In the absence of secondary headache, the clinician can proceed to diagnosing a primary headache disorder. If the headache is atypical or difficult to classify, the possibility of secondary headache should be reconsidered, although the modifying effect of any treatment should be kept in mind. Discussing the diagnostic criteria of primary headaches is beyond the scope of this clinical article. The objective of this section is to propose a strategy to approach the primary headaches, after excluding secondary disorders.
If a patient has acute headache and secondary headache syndromes have been excluded, either by clinical history or appropriate investigation, the next step is to assign the primary headache diagnosis. Patients can be divided into those whose headaches are of low-to-moderate frequency (fewer than 15 headache days per month) or those whose headaches are of high frequency (15 or more headache days per month). Based on average duration of a typical untreated headache attack, the headache syndrome is classified as either short-duration (less than 4 hours a day) or long-duration (4 or more hours) (Lipton et al 2004).