19th July 2023

Subarachnoid haemorrhage (SAH)

Background

SAH is a type of intracranial haemorrhage where bleeding occurs in the subarachnoid space. It can be classed as a type of stroke, which accounts for ~5% strokes. Most commonly, a spontaneous SAH is caused by a ruptured aneurysm. Other causes include arteriovenous malformations and arterial dissection.

Risk factors include family history of SAH, smoking, hypertension and excess alcohol intake.

Classically SAH presents as a sudden onset ‘thunderclap’ headache which reaches peak intensity within minutes. Other features can include nausea, vomiting, meningism and loss of consciousness.

Investigations

Recommended investigations include immediate CT brain imaging and lumbar puncture (LP). If the CT scan is negative and shows no contraindication to an LP, it is performed 12 hours after symptoms onset to investigate for xanthochromia.

Further imaging to consider would be CT or MR angiography to assess for the cause and potential intervention

Management

Patients with confirmed spontaneous SAH should receive nimodipine, have frequent neurological observations and be referred to a neurosurgical centre.

Complications

Complications include rebleeding, vasospasm and delayed cerebral ischaemia, hydrocephalus, seizures and neuropsychiatric sequelae.