Introduction

• Trauma is also a major cause, but is not considered true SAH.

Epidemiology and Aetiology

• Incidence is about 8 per 100 000
• Risk factors
  • ↑BP
  • Smoking
  • Known aneurysm – Or disease that causes aneurysm – e.g. polycystic kidney disease, co-arctation of the aorta, Ehlers-Danlos Syndrome
  • Family history – increases risk by 3-5x

Signs and Symptoms

• Sudden onset severe headache, often at the back of the head
• Neck stiffness – Kernig’s sign may be present after 6 hours (due to chemical meningitis), or in massive bleeds it may occur sooner due to herniation of the cerebellar tonsils (due to raised ICP).
  • Sometimes the chemical meningitis can cause vomiting and extensor plantar responses after 24hrs
• Impaired consciousness (drowsiness / coma) – usually occurs very shortly after the onset of symptoms, but can occur several hours later.
• Cranial nerve signs
• Hemiplegia
  • CNS deficits can become permanent within minutes. If it lasts more than several hours it is highly unlikely to ever resolve.
• Sentinel headache – is experienced by about 6% of patients, and is a prodromal headache thought to be the result of a small leak before rupture of an aneurysm or malformation.

Classification

Prognosis

• Overall mortality is 35-50%
  • About 30% die within a few days, and another 10-15% within a few weeks.
• Most patients die within 1 month
• After 1 month, 90% of patients will survive >1 year
• Prognosis is worse with aneurysm, better with AMV, and best when no lesion is detected (presumably the lesion was small, and has healed in these instances).

Pathology

• The period of haemorrhage is actually very short – and it normally stops bleeding by itself.
• After the initial haemorrhage, patients are at risk from vasospasm. This can causes ischaemia, which can result in secondary brain damage and further neurological signs.
  • 25% of patients will have signs of TIA / stroke after SAH as a result of vasospasm
  • Brain oedema and risk of vasospasm is greater between 72hrs and 10 days
• Secondary acute hydrocephalus often occurs
• Re-bleeding is VERY COMMON and usually occurs within 7 days. The risk thereafter is about 3% / year

Investigations

CT – is able to detect >90% of lesions within 48 hours of onset of symptoms.

• Often star shaped lesion on CT – or the blood fills in giral patterns around the brain the ventricles
• If CT is negative, but SAH is highly suspected, consider :

Lumbar puncture – contraindicated in raised ICP – so be careful! – Several features:

• Blood – detected via the presence of bilirubin. Previously, people would use the level of RBCs as an indicator, however, it is unreliable to use the rule: if blood remains constant in 3 separate samples = SAH, if blood declines = tap trauma.
• Xanthochromia – yellow appearance of CSF if it is left to stand for a few hours

Treatment

• Get specialist help! – call the Medical Registrar, the Neurosurgeon on call, and depending on GCS, call the anaesthetist. (Patients are unable to maintain a competant airway at GCS <8)
• Stablise the patient haemodynamically
• Many patients require ICU treatment
• Neurosurgical interventions are limited, but in severe cases, a drain may be placed.
• After the acute presentation, the patient may have their aneurysm clipped or coiled to prevent further bleeds

References

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