Nummular headache

INTRODUCTION — Nummular headache is an uncommon headache syndrome characterized by a small, circumscribed area of focal pain. It may also be called "coin-shaped headache." Nummular headache may occur either as a primary headache or as a secondary headache due to an underlying process. Careful evaluation for underlying causes is important for this headache syndrome.

This topic will review nummular headache. Other headache disorders and cranial neuralgias characterized by focal head pain are discussed separately.

●(See "Primary stabbing headache".)

●(See "Overview of craniofacial pain", section on 'Auricular neuralgias'.)

●(See "Occipital neuralgia".)

PATHOPHYSIOLOGY — The pathophysiology of primary nummular headache is uncertain. One hypothesis is that it may be focal neuralgia of a terminal branch of the trigeminal nerve [1]. However, reports of ineffective local anesthetic nerve block suggest a role for other factors [2]. An autoimmune etiology may contribute to the pathophysiology in some patients. Nummular headache has been associated with migraine, but it is unclear if these conditions are related or coexist independently [3,4]. In one series of 23 patients with nummular headache, there was a high prevalence of serum markers of autoimmunity and autoimmune disorders [5].

EPIDEMIOLOGY — Nummular headache is uncommon, with an estimated incidence of 6.4 per 100,000 [6]. The condition appears to be more common in females than males with a reported sex ratio of 1.6:1 [4]. The mean age of symptom onset is approximately 50 years old, but cases in children have also been reported [7-9].

CLINICAL FEATURES — Nummular headache is characterized by a small, circumscribed area of chronic head pain [10-12]. The pain is usually confined to a single round or elliptical unchanging area 2 to 6 cm in diameter. The pain may be continuous or intermittent and recurrent, although in a large minority of cases, spontaneous remissions lasting weeks to months may occur.

●Character of pain – Pain with nummular headache is generally of mild to moderate intensity and may be throbbing, pressing, or stabbing. Baseline pain may be superimposed by more severe paroxysms of lancinating pain which initially last for seconds but can gradually increase in duration to minutes or hours [6,7,10].

The affected area may be allodynic, paresthetic, or hyperesthetic [12]. Light stimuli such as combing the hair or touching the affected area may trigger exacerbations of pain [6].

●Location of pain – The parietal region is the area of scalp most often affected [11]. While nummular headache is typically unifocal, a few reports have described patients with focal head pain in two separate areas [7,13].

●Focal skin findings – Most patients with nummular headache have no abnormal skin findings on the affected area. However, some patients with chronic symptoms may occasionally be found to have hair loss, skin atrophy, or other trophic changes [4]. The presence of rash or swelling associated with focal head pain should prompt evaluation for secondary causes of symptoms. (See 'Secondary causes' below.)

Nummular headache is not accompanied by nausea, vomiting, light or sound sensitivity, rhinorrhea, lacrimation, conjunctival injection, or focal neurologic symptoms that may be found with other headache disorders.

DIAGNOSIS — The diagnosis of nummular headache should be considered in patients with a focal, well-circumscribed area of continuous or intermittent head pain. Nummular headache is diagnosed in patients whose symptoms fulfill diagnostic criteria when alternative causes have been excluded.

Diagnostic criteria — Diagnostic criteria for nummular headache by the International Classification of Headache Disorders, 3^rd edition (ICHD-3) include all of the following [12]:

●Continuous or intermittent head pain

●Pain is felt exclusively in an area of the scalp, with each of the following four characteristics:

•Sharply contoured

•Fixed in size and shape

•Round or elliptical

•1 to 6 cm in diameter

●Not better accounted for by another ICHD-3 diagnosis

The diagnosis of probable nummular headache is made in patients whose scalp pain meets three of the four characteristics and does not meet diagnostic criteria for other headache disorders.

Evaluation — We suggest clinical and cranial imaging evaluation for all patients with nummular headache to identify an underlying secondary cause to symptoms.

