Subarachnoid haemorrhage Flashcards
What is a subarachnoid haemorrhage (SAH)?
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.
What is the most common cause of SAH?
The most common cause of SAH is head injury, termed traumatic SAH. In the absence of trauma, it is called spontaneous SAH.
What are the causes of spontaneous SAH?
Causes of spontaneous SAH include:
1. Intracranial aneurysm (saccular ‘berry’ aneurysms)
2. Arteriovenous malformation
3. Pituitary apoplexy
4. Mycotic (infective) aneurysms
Intracranial aneurysms account for around 85% of cases.
What are the classical presenting features of SAH?
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.
What is the first-line investigation for SAH?
The first-line investigation of choice for SAH is a non-contrast CT head.
What does acute blood appear as on a CT scan for SAH?
Acute blood appears hyperdense/bright on CT, typically distributed in the basal cisterns, sulci, and in severe cases, the ventricular system.
What should be done if a CT head is normal within 6 hours of symptom onset?
If a CT head is normal within 6 hours of symptom onset, new guidelines suggest not doing a lumbar puncture and considering an alternative diagnosis.
What is xanthochromia and its significance in SAH?
Xanthochromia is the result of red blood cell breakdown and helps distinguish true SAH from a ‘traumatic tap’.
The lumbar puncture should be performed at least 12 hours after symptom onset to allow for its development.
What is the management for confirmed aneurysmal SAH?
Management includes supportive care, bed rest, analgesia, venous thromboembolism prophylaxis, discontinuation of antithrombotics, and prevention of vasospasm with oral nimodipine.
What are the complications of aneurysmal SAH?
Complications include:
- Re-bleeding
- Hydrocephalus
- Vasospasm (delayed cerebral ischaemia)
- Hyponatraemia
- Seizures.
What are important predictive factors in SAH?
Important predictive factors in SAH include:
- Conscious level on admission
- Age
- Amount of blood visible on CT head.
NICE flowchart suspected subarachnoid hemorrhage
