Red flags and comfort signs for ominous secondary headaches.

Secondary headaches are classified by the cause of the underlying disease process that is causing the headache. There are hundreds of secondary headache diagnoses and this article is not an exhaustive discussion of secondary headache disorders. Maintaining a high level of virulence and having a structured approach to evaluating all patients with headache is the key to timely diagnosis of secondary headache disorders. Diagnostic testing is indicated based on the suspected disorder and management is determined by treatment of the underlying disease causing the headache.