Treatment outcomes in primary nummular headache: a systematic review.

Background: Nummular headache is a rare primary headache disorder characterized by pain strictly confined to a small, coin-shaped area of the scalp. In the absence of standardized treatment guidelines, management relies on heterogeneous, low-level evidence. Objectives: To systematically synthesize the available evidence on treatment outcomes in primary nummular headache, focusing on complete remission, clinically meaningful response (≥50% improvement), and treatment tolerability. Methods: This systematic review followed PRISMA guidelines and was registered in PROSPERO (CRD420261375695). Five electronic databases were searched from inception to March 2026 for studies including ≥5 patients with primary nummular headache according to ICHD criteria. The primary outcome was complete remission; secondary outcomes included ≥50% clinical response and discontinuation due to adverse events. A descriptive synthesis was performed because of substantial clinical and methodological heterogeneity. Risk of bias was assessed with the Newcastle-Ottawa Scale and Joanna Briggs Institute checklists. Results: Thirty-seven studies (1,012 patients) were included, predominantly case reports, case series, and uncontrolled observational cohorts. OnabotulinumtoxinA was the most robustly evaluated intervention, achieving complete remission in 47.5%-48.8% and ≥50% response in 62.5%-77.4% of patients, with no reported treatment discontinuations due to adverse events. Gabapentin showed complete remission rates of 35.2%-45.5% and ≥50% response rates of 43.7%-65.7%, but was associated with a 21.1% discontinuation rate because of adverse effects. Evidence for amitriptyline, lamotrigine, pregabalin, and other therapies was limited to smaller samples and showed variable efficacy. Outcome definitions varied considerably across studies, and no randomized comparative trials were identified. Conclusion: Current evidence suggests that onabotulinumtoxinA offers the most favorable efficacy-tolerability profile, while gabapentin is effective but limited by tolerability concerns. The overall evidence base remains predominantly uncontrolled and heterogeneous. Prospective comparative studies with standardized outcome measures are urgently needed to establish definitive treatment guidelines for this disabling headache disorder. Systematic Review Registration: Identifier CRD420261375695.