Subarachnoid Haemorrhage (SAH)

In patients under 20 years of age, arteriovenous (AV) malformations are the commonest cause of non-traumatic cases. In older patients, rupture of a cerebral artery aneurysm is the usual cause.

Known risk factors

Known risk factors include:

  • Female gender
  • Hypertension
  • Positive family history
  • Polycystic kidney disease


Classic presentation of a sudden severe ‘thunderclap’ headache is often described as ‘my worst ever headache’. This is associated with nausea, vomiting, photophobia or neck stiffness.

Neurological symptoms

Neurological symptoms may occur such as:

  • Seizures
  • Diplopia
  • Brief loss of consciousness
  • Reduced level of consciousness

On examination, 70% of patients have neck stiffness and 20% have a focal neurological deficit.

The commonest neurological deficit is a cranial nerve (CN) III nerve palsy.

In severe cases, retinal haemorrhage may be seen.

Hunt and Hess scale for grading SAH

Table 1 Hunt and Hess Scale for grading SAH
Scale Symptom
1 Asymptomatic, or minimal headache and slight nuchal rigidity
2 Moderate to severe headache, nuchal rigidity and no neurological deficit except cranial nerve palsy
3 Drowsy, minimal neurological deficit
4 Drowsy, significant neurological deficit
5 Deep coma, decerebrate rigidity and moribund appearance

Important: Overall, approximately 50% of patients die from the immediate haemorrhage, or as a consequence of secondary complications, and 50% of the patients who survive are rendered seriously disabled. In patients with an SAH, the outcome is directly related to the neurological status at presentation.

More information on this subject can be found in the session about subarachnoid haemorrhage.