Subarachnoid hemorrhage

Background

  • Bleeding into the subarachnoid space (between arachnoid and pia mater)
  • Ruptured cerebral aneurysm accounts for ~85% of nontraumatic SAH
    • Most common locations: anterior communicating artery (30%), posterior communicating artery (25%), MCA bifurcation (20%)
  • Other causes: arteriovenous malformation, perimesencephalic (benign, ~10%), vasculitis, coagulopathy, drug use
  • Mortality: ~50% overall (25% die before reaching hospital, 25% die within 30 days)
  • Risk factors:
    • Hypertension (most important modifiable risk factor)
    • Smoking, heavy alcohol use
    • Family history of SAH or aneurysm (first-degree relative)
    • Polycystic kidney disease, Ehlers-Danlos, connective tissue disorders
    • Prior SAH (risk of rebleeding)
    • Sympathomimetic drug use (cocaine, amphetamines)
  • Peak incidence: age 40-60; female predominance (1.6:1)

Clinical Features

  • "Worst headache of my life" — sudden onset, maximal at onset (thunderclap headache)
  • Sentinel headache: warning leak days-weeks before major rupture (present in ~30-50%)
  • Meningismus (neck stiffness, photophobia) — may take 6-12 hours to develop
  • Loss of consciousness at onset (~50%)
  • Nausea, vomiting (common)
  • Focal neurologic deficits (CN III palsy → posterior communicating artery aneurysm)
  • Seizures (~10% at onset)
  • Terson syndrome: intraocular hemorrhage (subhyaloid/vitreous) associated with severe SAH
  • May present as syncope, cardiac arrest, or altered mental status without headache

Hunt-Hess Grading

  • Grade I: asymptomatic or mild headache
  • Grade II: moderate-severe headache, nuchal rigidity, CN palsy
  • Grade III: drowsiness, confusion, mild focal deficit
  • Grade IV: stupor, moderate-severe hemiparesis
  • Grade V: coma, decerebrate posturing

Differential Diagnosis

Headache

Common

Killers

Maimers

Others

Aseptic Meningitis

Evaluation

Non-Contrast CT Head

  • First-line test
  • Sensitivity ~98% within 6 hours of onset, ~93% at 12 hours, decreasing to ~50% by day 5-7[1]
  • Fisher grade: amount of blood predicts vasospasm risk
  • Modern thin-cut CT with experienced radiologist within 6 hours may approach 100% sensitivity

Lumbar Puncture

  • Required if CT negative and clinical suspicion remains
  • Classic finding: xanthochromia (yellow discoloration from bilirubin in CSF)
    • Takes 6-12 hours to develop — LP performed <6 hours after onset may miss xanthochromia
  • Elevated RBCs that do NOT clear across sequential tubes (vs traumatic tap which clears)
  • Elevated opening pressure
  • Traumatic tap vs SAH: controversial; visual xanthochromia and clinical context are most important

Ottawa SAH Rule

  • For alert patients >15 years with new severe nontraumatic headache reaching maximum intensity within 1 hour
  • 100% sensitivity (validation study) — if none present, SAH effectively ruled out[2]:
    • Age ≥40
    • Neck pain or stiffness
    • Witnessed loss of consciousness
    • Onset during exertion
    • Thunderclap headache (instant peak)
    • Limited neck flexion on exam

CT Angiography (CTA)

  • Obtain with initial CT if SAH confirmed or high suspicion
  • Identifies aneurysm location and morphology for surgical/endovascular planning
  • Sensitivity >95% for aneurysms >3 mm

Labs

  • CBC, BMP, coagulation studies (PT/INR, PTT)
  • Type and screen
  • Troponin (neurogenic myocardial stunning)
  • Finger stick glucose

Management

ED Management

  • ABCs, IV access, continuous monitoring
  • Blood pressure control:
    • Target SBP <160 mmHg until aneurysm secured (reduce rebleeding risk)
    • Nicardipine infusion (5-15 mg/hr, titrate q5min) — preferred
    • Labetalol 10-20 mg IV q10-20min
    • Avoid nitroprusside (increases ICP)
  • Seizure management: benzodiazepines acutely; prophylactic AEDs controversial
  • Treat headache: acetaminophen; short-acting opioids cautiously
    • Avoid ketorolac (platelet inhibition)
  • Aminocaproic acid (tranexamic acid): may reduce rebleeding risk before aneurysm secured — 4g IV loading dose (discuss with neurosurgery)
  • Reverse anticoagulation if applicable

Definitive Treatment

  • Neurosurgery/neurointerventional consultation emergently
  • Aneurysm securing (within 24 hours ideally):
    • Endovascular coiling (preferred for most aneurysms) OR
    • Surgical clipping
  • ICU admission

Complications (Post-Hemorrhage)

  • Rebleeding: highest risk in first 24 hours (~4%); most devastating complication
  • Vasospasm: occurs days 3-14 (peak day 7); monitor with daily TCDs
    • Treat with nimodipine 60 mg PO/NG q4h x 21 days (improves outcomes; does not prevent vasospasm)
    • Triple-H therapy (hypertension, hypervolemia, hemodilution) — only after aneurysm secured
  • Hydrocephalus: acute (requires EVD) or chronic (VP shunt)
  • Hyponatremia: cerebral salt wasting vs SIADH
  • Neurogenic cardiac dysfunction: Takotsubo-like, neurogenic pulmonary edema

Disposition

  • All confirmed SAH: emergent neurosurgical consultation and ICU admission
  • Transfer to neurosurgical center if local capabilities unavailable
  • SAH ruled out (negative CT + negative LP): may discharge with headache precautions and PCP follow-up

Calculators

Template:Ottawa SAH Calculator

Modified Fisher Scale

Modified Fisher Scale — SAH Vasospasm Risk
CT Findings Select Grade
Grade

1 Grade 0 — No SAH or IVH (0)

Grade 1 — Thin SAH, no IVH (1)

Grade 2 — Thin SAH with IVH (2)

Grade 3 — Thick SAH, no IVH (3)

Grade 4 — Thick SAH with IVH (4)

Modified Fisher Grade
Interpretation — Risk of Symptomatic Vasospasm
Grade Vasospasm Risk Description
0 | ~0% | No subarachnoid blood detected.
1 | ~24% | Focal or diffuse thin SAH, no intraventricular hemorrhage (IVH).
2 | ~33% | Focal or diffuse thin SAH with IVH.
3 | ~33% | Focal or diffuse thick SAH (>1mm), no IVH.
4 | ~40% | Focal or diffuse thick SAH with IVH. Highest vasospasm risk.
References
  • Fisher CM, Kistler JP, Davis JM. Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning. Neurosurgery. 1980;6(1):1-9. PMID 7354892.
  • Frontera JA, Claassen J, Schmidt JM, et al. Prediction of symptomatic vasospasm after subarachnoid hemorrhage: the modified Fisher scale. Neurosurgery. 2006;59(1):21-27. PMID 16823296.

See Also

References

  1. ↑ Perry JJ, et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage. BMJ. 2011;343:d4277. PMID 21768192
  2. ↑ Perry JJ, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013;310(12):1248-1255. PMID 24065011
  • Connolly ES Jr, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline from the AHA/ASA. Stroke. 2012;43(6):1711-1737. PMID 22556195
  • Edlow JA, et al. Diagnosis of subarachnoid hemorrhage. Stroke. 2023;54(4):1058-1072. PMID 36848423
  • van Gijn J, et al. Subarachnoid haemorrhage. Lancet. 2007;369(9558):306-318. PMID 17258671
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