Subarachnoid haemorrhage (SAH)
NICE guideline [NG228] Subarachnoid haemorrhage caused by a ruptured aneurysm: diagnosis and management. Published Nov 2022 NICE states that the guideline only covers the scope of aneurysmal SAH (i.e. SAH secondary to a ruptured aneurysm).
Guidelines
Important red flag symptom for SAH:
Other features of SAH:
Other features of SAH:
- Meningisim (triad of neck stiffness + photophobia + headache)
- Limited / painful neck flexion
- Nausea and vomiting
- Altered brain function
The diagnostic pathway can be split into 2 steps:
- First, confirm SAH
- Then, confirm whether SAH is secondary to an aneurysm or not
1st line investigation: non-contrast CT head ASAP
6 hours is the cut-off to guide subsequent actions if CT unable to diagnose SAH:
- → diagnose SAH
- Scan -ve → subsequent actions depends on timing of the scan
6 hours is the cut-off to guide subsequent actions if CT unable to diagnose SAH:
- Scan done within 6 hours → consider alternative diagnosis (SAH unlikely)
- Scan done after 6 hours → lumbar puncture to be performed at least 12 hours after symptom onset
- If → diagnose SAH
- If lumbar puncture -ve → consider alternative diagnosis (SAH unlikely)
In short, SAH can be diagnosed in the following scenarios:
- CT head showing blood in the subarachnoid space
- -ve CT head that is performed >6 hours after symptom onset but a +ve lumbar puncture (xanthochromia), that is performed >12 hours after symptom onset.
Non-contrast head CT's diagnostic accuracy for SAH is highest within 6 hours of symptom onset. After 6 hours, it is less reliable in diagnosing SAH, therefore LP is needed to rule in / rule out SAH.
Why LP should be performed 12 hours after? It takes time for blood to be broken down into bilirubin to give xanthochromia.
The following investigations to be performed without delay once SAH is confirmed:
- 1st line: CT angiography
- 2nd line: MR angiography / digital subtraction angiography
It is important to determine whether SAH is secondary to a ruptured aneurysm or not, as it would affect management.
Nimodipine (oral route preferred over IV)
- Calcium channel blocker
- Prevents vasospasm secondary to SAH
Do not offer pharmacological VTE prophylaxis to people with ruptured cranial vascular malformations (for example, brain aneurysms) or people with intracranial haemorrhage (spontaneous or traumatic) until the lesion has been secured or the condition has stabilised.
Options:
- Endovascular coiling (minimally invasive procedure performed by interventional neuroradiologist) - catheter guided to the aneurysm and coils are placed to promote thrombosis within the aneurysm sac.
- Neurosurgical clipping (open surgery performed by neurosurgeon) - via craniotomy, a clip is placed at the neck of the aneurysm.
- No intervention with monitoring
If interventional treatment is planned, ensure that it is carried out at the earliest opportunity to prevent rebleeding. Be aware that the risk of rebleeding is highest within 24 hours of the onset of symptoms.
Regarding the choice between endovascular coiling and neurosurgical clipping, NICE guideline does not explicitly state a preference, instead it emphasises planning based on 1) aneurysm characteristics, 2) patient factors, 3) availability of expertise. The AHA guideline advocates the same but also provides some extra points:
- Endovascular coiling is often preferred for aneurysms located in the posterior circulation or with narrow necks
- Neurosurgical clipping might be more appropriate for aneurysms with wide neck / complex configurations
Simplified Flow Chart
References
