Subarachnoid haemorrhage is seen as hyperdense material in the subarachnoid space

The most common cause of SAH is head injury and this is called traumatic SAH. In the absence of trauma, SAH is termed spontaneous SAH. The rest of this note focuses on spontaneous SAH.

Causes of spontaneous SAH include:

• Intracranial aneurysm* (saccular ‘berry’ aneurysms): this accounts for around 85% of cases. Conditions associated with berry aneurysms include adult polycystic kidney disease, Ehlers-Danlos syndrome and coarctation of the aorta
• Arteriovenous malformation
• Pituitary apoplexy
• Arterial dissection
• Mycotic (infective) aneurysms
• Perimesencephalic (an idiopathic venous bleed)
• Sickle cell disease

PC

• Headache: typically sudden-onset (‘thunderclap’ or ‘baseball bat’), severe (‘worst of my life’) and occipital
  • May have a preceding sentinal headache in those with an aneurysm
• Nausea and vomiting
• Meningism (photophobia, neck stiffness)
• Coma
• Seizures
• Sudden death
• ECG changes including ST elevation may be seen