●Physical examination – Clinical examination includes direct inspection of the affected area to identify hair loss, rash, or swelling that may indicate a dermatologic condition or underlying mass lesion. Complete general and neurologic examinations are warranted to assess for systemic signs or neurologic deficits that would suggest an alternative diagnosis.

●Cranial imaging – We suggest magnetic resonance imaging (MRI) of the brain with contrast to evaluate for vascular, neoplastic, and infectious lesions involving subcutaneous, cranial bone, and intracranial regions. Computed tomography (CT) of the headache with contrast may be performed as a less sensitive alternative for patients unable to undergo brain MRI. Secondary causes identified on imaging are typically found in close anatomic proximity to the affected area on the scalp [4].

Ultrasound may also be helpful for selected patients to characterize an abnormal subcutaneous finding identified by physical examination or brain MRI.

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of nummular headache includes both primary and secondary headache syndromes that present with focal head pain.

Other primary headache disorders and cranial neuralgias — Primary (idiopathic) stabbing headache may present with focal areas of head pain but, unlike nummular headache, tends to occur as brief spells lasting seconds to minutes. Additionally, the pain with stabbing headache may be multifocal and variable in location. (See "Primary stabbing headache".)

Patients with cranial pain syndromes such as great auricular, auriculotemporal, or occipital neuralgias may present with continuous focal head pain similar to those with nummular headache. However, pain with these cranial neuralgias is typically present over a wider area of the head, in the territory of the impacted nerve, rather than a circumscribed coin-like area characteristic of nummular headache. (See "Overview of craniofacial pain", section on 'Auricular neuralgias' and "Overview of craniofacial pain", section on 'Occipital neuralgia'.)

Secondary causes — Several underlying conditions may be identified on clinical and imaging evaluation of patients with nummular headache. These conditions may be classified into extracranial, cranial (osseous), or intracranial condition. These conditions are often identified by direct inspection and/or imaging evaluation. They include:

●Extracranial conditions

•Subcutaneous aneurysm [14]

•Scleroderma [15]

•Herpes zoster [16]

●Cranial conditions

•Paget disease [17]

•Osteomyelitis [10]

•Cranial hemangioma [17]

•Craniosynostosis [18]

•Granuloma from Langerhans cell histiocytosis [19]

●Intracranial conditions

•Arachnoid granulation [17]

•Cavernous malformation [17]

•Meningioma [20]

•Intracranial stent [21]

TREATMENT — Symptomatic treatment for patients who present with nummular headache includes oral analgesics or other agents such as gabapentin as well as local therapies such as botulinum toxin injections. Some patients with nummular headache may not seek treatment when symptoms are mild or when episodes are brief and/or infrequent.

Patients with secondary nummular headache may warrant and improve with treatment of the underlying etiology [14,17]. (See 'Secondary causes' above.)

Initial oral therapies — For patients with mild symptoms who desire treatment, we suggest initial treatment with simple analgesics over other oral or local options. For patients with more severe or persistent symptoms and those who do not respond to analgesics, we suggest initial treatment with gabapentin.

Treatment options are based on clinical experience, case series, and individual reports as no therapies have been evaluated or directly compared in randomized trials [4]. In a prospective observational study of 72 patients with nummular headache, analgesic medications were reported to be effective (>50 percent pain reduction) in 72 percent [7]. Among 42 patients who were prescribed a preventive medication, gabapentin was used most frequently and reported to be effective in 84 percent. In another series of 183 patients, a greater than 50 percent reduction in pain was achieved by 44 percent with gabapentin, compared with 39 percent for amitriptyline and 35 percent for lamotrigine [22].

Dosing and options for initial oral treatment include:

●Simple analgesics – Nonsteroidal antiinflammatory medications that may be attempted include ibuprofen (400 to 600 mg every six hours as needed), naproxen (250 to 500 mg every 12 hours as needed), or indomethacin (25 to 50 mg every 8 to 12 hours as needed) [4,23].

