Secondary nummular headache: Are they more common than we thought?

Objective: To provide a detailed description of symptomatic nummular headache (NH) and to compare them with primary cases in a large series.

Background: While most published cases of NH are primary headache, some 'secondary' cases have been reported since its initial description. It remains uncertain why identical clinical presentations can result from primary and 'secondary' etiologies. Thanks to the possibility of offering specific treatments for symptomatic NH, it is crucial to be able to distinguish between them effectively.

Methods: This monocentric retrospective study included a cohort of patients diagnosed with NH according to the International Classification of Headache Disorders, Second (ICHD-2) and Third Editions (ICHD-3), and the Pareja et al. first description, over a 20-year period (2002 to 2022). Established ICHD-3 diagnoses were used for each symptomatic case. Causality was attributed if (i) headache had developed in close temporal relation to other symptoms and/or clinical signs, or had led to its diagnosis, and (ii) either the headache had significantly worsened in parallel with other symptoms or clinical or radiological signs of worsening of the underlying disease, or the headache had resolved after treatment of the presumed causative disorder. Symptomatic NH were divided into two groups: "definite" or "probable." A comparison between the "primary" and "secondary" groups is presented.

Results: A total of 131 patients (88, 67.2% females) were included in the study. The median (interquartile range) age at onset of symptoms was 52 (36-63.2) years. In all, 34 patients (25.9%) were diagnosed as symptomatic NH (nine post-traumatic, seven attributed to a disorder of the cranial bones, six due to intracranial neoplasia, five attributed to arachnoid cysts, three attributed to vascular malformations, two due to cutaneous disturbances, and two attributed to hypertension). Eight patients were classified as "definite symptomatic NH" and 26 as "probable symptomatic NH." Neuroimaging was performed in all cases. Any previous headache (52.9% vs. 29.9%; p = 0.016), a remote head trauma (26.5% vs. 9.3%; p = 0.015), and a longer disease duration (18 vs. 12 months; p = 0.036) were more likely in patients with symptomatic NH. Preventive treatment was more effective (achieved >50% reduction in monthly headache days) in patients with symptomatic NH (72.2% vs. 30.3%; p = 0.002) due to a cause-specific treatment.

Conclusion: Symptomatic NH are frequent. The presence of any previous headache or remote head trauma may suggest a diagnosis of symptomatic NH; however, as certain NH might be an early symptom of intracranial mass lesions, neuroimaging is necessary. Finding the cause of NH is essential to offer the most effective targeted treatment.