ANSWER 1

1. True. The frequency of sentinel headaches preceding confirmed subarachnoid haemorrhage ranges widely in studies from 10–43%.1 This variability is only partly explained by recall bias. A recent review recommends that the term sentinel bleed should be abandoned: “people have either had a subarachnoid haemorrhage or not and the important task is to recognise when they have.”2

2. False. The false negative rate is approximately 2% when performed within 12 h, increasing to 7% by 24 h. Subarachnoid blood is almost completely reabsorbed at 10 days.2

3. False. There is currently no sound …