Wednesday, 6 October 2010

MRCP revision battle 25.3: Subarachnoid haemorrhage

Subarachnoid haemorrhage is bleeding into the space between the subarachnoid membrane and the pia mater.

It accounts for 5-10% of all strokes.

  • ruptured berry aneurysm (80%)
  • malformations (15%)
  • post trauma

Common sites of berry aneurysms are:
  • junction of the posterior communicating artery with the internal carotid
  • junction of the anterior communicating artery with the anterior cerebral artery
  • the bifurcation of the middle cerebral artery

If (like me) your anatomy of the circle of willis is a little rusty the wiki commons image below might help refresh your memory:

15% of berry aneurysms are multiple.

Subarachnoid haemorrhages are associated with:
  • polycystic kidneys
  • coarctation of the aorta
  • Ehlers-Danlos syndrome
  • PAN

Classical presentation is a thunderclap occipital headache "as if kicked in head" with vomiting and neck stiffness.
Around 6% of patients will have had a sentinel headache before.

Investigation is:
  • CT - >90% of bleeds detected
  • LP - done >12hrs after onset looking for xanthochromia

  • neurosurgical referral
  • prompt angiography if surgery likely
  • nimodipine

On to another neuro topic - normal pressure hydrocephalus