Pathophysiology
- Most commonly due to trauma.
- Spontaneous SAH are mostly caused by a rupture of intracranial aneurysm (75%). Can also be caused by AV malformations, vasculitis, coagulopathy.
- Aneurysms most commonly at junction between:
- posterior communicating and ICA
- anterior communicating and ACA
- bifurcation of MCA
- Aneurysms classically associated with:
- Polycystic kidney disease
- Ehlers-Danlos
- Aortic coarctation
Classic presenting complaint
- 55yo, female, Japanese/Finnish/Black descent
- Sudden onset “thunderclap” headache classically occipital
- Vomiting + photophobic + syncope
- PMH: poorly controlled HTN, smoker, cocaine use
On examination
- Reduced GCS – may not recover
- Meningism
- Nuchal rigidity
- Kernig’s sign (flex hip with knee bent, then extend knee – positive if pain in hamstring)
- Photophobia
- Ocular haemorrhage (? due to raised ICP)
- subhyaloid haemorrhage
- intra-retinal haemorrhage
- vitreous haemorrhage (=<25% of aneurysmal SAH)
- Unequal pupils – aneurysmal compression of CN III
Clinical approach & differential
- Benign thunderclap headaches (crash migraines) – no blood on CT/LP
- Reversible cerebral vasoconstrictive syndrome (RCVS) – vasculitis associated with previous use of vasoconstrictive agents
- Meningitis
- Migraine
- ICH
- Cortical vein thrombosis
Investigations
- Urgent non-contrast CT head
- If CT normal, LP in those with strong history
- 3 bottles + glucose bottle
- Xanthochromia
- microscopy, C&S, protein
Classic findings
CT sensitivity within 48h: 90-95%
High attenuation (blood) in the subarachnoid space, most obviously around the circle of Willis, basal cisterns or in the Sylvian fissure.
Prognosis
If due to aneurysm:
- 10% die before reaching hospital
- 10% mortality within first few days
- 45% mortality overall
If survives and not treated, risk of re-bleed within 2 weeks: 20%
Treatments
Plan
- ABC
- Elevate head of bed
- Consider mannitol +/- furosemide
- Treat seizures if required
- Nimodipine 4hourly or IVI
- Urgent neurosurgery referral
- Urgent ICU bed
- 1 hourly neuro-obs
- Aim systolic BP 120-150
- Fluids (beware cerebral salt wasting/SIADH – do not fluid restrict)
- Stool softeners
- NBM
Neurosurgical/vascular options:
- CTA or angiography
- Endovascular coiling
- Intraventricular catheter (venticulostomy) if hydrocephulus develops