Neuroimaging in presumed primary headache disorders.

As routine outpatient neuroimaging became available more than 20 years ago, controversy arose over appropriate selection of patients for computed tomography studies and subsequently magnetic resonance imaging studies. Nowhere is this more apparent than in headache. Because headache is a truly ubiquitous condition with a lifetime prevalence rate reaching 90%, it is clear we cannot scan all patients with headache. Review of the pertinent literature, expert consensus, and a Practice Parameter issued by the American Academy of Neurology all suggest that routine neuroimaging is not necessary in patients with migraine headaches as defined by the International Headache Society criteria. The literature would also support the belief that imaging is not necessary in patients with typical recurrent cluster headaches. However, patients with new-onset headaches, headaches with a progressive course, headaches with a significant change in pattern, headaches that never alternate sides, and headaches associated with any neurologic findings or seizures have a substantially higher likelihood of a secondary cause such as tumor, arteriovenous malformation, or other structural lesion. In these situations, imaging must be considered as part of the workup. Unfortunately, the literature does not provide enough data to make any statistically predictive observations in patients with headaches other than migraine or cluster headache with symptoms but no findings on neurologic examination.