Subarachnoid haemorrhage Flashcards
Define subarachnoid haemorrhage (SAH)
Spontaneous bleeding into the subarachnoid space (between arachnoid mater and pia mater), often catastrophic
How common is it? Who gets SAH?
Incidence 9/100 000/yr;
Typical age: 35–65.
- 6x more common in women
- 1x more common in black ethnicity
What % of strokes is caused by SAH?
5%
What are the risk factors for SAH?
- previous aneurysmal SAH
- HTN
- Smoking
- FH - x3-5
- ADPKD (autosomal dominant polycystic kidney disease)
- alcohol
- cocaine
- bleeding disorders
- Marfan syndrome/ Ehlers Danlos syndrome
- Aortic coarctation
- Pseudoxanthoma elasticum
- Neurofibromatosis type I
- SBE (mycotic aneurysms)
*Many of these genetic syndromes are associated with Berry aneurysms.
What is the aetiology of SAH?
80% - rupture of intracranial saccular aneurysms (non-traumatic)
20% - non-aneurysmal perimesencephalic SAH, arteriovenous malformations, arterial dissections, use of anticoagulants, and other rare conditions
Where do most cerebral aneurysms occur?
Cerebral aneurysms arise at the bifurcation of major arteries that form the circle of Willis. The majority are located at:
- anterior communicating/anterior cerebral artery junction (Acom/ACA),
- distal internal carotid artery/posterior communicating artery junction (ICA/Pcom),
- and middle cerebral artery bifurcation (MCA).
What are the symptoms associated with SAH?
- Sudden onset excruciating headache, typically occipital (“thunderclap”) - often lasting 1-5min. Speed of onset is diagnostic.
- Sometimes preceded by a “sentinel” headache - perhaps from small warning leak from offending aneurysm (80%)
- Vomiting
- Collapse
- Seizure
- Coma/drowsiness may last for days
- Photophobia
- Confusion
What are the signs of SAH on examination?
- Neck stiffness
- Kernig’s sign (takes 6h to develop)
- Retinal, subhyaloid and vitreous bleeds (Terson’s syndrome; increased mortality ~5)
- Focal neurology may suggest aneurysm site (e.g. pupil changes = 3rd nerve palsy with PCA aneurysm) or intracerebral haematoma
Which conditions present similarly?
- Meningitis
- Migraine
- Intracerebral bleed
- Cortical vein thrombosis
- Dissection of carotid/vertebral artery
- Benign thunderclap headache (triggered by Valsalva maneouvres eg cough, coitus)
What investigations would you do for subarachnoid haemorrhage? Describe when these should be done.
- Urgent non-contrast CT - detects >95% of SAH within 1st 24hrs
- LP - if CT is negative but history is suggestibe of SAH. Needs to be done >12hours after headache onset to allow RBC breakdown for +ve xanthochromic sample (yellow, due to bilirubin differentiates between old blood from SAH vs “bloody tap”)
Other:
- Electrolytes - may show hyponatraemia (<131mmol/L)
- FBC - leukocytosis in SAH common
- Clotting profile - elevated INR and PTT time
- Troponin I - may be elevated but less than in MI
- ECG - half of all patients have abnormal ECG on admission. Common cardiac findings in SAH include: Arrhythmias and ischaemic changes// Prolonged QTc // ST segment/T-wave abnormalities.
How do you manage SAH? (not on Sofia)
Refer all to neurosurgery .
Re-examine CNS often; chart BP, pupils, and GCS. Repeat CTif deteriorating.
Maintain cerebral perfusion by keeping well hydrated, but aim for SBP <160mmHg.
Nimodipine (60mg/4h PO for 3wks, or 1mg/h IVI) is a Ca2+ antagonist that reduces vasospasm and consequent morbidity from cerebral ischaemia.
Surgery:
- endovascular coiling vs surgical clipping (requiring craniotomy): the decision depends on the accessibility and size of the aneurysm, though coiling is preferred where possible (fewer complications, better outcomes).
- Do catheter or ct angiography to identify single vs multiple aneurysms before intervening.
- Newer techniques such as balloon remodelling and flow diversion can be helpful in anatomically challenging aneurysms.
