Subarachnoid haemorrhage

Question 1

Define subarachnoid haemorrhage.

Answer 1

Subarachnoid haemorrhage (SAH) is bleeding into the subarachnoid space and is an emergency. The most common cause of non-traumatic SAH is intracranial aneurysm. Aneurysmal SAH causes substantial morbidity and mortality. When a cerebral aneurysm ruptures, blood flows into the subarachnoid space, sometimes seeping into brain parenchyma and/or ventricles. The sudden increase in intracranial pressure, as well as the destructive and toxic effects of blood on brain parenchyma and cerebral vessels, accounts for most complications.

Question 2

Explain the aetiology/risk factors of subarachnoid haemorrhage.

Answer 2

Rupture of an intracranial saccular aneurysm is the leading cause of non-traumatic SAH, accounting for approximately 80% of cases. The remaining 20% are attributed to non-aneurysmal perimesencephalic SAH, arteriovenous malformations, arterial dissections, use of anticoagulants, and other rare conditions.

Question 3

Summarise the epidemiology of subarachnoid haemorrhage.

Answer 3

The incidence of SAH in most populations is between 6 and 8 cases out of 100,000 per year. In the UK, just over 9000 cases were reported in 2012-2013.
SAH accounts for about 5% of all strokes.

Question 4

Recognise the presenting symptoms of subarachnoid haemorrhage. Recognise the signs of subarachnoid haemorrhage on physical examination.

Answer 4

Headache
Photophobia
Loss of consciousness

Question 5

Identify appropriate investigations for subarachnoid haemorrhage and interpret the results.

Answer 5

CT - May also show subdural or parenchymal haematoma, hypodensities, hydrocephalus, and sometimes the aneurysm(s) if large or thrombosed.
FBC
Clotting profile
Serum electrolytes
Troponin I
ECG