Subarachnoid Haemorrhage

Question 1

What is xanthochromia and how soon after an SH does it appear?

Answer 1

Straw-coloured CSF caused by presence of breakdown products of haemoglobin
- requires at least 6 hours before detection

Question 2

How sensitive is an LP in subarachnoid haemorrhage diagnosis?

Answer 2

95% sensitive when spectrophotometry is used to look for xanthochromia

Question 3

What causes focal weakness in SH, and how does it cause it?

Answer 3

Haematoma or arterial construction/occlusion 4-12 days post-event
- surrounding blood clot, oedema, and inflammatory factors induce vasoconstriction and further vessel inflammation, potentially resulting in ischaemic brain damage

Question 4

Do subarachnoid haemorrhages present with new seizures?

Answer 4

Yes - 10% of cases making it to hospital present with new seizures

Question 5

What is a common cause of subarachnoid haemorrhage and how does it cause SH?

Answer 5

Extreme exertion or coitus

- sudden drastic increases in intracranial pressure can lead to cerebral aneurysm rupture

Question 6

How useful is unenhanced CT in SH diagnosis and when is it useful?

Answer 6

Very useful - shows 95% of subarachnoid haemorrhages within 48 hours

Question 7

What colour is blood on CT and why?

Answer 7

Relative but generally whiter than surrounding tissue

- due to increased density of radio-opaque iron