Brilstra 2000.

Methods	Method of randomisation: sealed envelopes Blinding of outcome assessment: no Analysis: intention to treat Excluded participants: 9 prior to randomisation Cross‐over cases: no Losses to follow‐up: at 1‐year follow‐up: 2 participants in the endovascular coiling group and 2 participants in the neurosurgical clipping group Definition of outcomes: stated
Participants	Location: University Medical Centre Utrecht and St Elisabeth Hospital Tilburg, The Netherlands Coiling: 10 (men: 3 (30%)) Clipping: 10 (men: 3 (30%)) Age range: 35–75 years Entry criteria: documented aneurysmal SAH by either CT or DSA within the preceding 4 days, clinical state justifying treatment, aneurysm suitable for both treatment modalities Comparability of treatment groups: good for major prognostic factors Clinical grade on admission: coiling: WFNS I: 4; II: 3; III: 1; IV: 2; V: 0 clipping: WFNS I: 4; II: 2; III: 2; IV: 1; V: 1 Aneurysm location: coiling: ACA and Acom: 5; MCA: 1; ICA: 4; posterior circulation: 0 clipping: ACA and Acom: 3; MCA: 2; ICA: 5; posterior circulation: 0
Interventions	Endovascular coiling Neurosurgical clipping
Outcomes	Clinical outcomes: dependency and death at 1‐year follow‐up (Rankin score 3–6), rebleeding, epilepsy, quality of life at 1 year and neuropsychological outcomes Additional measures: cost‐effectiveness
Notes	Exclusion criteria: the logistic conditions for early operation could not be fulfilled Follow‐up duration: 3 months and 1 year
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Used a computer‐generated list
Allocation concealment (selection bias)	Low risk	Allocation concealment performed by sealed envelopes that were not within reach of the treating physician.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Blinding of participants of personnel was not possible due to the characteristics of the interventions. However, review authors judged that the risk of performance bias was low.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Participants or their carers interviewed by telephone to assess functional outcome 3 months after SAH and 12‐month functional outcome assessed at outpatients clinic by a neurologist or by a neurosurgeon who had not operated on the participant. Unclear whether blinding was performed.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data complete for all outcomes
Selective reporting (reporting bias)	Low risk	Study protocol not available but it was clear that the obtained data include all expected outcomes, including those that were prespecified.
Other bias	Low risk	Other sources of bias not identified