- Mortality rates currently 35-50% (incidence varies highly in studies)
- Of those that die:
- ~15% die prior to reaching hospital
- 60% die within first 24 hours
- 19% die within 1 week
- 6% die within 3 weeks
- 1% die later than 3 weeks
- High long term morbidity for survivors:
- ~ 20-30% will be dependent on carers
- Up to half have cognitive impairment sufficient to affect quality-of-life
- Prognosis worsens with increasing severity grade (Glasgow outcome scale 1-3 or modified Rankin scale 4-6):
WFNS (World Federation of Neurosurgical Societies) Grade
Proportion with Bad Outcome
I
14.8%
II
29.4%
III
52.6%
IV
58.3%
V
92.7%