Nummular Headache Linked to Range of Secondary Causes

A rare coin-shaped headache long viewed as a primary headache disorder frequently has underlying causes, according to new research, and clinicians should refer people who present with it for imaging.

First described in 2002, nummular or coin-shaped headache comprises an intermittent or constant pain limited to a rounded region between 1 and 6 cm in diameter. Classed as a primary headache by the International Classification of Headache Disorders (ICHD-3), it usually occurs in the parietal, or top rear, region of the head.

Despite nummular headache’s classification as a primary disorder, studies have linked some cases of coin-shaped headache to cranial or intracranial lesions. Now, a group of Spanish researchers has revised 20 years’ worth of cases, representing the largest series to date, and found a wide variety of causes, some of which, they say, had not been reported before in connection to this headache type.

For their research, published online on December 3 in Headache, Antonio Sánchez-Soblechero, MD, and colleagues at the University Hospital Gregorio Marañón in Madrid, Spain, looked at clinical and imaging findings from 131 patients (67% women, median age at onset 52) seen from 2002 to 2022 at their center, seeking to identify any differences among primary and secondary or symptomatic coin-shaped headache cases. All patients underwent cranial MRI, CT, or both.

Altogether, 26% of the nummular headaches (n = 34) were found associated with trauma, vascular malformations, cranial bone disorders, neoplasia, arachnoid cysts, hypertension, aneurysm, or skin disorders including, in one case, a psoriasis plaque. Hypertension, aneurysm, and psoriasis were not previously described as causes of this headache, the authors said.

The definition of a nummular headache includes that secondary causes need to be excluded, according to the ICHD-3. The study authors proposed that “definite” secondary cases should meet ICHD-3 diagnostic criteria for nummular headache as well as for secondary headache, while “probable” cases meet all criteria for the former and all but one of the criteria for the latter. In their study, eight patients met the proposed criteria for “definite,” while the rest were deemed “probable” secondary cases.

Headache symptoms remained similar regardless of etiology, Sánchez-Soblechero and colleagues found, but coin-shaped headaches deemed to have secondary etiologies were significantly more likely to be associated with previous headache, remote head trauma, and longer symptom duration. The authors described treatments, including surgical interventions, for cases with secondary causes.

Preventive treatment was more effective in patients with determined causes for their headaches, Sánchez-Soblechero and colleagues found, with 72% seeing their monthly headache days halved, compared with just 30% of patients in whom a cause was not identified.

“The presence of any previous headache or remote head trauma may suggest a diagnosis of symptomatic nummular headache; however, as certain nummular headache might be an early symptom of intracranial mass lesions, neuroimaging is necessary. Finding the cause of nummular headache is essential to offer the most effective targeted treatment,” the investigators wrote in their analysis.

Primary Headache or Secondary?

In an interview, neurologist and headache specialist Nina Riggins, MD, PhD, of VA Palo Alto Health Care in Palo Alto, California, praised the new findings as underscoring the importance of a thorough clinical approach.

“What this study shows is applicable to many primary headache disorders, whether migraine or cluster or nummular,” Riggins said. “Secondary headache can look like all of these headache types.”

Understanding what should be done to rule out secondary causes of headache is key for the correct diagnosis, she said. “In cases of coin-shaped headache, one should do a detailed neurological exam, consider imaging, check blood pressure, do blood work, and consider exams to exclude autoimmune psoriasis and other disorders as appropriate.”

Despite the inherent limits of its retrospective, single-center design, the study by Sánchez-Soblechero and colleagues is “extremely helpful in emphasizing that we should not dismiss [nummular headache] because it’s a little area of 1-6 centimeters,” Riggins said. “We absolutely have to make sure that we have ruled out secondary causes.” And while it would be useful to have evidence from prospective studies of nummular headache, “with such a rare headache, it’s hard. That’s why it’s so precious to have a study like this one, with 131 patients.”

Riggins acknowledged that the study emphasized the challenges of classifying and diagnosing nummular headache. The ICHD, last revised in 2018, “is a living, breathing document,” she said. “The idea is that as we learn more about headache disorders over time, this may mean changing some primary headaches to secondary, but we are clearly not there with this research: Most participants did not have a secondary cause for their coin-shaped headache.”

For now, Riggins said, “I think it’s best to keep classification straightforward for primary and secondary headache. It’s helpful for my day-to-day clinic life to have this neat division in place. But we do have to exclude secondary headache whenever possible in order to say that this is primary headache.”

Sánchez-Soblechero and his co-authors disclosed no financial conflicts of interest related to their findings. Riggins disclosed consulting work for Gerson Lehrman Group, receiving research support from electroCore, Theranica, and Eli Lilly and Company, and serving on advisory boards for Theranica, Teva Pharmaceuticals, Lundbeck, and Amneal Pharmaceuticals.

Jennie Smith is a freelance science writer.