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Definition of subarachnoid haemorrhage (SAH)

  • Spontaneous bleeding into the subarachnoid space. SAH is the cause of 5% of strokes.


Epidemiology of subarachnoid haemorrhage

  • Incidence: 6-12 per 100,000 per year
  • Age: 50% are under 55
  • Sex: Men more common < 25, women generally more common (especially when >60)


Causes of spontaneous subarachnoid haemorrhage

  • Berry aneurysms  (70%)
  • Arteriovenous malformation (AVM) (10%)
  • No causative lesion found (20%)
    • Note that subarachnoid blood can also be found traumatically, this can be considered in the category of traumatic brain injury.


Risk factors for subarachnoid haemorrhage

  • Hypertension
  • Smoking
  • Excessive alcohol
  • Polycytic kidney disease (PKD)
    • 10% of them have aneurysms
    • PKD makes up 1% of SAH
  • Connective tissue disease
    • Pseudoxanthoma elasticum, Marfan’s disease, Ehlers-Danlos type 4, HHT
  • Hypertension, smoking and excessive alcohol all roughly double risk of SAH, and are modifiable.
  • Larger berry aneurysms are more likely to rupture.
    • As the vast majority are small, the average size is under 1cm diameter


Pathology of subarachnoid haemorrhage

  • Berry aneurysms tend to arise at arterial junctions in the Circle of Willis
    • Between posterior communicating and internal carotid: posterior communicating artery aneurysm.
    • Between anterior communicating and anterior cerebral arteries: anterior communicating artery aneurysm
    • At bifurcation of middle cerebral artery: middle cerebral artery aneurysm
  • The aneurysm then ruptures and blood goes into the subarachnoid space, leading to the symptoms.


General overview of subarachnoid haemorrhage.


Symptoms of subarachnoid haemorrhage

  • Classical presentation is a sudden onset ‘thunderclap’ headache, often described as the ‘worst headache in the world’, commonly occipital
    • However, the presentation is highly variable, so any acute severe headache should lead SAH to be high on your differential diagnosis list
  • Nausea and vomiting (prognostically poor if happens at onset)
  • Meningism [neck stiffness and photophobia due to meningeal irritation] (prognostically poor)
  • Seizures (only in 7% but highly suggestive)
    • Early seizures predict late seizures and poor outcome
  • New neurology (prognostically poor)
    • Diplopia is most common
    • Weakness, dizziness, ptosis, dysphasia
  • Reduced GCS in approx 60% (prognostically poor)
  • Papilloedema, retinal haemorrhages or subhyaloid haemorrhage in major haemorrhage
  • Prognostically poor features include:
    • Vomiting, hypertension, loss of consciousness at presentation, meningism, new clinical neurology


Differential diagnosis of subarachnoid haemorrhage

  • Non-sinister headaches
    • Tension headache
    • Cluster (often at night, clustered in time, unilateral, often post-ocular with eye watering)
    • Migraine (look for gradual onset, aura, past history, family history)
    • Benign coital headache can present exactly like this but with all investigations negative
  • Other sinister headaches
    • Tumour (gradually worsening, raised ICP symptoms)
    • Stroke (unilateral signs, stroke risk factors)
    • Venous sinus thrombosis (dehydration, OCP, previous clots)
    • Temporal arteritis (elderly, temporal tenderness, jaw claudication)
    • Meningitis or encephalitis
  • Other causes of coma


Investigations of subarachnoid haemorrhage

  • Immediate CT Head
    • Shows subarachnoid or ventricular blood
    • If no SAH on CT, lumbar puncture as long as scan doesn’t suggest raised ICP (i.e. mass lesion)
  • LP must be done 12 hours after SAH to be reliable
    • Need spectroscopy to confirm, xanthochromia is less used nowadays
    • Stays positive for two weeks with 100% sensitivity
  • MR angiography (or alternatively, CT angiography) is done immediately after SAH is confirmed to show location of aneurysms so that they can be repaired.
  • All the usual investigations including bloods (including coagulation studies and group and save) and ECG


Grading of subarachnoid haemorrhage

  • Hunt & Hess system
    • Grade 1 – asymptomatic or mild headache and slight nuchal rigidity
    • Grade 2 – severe headache, stiff neck, no neurologic deficit except cranial nerve palsy
    • Grade 3 – drowsy or confused, mild focal neurologic deficit
    • Grade 4 – stuporous, moderate or severe hemiparesis
    • Grade 5 – coma, decerebrate posturing.
  • Grades 1-3 should have digital subtraction angiography to see any other aneurysms and then have these sorted surgically. 4-5 don’t benefit from this (too bad prognostically anyway).


Treatment of subarachnoid haemorrhage

    • Intubation if necessary. Low threshold for ITU involvement
  • Supportive therapy
    • Fluids, controlled oxygen
    • Keep platelets over 100
  • Early discussion with neurosurgery (see below)
  • Reverse anticoagulation no matter what the indication for it
  • Rapid treatment of BP is not recommended. Keep systolic under 180 or MAP under 130. Aiming for systolic<140 (NEJM 2013).
    • If BP contol is needed acutely, ITU for labetolol is appropriate
  • Nimodipine 60mg 4hrly for everyone (prevents vasospasm)
    • Reduce dose to 30mg 4 hourly if bP 100-140; withold of BP under 100
    • If vasospasm occurs (stroke-like syndrome) consider:
  • 3H treatment (hypertension, hypervolaemia and haemodilution)


Surgery in subarachnoid haemorrhage

  • Absolutely all cases of SAH should ne referred to the neurosurgeons except in cases of extreme frailty where surgery would be inappropriate.
  • Decisions regarding surgery should be made by an expert neurological centre.
  • Surgery can involve urgent clipping or endovascular coiling
    • Clipping or coiling?
      • This is a complex decision and will be made on a case-by-case basis by the neurosurgeons.
      • ISAT trial: Coiling has less disability and epilepsy at seven years. More rebleeding though, and less complete occlusion on follow-up imaging. Coiling is difficult to do if very wide-necked.
    • Coiling should be done using 4-vessel DSA (digital subtraction MRA, sees carotids and vertebrals) in under 48 hours.
    • Clipping helps prevent cerebral ischaemia as the presence of subarachnoid blood is a powerful predictor of delayed cerebral ischaemia
  • For AVMs
    • Surgery to remove, embolism or ‘gamma knife’ radiotherapy
  • Follow up regularly with MRA or CT angio


Complications of subarachnoid haemorrhage

  • Death
  • Persistent neurological deficit
  • Re-bleeding
    • Larger aneurysms, HTN, age, smoking and multiple aneurysms all predict this.
  • Vasospasm
    • Leading to delayed cerebral ischaemia (hence nimodipine)
    • Most common at three days, can happen up to two weeks
      • Ealry clipping or coiling does NOT get rid of this
  • Epilepsy (in 5%)
    • Give antiepileptics if seizures, tapering down over 6 months if seizure-free
  • Raised intracranial pressure
    • Treat with mannitol
  • Hyponatraemia
    • Can be SIADH (treatment being fluid restriction) or cerebral salt-wasting (treatment being isotonic saline). May be difficult to distinguish


Prognosis following subarachnoid haemorrhage

  • Prognosis is generally bad
  • There is an 45% mortality within the first 24 hours
  • 10-20% of remainder rebleed and die within a few weeks
  • Of those who survive, there is significant morbidity
    • Reduced or unemployment in about 50%
    • Personality changes in ~50%.
  • 25% of survivors recover completely