Subarachnoid haemorrhage

About 75% of patients with subarachnoid haemorrhage present with acute severe headache, and the rest present with loss of consciousness. The mortality is high, and many patients die before reaching hospital.

About 20% of patients with subarachnoid haemorrhage have a sudden headache several weeks before the acute event. This is thought to be due to a sentinel bleed, which is a minor subarachnoid bleed before the main rupture. It is a warning sign that must be investigated. If diagnosed at this early stage, the aneurysm can be treated while the patient is still clinically well.

Patients with suspected subarachnoid haemorrhage need urgent evaluation in hospital. If subarachnoid blood is seen on a computed tomography (CT) scan, this is diagnostic. However, a normal CT scan does not exclude subarachnoid haemorrhage. If the CT scan is normal but the index of suspicion is high, perform a lumbar puncture, or arrange urgent magnetic resonance imaging to look for blood products in the cerebrospinal fluid space.

In hospital, patients are managed by a neurosurgeon, in close collaboration with an interventional neuroradiologist, and occasionally with a neurologist. Most subarachnoid haemorrhages are due to a ruptured intracranial aneurysm, and management is to treat the aneurysm (surgically or endovascularly) and identify and treat the consequences of the bleed. Delayed cerebral ischaemia is the main complication.