subarachnoid hemorrhage (SAH)

Introduction

hemorrhage into the subarachnoid space underneath the subarachnoid membrane that results in pressure on the brain or bleeding into the brain.

Etiology

• arteriovenous malformation
  • ruptured congenital ('berry') aneurysm (80%)
• intracranial carotid artery dissection
• hypertension is risk factor
• drug abuse
  • intravenous drug abuse
  • cocaine abuse
• tobacco abuse
• polycystic kidney disease
• amyloid angiopathy, not listed as risk in
• inflammation, not listed as risk in
• infection, not listed as risk in

Epidemiology

• accounts for 10% of all strokes
• age > 40-45 (risk factor)

Pathology

• hemorrhage into the subarachnoid space results in pressure on the brain or bleeding into the brain

Clinical manifestations

• sudden onset of severe 'thunderclap' headache
  • many patients do not present with classic 'thunderclap' headache
  • because headache is so common, diagnosis is often missed
  • sentinal hemorrhage (severe headache during previous 2-3 weeks)
• obtundation occurs often
• loss of consciousness
• vomiting
• neck pain or stiffness
• hypertension: BP ? 160/100 mm Hg
• focal neurologic signs may occur
• subhyaloid hemorrhage on funduscopy
• grading with Hunt-Hess clinical grading scale
• Ottawa SAH rule sensitivity 100% with specificity 14%

Laboratory

• serum magnesium
  • maintain 2.0-2.5 mmol/L (4.8-6.0 mg/dL) if infusing magnesium sulfate

Diagnostic procedures

• lumbar puncture (LP) with CSF examination for blood &/or CSF bilirubin if non contrast CT is negative & index of suspicion is high
  • if > 6 hours has elapsed
  • neither history & physical examination nor CT can rule out subarachnoid hemorrhage
• arteriography for confirmation of diagnosis & opportunity for surgical repair

Radiology

• computed tomography (CT) without contrast
  • blood is subarachnoid space reveals hemorrhage
  • sensitivity is 99.5%
  • sensitivity 100% within 6 hours
    • may be used without LP if within 6 hours
• magnetic resonance imaging is alternative
• CT angiography
  • delineates anatomy of ruptured cerebral aneurysm
  • rules out other causes of subarachnoid hemorrhage
    • intracranial arterial dissection
    • mycotic aneurysm
  • identification of cerebral vasospasm as a complication

Complications

• rebleeding within 48 hours
• ischemia from cerebral vasospasm induced by presence of extravasated blood
  • occurs 5-10 days after subarachnoid hemorrhage
• hydrocephalus associated with intracranial hypertension & high mortality
  • neurosurgical plaacement of external ventricular drain
• increased intracranial pressure
• hyponatremia is common
• seizures early after stroke
  • more common with hemorrhagic stroke than ischemic stroke (15% vs 4%)
  • more common with cortical stroke than subcortical stroke (19% vs 10%)
  • do not predict mortality or function at 6 months
• rebleeding of intracranial aneurysm is the major cause of morbidity

Differential diagnosis

• carotid artery dissection, vertebral artery dissection
• venous sinus thrombosis
• pituitary apoplexy
• reversible cerebral vasoconstriction syndrome
• intracranial hemorrhage

Management

• see general measures under stroke (CVA)
• surgical clipping of ruptured intracranial aneurysm with 24-72 hours
  • endovascular coiling with better outcomes than neurosurgical clipping see ISAT
• craniotomy for intracranial aneurysm
• blood pressure control
  • target blood pressure < 140/80 to prevent rebleeding
  • nicardipine & labetolol preferred agents
• vasospasm may begin on day 5
  • nimodipine for vasospasm
    • 60 mg PO every 4 hours for 3 weeks
    • start therapy 96 hours after subarachnoid hemorrhage
  • hypervolemia for symptomatic vasospasm
  • hypertension if aneurysm has been surgically repaired
  • angioplasty
  • intra-arterial papaverine
  • intravenous magnesium sulfate may be of benefit
    • IV bolus of 16 mmol (1920 mg) over 30 minutes followed by
    • continuous infusion of 8 mmol (960 mg) per hour for 10 days or until vasospasm stops
    • monitor serum magnesium (see Laboratory)
• control bleeding
  • maintain platelet count of >= 100,000/uL
• seizure prophylaxis
• prognosis
  • better for those who present with normal mental status
  • initial misdiagnosis compromises clinical outcome
• prevention:
  • incidental cerebral aneurysms < 10 mm are followed by MRI
  • surgery for cerebral aneurysms > 10 mm
  • smoking cessation
  • blood pressure control
• neurorehabilitation

More general terms

• cerebrovascular hemorrhage

More specific terms

• Terson syndrome

Additional terms

• hemorrhagic stroke
• increased intracranial pressure (ICP)
• subarachnoid space