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Nummular headache: Peripheral or central? One case with reappearance of nummular headache after focal scalp was removed, and literature review

Background Nummular headache, or coin-shaped cephalagia, is defined as a mild to moderate, pressure-like pain that is felt exclusively in a circumscribed area. More than 200 cases of nummular headache have been reported since it was defined in 2002, but the pathogenesis remains unclear. Methods A patient with nummular headache who had the symptomatic area of his scalp removed but suffered headache reappearance was reported. All published cases of nummular headache in the English literature were reviewed and analyzed for demographic and clinical features, image and laboratory findings, and response to treatment. Results The patient with nummular headache had the symptomatic area of the scalp removed but suffered reappearance of headache in another area that overlapped with the former one. The literature review showed that nummular headache was a chronic, mild to severe, pressure-like pain with a circular or elliptical shape of 1–10 cm in diameter. The parietal region was the most affected region. Exacerbations and sensory disturbances in the affected area were reported in 43% and 56% of cases, respectively. Observational data suggested botulinum toxin type A (BoNTA) and gabapentin may be beneficial. Discussion Our case and evidence from the literature review support the peripheral mechanism of nummular headache. Nummular headache might be a local pain disorder stemming from terminal branches of a sensory nerve and could induce peripheral sensitization in one or several primary sensory neurons.