- 5% of all acute strokes. Case fatality rate 50% overall (10-15% pre-hospital), up to 50% survivors residual disability and 50% ‘good’ outcomes have neuropsychological and cognitive impairment.
- Initially misdiagnosed in 12-50% as ‘migraine’ or ‘tension-headache’, as headache can abate or disappear. Up to 15% re-bleed early, and 40% in next 4 weeks.
- Sudden, instantaneous onset, maximum within minutes “worst headache ever”; generalised and unrelenting. Associated vomiting, neck pain, meningismus, altered mental status (>60%), and localising neurological signs incl III N with PCA aneurysm. May collapse (syncopal episode) then recover.
- Overall one in 100 headache patients seen in ED will have SAH, and up to 10% of those with severe, abrupt-onset headache.
- Atypical presentation: low grade fever, neck or back pain, seizures (7%), coma (up to 30%), focal stroke, restlessness, confusion or delirium.
Kowalski R, Claassen J, Kreiter K et al. Initial misdiagnosis and outcome after subarachnoid haemorrhage. JAMA 2004; 291: 866 -9. [Reference]
- CT scan (thin < 3 mm cuts without contrast)
- First line investigation. Over 95% – 98% positive in first 12 hrs, 93% by 24 hrs, but drops to 50% by day 7.
- May indicate site of bleed, early complications eg. hydrocephalus and cerebral oedema, or an alternative diagnosis.
- Lumbar Puncture (LP)
- If CT is negative (risk up to 5% patient still has SAH, but accuracy of modern multislice CTs is likely much higher).
- Check for xanthochromia by spectrophotometry of spun CSF, shielded from light.
- Perform LP 12 hours post headache to most reliably differentiate from a traumatic tap (absence of xanthochromia and bilirubin). Minimum 6 hrs.
- Note complications of LP include post-LP headache (up to 40%), low back pain, local infection or traumatic neurology, and traumatic tap with difficulty in interpretation.
Boesiger B, Shiber J. Subarachnoid hemorrhage diagnosis by computed tomography and lumbar puncture: are fifth generation CT scanners better at identifying subarachnoid hemorrhage? J Emerg Med 2005; 29:23-7. Also Best Bets evaluation [Reference]
Schwartz D. Feedback: Computed tomography and lumbar puncture for the diagnosis of subarachnoid haemorrhage: The importance of accurate interpretation. Ann Emerg Med 2002; 39: 190-2 [Reference] (Editorial BMJ March 2008 [Reference])
- CT angiography (CTA) if CT or LP positive, or if the diagnosis is still uncertain, to determine cause. Note up to 2% population may have an ‘incidental’ aneurysm anyway.
- Digital subtraction angiography (DSA) gold standard, but is invasive; or possibly proceed to MRA particularly for suspected partial thrombosis or spinal cord / brain stem origin.
- Airway, oxygen, analgesia, hydration, blood pressure control with labetalol IV, and ICU care for possible pulmonary oedema, arrhythmias, SIADH etc.
- Nimodipine 60 mg po 6-hrly upon confirmation of diagnosis if BP stable, or 1 mg/h IV increased to 2 mg/h after 2 hours if comatose.
- Reduces vasospasm by up to 50% and delayed ischaemic deficit by up to 60%, by vasodilating and protecting against reperfusion injury from calcium influx.
- Endovascular platinum coils (GDCs) now most common management.
- Alternative is early surgery if patient presents within 2-3 days of onset. Or may be delayed up to 14 days if spasm and infarction occur.
Edlow J, Malek A, Ogilvy C. Aneurysmal subarachnoid haemorrhage: update for emergency physicians. J Emerg Med 2008;34:237-51. [Reference]
van Gijn J, Kerr R, Rinkel G. Subarachnoid haemorrhage. Lancet 2007; 369: 306-318. [Reference]
Al-Shahi R, White P, Davenport R et al. Subarachnoid haemorrhage. BMJ 2006; 333:235-40. [Reference]
Suarez J, Tarr R, Selman W. Aneurysmal subarachnoid hemorrhage. N Eng J Med 2006; 354:387-96. [Reference]
Kirkpatrick P. Subarachnoid haemorrhage and intracranial aneurysms: What neurologists need to know. J Neurol Neurosurg Psych 2002; 72(Suppl I): i28-i33 [Reference]