during exertion, thunderclap headache, limited neck flexion
- Sensitivity: 99–100%; specificity: ~15–23% [2][10][15]
- Not applicable if: new neurologic deficits, prior aneurysm/SAH/tumor, recurrent headache history
- Hunt & Hess Scale and WFNS Scale — clinical grading for severity and prognosis [2][17]
- Modified Fisher Scale — radiographic grading for vasospasm risk [2]
- Transcranial Doppler (TCD) — screens for middle cerebral artery vasospasm (90% sensitivity, 92% NPV); used during ICU monitoring [7]
- CT perfusion — predicts DCI when performed ~3 days post-SAH [7]
- Continuous EEG — monitors for nonconvulsive seizures and DCI (alarms in 96% of DCI patients) [7]
14. ECG
ECG abnormalities occur in up to 75–90% of SAH patients and are caused by catecholamine surge and autonomic dysfunction: [11][18]
- Most common findings:
- QT prolongation (most prevalent, ~42% on admission) [19]
- Deep, symmetric T-wave inversions ("cerebral T waves") — diffuse, wide, and symmetric [18][20]
- ST-segment changes (elevation or depression) [11]
- Pathological Q waves [20]
- Arrhythmias:
- Sinus tachycardia (most common arrhythmia) [18]
- Atrial fibrillation [18]
- Ventricular tachycardia, torsades de pointes, VF (especially with prolonged QT and hypokalemia) [18]
- Clinical significance:
- ECG abnormalities are independent predictors of mortality [20]
- QT prolongation and tachycardia predict angiographic vasospasm [19]
- Can mimic acute coronary syndrome — differentiate from primary cardiac ischemia [18]
- Consider Takotsubo cardiomyopathy / stunned myocardium [18]
- Obtain ECG on admission; if abnormal, pursue troponin and echocardiography [3]
15. Assessment
- SAH is the third most common stroke subtype, with an incidence of ~7.9 per 100,000 person-years [1][8]
- Severity stratification using Hunt & Hess or WFNS scale is essential for prognosis and treatment decisions: [2][4]
- Grades 1–3: "good grade" — generally favorable outcomes with treatment
- Grades 4–5: "high grade" — 40% achieve favorable outcome with treatment [4][7]
- Misdiagnosis rate remains high, especially in neurologically intact patients presenting with headache alone — most commonly misdiagnosed as migraine or tension headache [2-3]
- Key complications to anticipate:
- Rebleeding — highest risk in first 24 hours; most devastating complication
- Delayed cerebral ischemia (DCI) — affects ~30%, occurs days 4–14 [7]
- Hydrocephalus — up to 87% [7]
- Seizures — up to 15% [7]
- Hyponatremia (cerebral salt wasting) [7]
- Neurogenic cardiac injury / Takotsubo cardiomyopathy [1]
- Neurogenic pulmonary edema (~4%) [7]
16. Treatment Plan
Initial Stabilization (ED):
- ABCs — intubate if GCS ≤8 or inability to protect airway
- BP control: SBP ≤160 mmHg (nicardipine drip preferred); avoid hypotension (MAP <65) [4][7]
- Reverse anticoagulation immediately if applicable [4]
- Elevate head of bed 30°
- Analgesics for headache (avoid NSAIDs; use acetaminophen, short-acting opioids)
- Antiemetics (ondansetron)
- Seizure treatment if active (benzodiazepines → levetiracetam)
Definitive Treatment:
- Aneurysm repair within 24 hours is recommended: [7]
- Endovascular coiling — may have better 1-year functional outcomes vs. clipping [7]
- Surgical clipping — via craniotomy; preferred in certain aneurysm locations/morphologies
- Complete obliteration reduces rebleeding risk; if partial, retreatment in 1–3 months [7]
- Nimodipine 60 mg PO q4h × 21 days — start within 96 hours [3][6]
- Maintain euvolemia with isotonic fluids [3][7]
- Fludrocortisone for hyponatremia [7]
- EVD placement for acute symptomatic hydrocephalus
- VTE prophylaxis (mechanical initially; pharmacologic after aneurysm secured) [3]
- Treat fever aggressively; maintain normothermia [3]
- Glucose management — avoid hyperglycemia [7]
17. Disposition
- All confirmed SAH patients require admission to a neurosurgical ICU, ideally at a high-volume center (>35 cases/year) [3][7]
- Transfer to a comprehensive stroke center or facility with neurosurgical and neurointerventional capabilities if not available locally [2]
- Observation indications: Patients with equivocal LP results or incidental unruptured aneurysms found on CTA may require neurosurgical consultation and close follow-up
- Treatment is not recommended for patients with partial loss of brainstem reflexes, lack of purposeful response to noxious stimuli, or imaging showing large completed ischemic infarct or global cerebral edema of anoxic brain injury [7]
- Discharge criteria (post-treatment, typically after 14–21 day ICU stay): neurologically stable, past the DCI risk window, tolerating oral nimodipine, no active hydrocephalus
18. Follow Up / Return Precautions
- Follow-up imaging: Repeat vascular imaging (CTA or DSA) to assess aneurysm obliteration; retreatment if incomplete [7]
- If no aneurysm found initially, repeat DSA in 7–10 days [2]
- Long-term follow-up:
- Neurosurgery follow-up for aneurysm surveillance
- Screen first-degree family members for aneurysms if familial history [2]
- Physical, occupational, cognitive, and neuropsychological rehabilitation [3]
- Screen for and treat depression, anxiety, and PTSD — common long-term sequelae [1][3]
- Return precautions (for patients discharged after negative workup):
- Modifiable risk factor management: smoking cessation, blood pressure control, alcohol moderation [9]
- Expected recovery: Survivors face elevated risk of long-term neuropsychiatric sequelae; mean age of onset in mid-fifties leads to many years of reduced quality of life [1]
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