What are the causes of subarachnoid haemorrhage (SAH)?

Aneurysmal SAH (aSAH)
Cause 75%
  • Saccular (berry) aneurysm
    • ACOM (35%)
    • PCOM and ICA (35%)
    • MCA (20%)
    • Bifurcation of the basilar artery (4%)
    • Posterior circulation (8%)
  • Mycotic aneurysm (rare)
Non-aneurysmal SAH
  • Peri mesencephalic haemorrhage (10%)
  • A-V Malformations (<5%)
  • Bleeding diathesis / anticoagulants (<5%)
  • Trauma
  • Angioma
  • Neoplasm
  • Cortical thrombosis
  • Idiopathic / undefines (10%)