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
- 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
- Clipping or coiling?
- For AVMs
- Surgery to remove, embolism or ‘gamma knife’ radiotherapy
- Follow up regularly with MRA or CT angio
Complications of subarachnoid haemorrhage
- Persistent neurological deficit
- Larger aneurysms, HTN, age, smoking and multiple aneurysms all predict this.
- 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
- 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