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Subarachnoid haemorrhage

  • Subarachnoid haemorrhage accounts for approximately 5% of CVAs
  • Outcome depends on the degree of neurological deficit
  • The lower the GCS on presentation the worse the prognosis
  • 70% are due Berry aneurysms
  • 10% are due to arteriovenous malformations
  • 10% are due to hypertension
  • 5% are idiopathic

Pathology of Berry aneurysms

  • Aneurysms are found in 8% of individuals at post mortem
  • They are thin walled saccular aneurysms found at arterial bifurcations
  • Occur due to turbulent flow and damage to internal elastic lamina
  • Commonest site of aneurysms are:
    • Posterior communicating artery 30%
    • Anterior communicating artery 25%
    • Middle cerebral artery 25%
  • Estimated to have a population prevalence of 1.5%
  • Most remain asymptomatic but they are a common cause of sudden death

Clinical features

  • Classic presentation is with a sudden onset of severe headache

  • Often assocaited with nausea, vomiting, photophobia and neck stiffness
  • Neurological symptoms and signs may be present
  • Level of consciousness may be reduced
  • Fundoscopy may show subhyoid haemorrhages
  • The clinical course is unpredictable
  • Overall mortality is approximately 40%
  • Many patients die before reaching hospital

Investigations

  • Diagnosis can often be confirmed by an early CT
  • Has a sensitivity of 90% if performed within the first 24 hours
  • Sensitivity reduced to 50% by 72 hours as blood is reabsorbed
  • CT may also identify source of haemorrhage
  • If diagnosis is on doubt then lumbar puncture may be indicated
  • Will show uniform blood-staining of CSF and xanthochromia
  • Cerebral angiography will identify site of an aneurysm
  • 15% of aneurysms are multiple

Complications

  • The major complications are:
    • Rebleeding
    • Delayed ischaemic neurological deficit
    • Hydrocephalus
  • Risk of rebleed is 4% at 24 hours, 25% at 2 weeks and 60% at 6 months
  • Rebleeding is associated with a 60% mortality
  • Delayed ischaemic neurological deficit (DIND) is due to intense vasospasm
  • Treatment is by maintaining cerebral perfusion with adequate hydration
  • Calcium channel blocks may also be useful
  • Hydrocephalus results from impaired CSF reabsorption through arachnoid villi
  • 10% of patients will require CSF diversion or shunting

Management

  • In patients fit for surgery the aneurysm should be clipped at craniotomy
  • Aim is clip neck of aneurysm whilst maintaining flow in native vessel
  • May also be embolised endovascularly with platinum coils
  • Timing of intervention is controversial
  • Vasospasm usually greatest at 5 days
  • Surgery traditionally deferred until 10 days after the initial bleed
  • Patients may die as a result of rebleed during this period
  • Early surgery may be associated with reduced mortality and no increased morbidity

Bibliography

Al-Shahi R,  White P M,  Davenport R J et al.  Subarachnoid haemorrhage.  BMJ 2006;  333:  235-240

Edlow J A,  Caplan L R.  Avoiding pitfalls with the diagnosis of subarachnoid haemorrhage.  N Engl J Med 2000;  342:  29-36.

van Gijn J,  Kerr R S,  Rinkel G L.  Subarachnoid haemorrhage.  Lancet 2007;  369:  306-318.
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