Subarachnoid hemorrhage (summary)

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This is a basic article for medical students and other non-radiologists

Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space. This is usually found centrally (around the circle of Willis) but can occur in other parts of the brain.

Reference article

This is a summary article; read more in our article on subarachnoid hemorrhage.

Summary

  • anatomy
  • epidemiology
    • older middle-age, typically <60 years
    • 3% of strokes and 5% of stroke-deaths
  • presentation
    • headache - described as "thunderclap"
    • neck stiffness (non-specific)
    • acute confusion, neurological signs or reduced conscious level
    • ECG changes (ischemic) or rhythm changes (torsades)
  • pathophysiology
    • 85% rupture of an intracranial aneurysm
    • vascular malformations
    • trauma
  • investigation
    • non-contrast CT head or initial assessment
    • if signs of subarachnoid hemorrhage, CT angiogram
    • lumbar puncture (looking for xanthochromia >12 h after symptoms)
  • treatment
    • depends on the cause but there are general principles
      • high fluid intake (>3500 mL/day) to prevent vasospasm
      • calcium channel blockers (nimodipine) to dilate vessels
      • early neurosurgical discussion
    • aneurysms can be coiled or clipped 

Imaging

  • role of imaging
    • primary diagnosis, e.g. after assessment for acute onset headache
    • determination of cause (e.g. aneurysm), e.g. CT angiography 
    • characterization of aneurysm, e.g. catheter angiography
    • as part of treatment, e.g. interventional coiling
    • follow up
  • radiographic features
    • CT
      • first line investigation (fast, available and cheap)
      • acute blood is hyperdense (bright) on CT
      • blood in the basal cisterns and sulci
      • in the absence of trauma, think of an aneurysm
      • a CT angiogram should identify and characterize any aneurysm
    • MRI
      • helpful to assess underlying brain parenchyma
      • MR angiograms are not as good as CT angiograms
    • DSA
      • this is the gold-standard for assessment of aneurysms
      • it can also be used in treatment (during coiling)