• Clinical science

Subarachnoid hemorrhage


Subarachnoid hemorrhage (SAH) refers to bleeding into the subarachnoid space. SAH most often results from head trauma, while nontraumatic SAH is most commonly due to the rupture of an aneurysm involving the circle of Willis. SAH typically presents with severe headache, nausea/vomiting, and/or acute loss of consciousness. A fresh intracranial hemorrhage appears hyperdense on a non-contrast CT scan, confirming diagnosis. CT angiography and lumbar puncture may be necessary for further evaluation. Treatment consists of carefully lowering blood pressure and measures to prevent cerebral vasospasm. Clipping or coiling of the bleeding aneurysm may be necessary to prevent potentially fatal rebleeding. SAH is associated with a high mortality as a result of frequent complications such as rebleeding and secondary ischemic strokes due to vasospasm.


  • Traumatic: head trauma is the most common cause of SAH
  • Nontraumatic
    • Peak incidence: around the age of 50
    • > (3:2)
    • Responsible for 5% of all cases of stroke


Epidemiological data refers to the US, unless otherwise specified.


  • TraumaticTraumatic brain injury
  • Nontraumatic/spontaneous
    • Ruptured aneurysm usually in the circle of Willis
      • Berry aneurysm: (80% of cases of nontraumatic SAH)
        • Highest risk of rupture
        • Round, saccular aneurysms located at major branches of large arteries
        • Multifactorial etiology
    • Ruptured arteriovenous malformation (AVM) (10% of cases of nontraumatic SAH)
    • Others: cortical thrombosis, angioma, neoplasm, infection
  • Triggers: most cases unknown, may be triggered by an acute rise in blood pressure (e.g., caffeine consumption, acute anger, physical exertion)
  • Risk factors




Clinical features



  • Nonenhanced CT (best initial test ): shows blood in subarachnoid space
  • Lumbar puncture (LP), if CT negative
    • ↑↑ RBCs , WBCs , ↑ protein (gamma globulin)
    • Glucose normal
    • ↑ or ↔︎ opening pressure
    • Yellowish (xanthochromia) or red discoloration
  • Angiography
    • Digital subtraction angiography (DSA): determines the site of bleeding/aneurysm preoperatively
    • CT angiography (CTA); : if CT does not confirm SAH in clinically suspected or high-risk cases (emergent or unstable patients)



Initial treatment

  • Control blood glucose levels

Definitive treatment

  • Surgical clipping (treatment of choice) and/or endovascular coiling (increasingly used alternative for poor surgical candidates) should be performed early to prevent rebleeding
  • If hydrocephalus is present → ventricular drain, serial LPs, or permanent ventriculoperitoneal shunt

Use of nitrates should be avoided since they may raise ICP!



  • Vasospasm (∼ 30% of cases, often in those with ruptured aneurysms): usually occurs between the 3rd and the 8th day after SAH
    • ⅓ of patients suffer ischemic strokes due to vasospasm
    • Transcranial doppler study should be performed daily to assess the severity of vasospasms.
  • Rebleeding (∼ 20% of cases): most often within the first two weeks
    • The risk of rebleeding is highest during the first 24 hours after SAH.
  • Hydrocephalus (∼ 15% of cases)
  • Seizures
  • Cardiac dysfunction


We list the most important complications. The selection is not exhaustive.


  • 50% mortality rate within the first 30 days
  • Survivors: increased rates of neurologic impairment (e.g., cognitive, mood changes, functional, epilepsy) and increased risk of recurrent SAH