Bifocal pain in nummular headache: A clinical analysis and literature review

Background: Nummular headache is a new category of primary headache disorder characterized by consistent location, size, and shape of painful areas. The pathogenesis is uncertain. Bifocal painful areas are rare manifestations but may expand the clinical diversity of nummular headache. Methods: The clinical characteristics of 5 bifocal nummular headache patients were reported and those of 11 patients in previous studies were reviewed. Bifocal nummular headache was classified into two types. Type I was defined as a simultaneous activation of two painful areas while type II was defined as two painful areas occurring in different times. Results: All 16 patients were female, with mean age of onset and initial presentation of 54.7 years and 58.2 years, respectively. There were seven type I and nine type II patients. The parietal area, especially the tuber parietale, was the leading site of involvement in both types of patients. The shape and size of painful areas were also similar between these two groups. There was an equal frequency of ipsilateral and contralateral painful areas. The pain intensity was similar in both types of patients but was milder in new painful areas than in previous painful areas in type II patients. Conclusions: Bifocal nummular headache suggests a central role of nummular headache but does not debunk the peripheral theory of nummular headache. The accumulated findings in bifocal NH patients do not support a generalization of pain occurrence or a reproduction of local process of epicranial neuralgia at multiple sites in nummular headache.