Secondary nummular headache: a literature review

Introduction: Despite being recognized only as a primary headache, some studies in the literature suggest the existence of nummular headache secondary to structural lesions and other diseases. The aim of this literature review is to compile the cases of probable secondary nummular headache reported in the literature. Methods: The terms "nummular headache" and "coin-shaped headache" were searched in five databases (MEDLINE, Scopus, SciELO, LILACS and Cochrane Library). Only articles that described cases of patients diagnosed with nummular headache were included. The cases were considered as secondary when a cause for the headache was suggested by the authors. Results: After excluding reviews and non-related or duplicated studies, 50 articles were included. A total of 343 cases of nummular headache were, at least, mentioned by these studies, and 30 of them were considered as secondary. Conclusion: there are few reports of secondary nummular headache in the literature; still, they represent a considerable percentage of the reported cases of nummular headache. They support that structural lesions and other diseases should be considered in the differential diagnosis of primary nummular headache.