Non-traumatic subarachnoid haemorrhage (SAH) accounts for about 5% of all strokes with an incidence in Western populations of 6-10 cases per 100,000 person years [1-3].
Many people die from SAH before reaching hospital  and the overall case fatality rate is 45-50% [5,6]. Of those that do survive about a third are significantly disabled  both physically and cognitively.
Compared with other types of stroke, SAH affects a younger age group  (mean 50 years) and thereby has an even greater impact in terms of human and financial cost.
Patients with SAH are likely to present to the emergency department (ED) but misdiagnosis is often a problem [8,9]. Misdiagnosis of SAH is most likely in the neurologically pristine , the very population who have most to gain from timely treatment, with resultant human, financial and litigation cost . Correct and early diagnosis is vital as it enables early definitive treatment and improved clinical outcomes .
The overall mortality of SAH is 50%. Of survivors, one-third are significantly disabled [1-7].