Some life threatening brain disorders present with secondary headache, where the headache is caused by the disease. A brain tumour, for example, is best diagnosed by brain imaging early in the course of the disease, which is essential for optimal management of this and other secondary headache disorders. However, brain tumours, as an example, account for less than 0.1% of the lifetime prevalence of headache.1 This contrasts with the fact that most headaches in the community are either associated with mild systemic infection or due to primary headache,1 where the headache is itself the disorder. Dissecting primary from secondary headache is the problem, since, by definition, primary headache does not need brain imaging because no disease process exists that leads to macroscopic change in general terms.

How does one dissect primary from secondary headache? This question can have only a clinical response since no controlled trials have been conducted to identify causes of secondary headache. In clinical practice we generally accept that the so called red flags of headache should trigger a search for secondary headache.2 Thus change in the pattern of headache; new …