●Gabapentin – Several case series of patients with nummular headache have reported partial or complete relief with gabapentin titrated to a daily dose of 900 to 1800 mg [1,24].

●Alternative treatment options – Other oral agents may be attempted for patients who do not tolerate or respond to analgesics or gabapentin and include [4,7,22,25]:

•Lamotrigine

•Amitriptyline

•Pregabalin

•Carbamazepine

For patients with a partial response to initial therapy, another agent from a different class may be added. For patients whose symptoms resolve with oral therapy, we attempt to wean medications typically after three months. Treatment may be resumed if symptoms relapse. Some patients with nummular headache may require treatment for several months or even years. (See 'Prognosis' below.)

Botulinum toxin for refractory symptoms — For patients with symptoms refractory to oral therapies, we suggest botulinum toxin. Small series suggest botulinum toxin injections may be effective for patients with symptoms that do not respond to oral therapy [26]. Dosing is not standardized and may vary by size of the affected area. One series used a regimen of onabotulinumtoxinA 25 units delivered in five divided doses within the affected area and repeated 12 weeks later [27]. In this series of 53 patients with nummular headache, treatment was associated with a reduction in the mean number of headache days per month from 24.5 at baseline to 6.9 between weeks 20 and 24 [27]. The response rate (>50 percent pain reduction) to botulinum toxin injections ranges from 63 to 77 percent [22,27].

Other therapy not recommended — Treatment with local injection of anesthetic agents (eg, lidocaine) have been attempted, but most series suggest this is ineffective for most patients [17,28,29].

PROGNOSIS — Patients with nummular headache have variable courses with some patients reporting resolution of symptoms following initial treatment while others continue long-term treatment for chronic symptoms. For some patients, nummular headache can be refractory to all standard prophylactic and analgesic therapies [28,30].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Migraine and other primary headache disorders".)

SUMMARY AND RECOMMENDATIONS

●Definition and epidemiology – Nummular headache is an uncommon headache syndrome characterized by a small, circumscribed area of focal pain. It may also be called "coin-shaped headache." It may occur either as a primary headache or as a secondary headache due to an underlying process. Nummular headache occurs most often in middle-aged adults and has an estimated incidence of 6.4 per 100,000. (See 'Introduction' above and 'Epidemiology' above.)

●Clinical features – Nummular headache is characterized by a circumscribed area 2 to 6 cm in diameter of chronic, throbbing head pain. The pain is continuous or intermittent and recurrent, although in a large minority of cases, spontaneous remissions lasting weeks to months may occur. The parietal region of the scalp is the most affected region. Light stimuli such as combing the hair or touching the affected area may trigger exacerbations of pain. (See 'Clinical features' above.)

●Diagnosis – The diagnosis of nummular headache should be considered in patients with a focal, well-circumscribed area of continuous or intermittent head pain. Nummular headache is diagnosed in patients whose symptoms fulfill diagnostic criteria when alternative causes have been excluded. (See 'Diagnostic criteria' above.)

●Evaluation – We suggest physical examination and cranial imaging evaluation for all patients with nummular headache to identify an underlying secondary cause to symptoms. (See 'Evaluation' above.)

●Differential diagnosis – The differential diagnosis of nummular headache includes both primary and secondary headache syndromes that present with focal head pain. Underlying subcutaneous, osseous, or intracranial conditions may be identified by examination and/or imaging. (See 'Differential diagnosis' above.)

●Treatment – For patients with mild symptoms who desire treatment, we suggest initial treatment with simple analgesics over other oral or local options (Grade 2C). For patients with more severe or persistent symptoms and those who do not respond to analgesics, we suggest treatment with gabapentin (Grade 2C). Botulinum toxin injections may be effective for patients with symptoms that do not respond to oral therapy. (See 'Treatment' above.)