Subarachnoid haemorrhage

Question 1

What is a subarachnoid haemorrhage (SAH)?

Answer 1

A subarachnoid haemorrhage (SAH) is an intracranial haemorrhage defined as the presence of blood within the subarachnoid space, deep to the subarachnoid layer of the meninges.

Question 2

What is the most common cause of SAH?

Answer 2

The most common cause of SAH is head injury, termed traumatic SAH. In the absence of trauma, it is called spontaneous SAH.

Question 3

What are the causes of spontaneous SAH?

Answer 3

Causes of spontaneous SAH include:
- Intracranial aneurysm (saccular ‘berry’ aneurysms)
- Arteriovenous malformation
- Pituitary apoplexy
- Mycotic (infective) aneurysms

Intracranial aneurysms account for around 85% of cases.

Question 4

What are the classical presenting features of SAH?

Answer 4

Classical presenting features include:
- Sudden-onset headache (‘thunderclap’)
- Severe headache (‘worst of my life’)
- Occipital headache
- Nausea and vomiting
- Meningism (photophobia, neck stiffness)
- Coma
- Seizures
- ECG changes including ST elevation

Question 5

What is the first-line investigation for SAH?

Answer 5

The first-line investigation of choice for SAH is a non-contrast CT head.

Question 6

What should be done if the CT head is normal within 6 hours of symptom onset?

Answer 6

If the CT head is normal within 6 hours of symptom onset, new guidelines suggest not doing a lumbar puncture and considering an alternative diagnosis.

Question 7

What is xanthochromia and why is it important?

Answer 7

Xanthochromia is the result of red blood cell breakdown and helps to distinguish true SAH from a ‘traumatic tap’. It is assessed in the CSF after a lumbar puncture performed at least 12 hours after symptom onset.

Question 8

What is the management for confirmed aneurysmal SAH?

Answer 8

Management includes supportive care, bed rest, analgesia, venous thromboembolism prophylaxis, discontinuation of antithrombotics, and prevention of vasospasm using oral nimodipine.

Question 9

What are the complications of aneurysmal SAH?

Answer 9

Complications include:
- Re-bleeding
- Hydrocephalus
- Vasospasm (delayed cerebral ischaemia)
- Hyponatraemia
- Seizures

Re-bleeding occurs in around 10% of cases, most commonly in the first 12 hours.

Question 10

What are important predictive factors in SAH?

Answer 10

Important predictive factors in SAH include:
- Conscious level on admission
- Age
- Amount of blood visible on CT head.

Question 11

Answer 11

Question 12

Answer 12

Question 13

NICE flowchart showing investigations of suspected subarachnoid haemorrhage

Answer 13