Abstract
Introduction: Nummular headache is a rare primary headache disorder described by a focal circumscribed area of pain (2–6 cm in diameter). Literature on this disorder is sparse.
Patients and methods: Here, we describe a case series of 16 patients (6 men, 10 women) seen at the Mayo Clinic.
Results: Mean age of onset was 50 years (range, 19–79 years) and mean duration of headache was 7.9 years (range, 0.33–40 years). Location of headache varied and was found to be an average of 3.9 cm in diameter (range, 2–10 cm). Headache was episodic (<15 days/month) in four patients and chronic (>15 days/month) in 12 patients. Attention was paid to therapeutic interventions. Resolution was seen in 38% of patients. Migraine was present in the history of 56% of patients and medication overuse headache was found in 25%.
Conclusions: Our series results support previous findings. In our population, no specific therapy was identified to be effective in more than one patient.
Introduction
Nummular headache was first described by Pareja and his group (1) in 2002 reporting a series of 13 cases. It has since been included in the International Classification of Headache Disorders, 2nd edition (ICHD-2) under the category of cranial neuralgias and central causes of facial pain. The clinical picture of nummular headache describes pain in a small circumscribed area of the head (between 2–6 cm in diameter) in the absence of any lesions (2). Pain is typically mild to moderate but has been reported as severe in nature (2–4). A small number of cases have reported successful treatment with various therapies, although there is no clearly effective standard of treatment (5–10).
Since first characterised, approximately 60 cases have been reported in the English literature. Here, we describe a case series report of 16 patients seen at Mayo Clinic’s Department of Neurology between 2003 and 2007. This is the largest case series reported in the US. Particular attention was paid to pain phenotype and therapeutic interventions.
Patients and methods
Patients diagnosed with ‘nummular headache’, ‘numular headache’, or ‘coin-shaped headache’ were indexed through the Mayo Clinic electronic records for patients. A total of 17 cases were identified from 2003–2007, of whom all were diagnosed by a neurologist or headache neurology sub-specialist. One patient was excluded due to incomplete medical record data. A total of 16 cases were incorporated into the study. They all met ICHD-2 proposed criteria for nummular headache (2). Medical records were reviewed and 13 patients were contacted by telephone for additional information using a phone survey to verify and complete the medical record. Data collected included age, sex, presence of skin changes or trauma, baseline sensory abnormalities, location, size, shape, pain type, therapeutic history, presence of other headache disorders, and outcome. If this information was not documented in the medical records, it was gathered during patient telephone interviews. The presence/absence of any skin changes in the painful area could be confirmed in 13 cases, potential trauma association confirmed in 14 cases, and dysesthesia confirmed in 15 of the total 16 patients. Another patient could not be contacted and information regarding duration and remission were extrapolated from her documented last visit. All other data were confirmed in all 16 patients.
Results
Sixteen patients were included in this series (6 men, 10 women). The mean age at onset was 50 years (range, 19–79 years). No paediatric cases were identified. Mean duration of headache defined as the time until resolution or up until time of interview was 7.9 years including cases that were 14, 16, 21, and 40 years in duration. Post-traumatic nummular headache was identified in one patient and was noted to be temporal beginning immediately after trauma. Mean size of nummular headache circumscribed area was 3.9 cm (range, 2–10 cm) in diameter. Location of the headache was described as parietal in six patients, temporal in four patients, vertex in three patients, frontal in two patients, and occipital in one patient. The shape of the painful area was clearly circular in nine patients and oval in one. The exact shape of the affected area could not be determined in six patients, and was recorded in patient records as ‘diameter’ in four cases, as a cubic inch in one, and as a ‘clearly circumscribed’ area in another. No patient had more than one area of pain.
Nummular headache patient profiles
P, parietal; T, temporal; F, frontal; V, vertex; O, occipital.
Chronic indicates >15 headache days per month.
Episodic indicates <15 headaches days per month.
‘Current’, presence or absence of on-going headache at time of telephone interview.
Duration, number of years until resolution or until last follow-up.
Exact shape could not be determined when recorded as one cubic inch, diameter, or circumscribed.
Discussion
Our findings appear to affirm prior studies (4,12). We did see a clear pattern of a persistent underlying pain, often described as a dull ache with clinical exacerbations of sharp, stabbing, jabbing, or throbbing pain. Similar to previous studies migraine co-morbidity was found in our population (1,11,12). Skin abnormalities were not found in our group of patients (n = 13). However, it is uncertain if skin changes only clearly manifest with chronicity (11). With the exception of one patient who had pain exacerbation when touching the affected area, documented in the medical record and in interview, we did not find evidence of tenderness to palpation as in other studies (13). Patient 1 experienced headache symptoms post-trauma, it is worth noting that this patient also had the largest area of 10 cm in diameter.
No specific therapy was identified to be effective in more than one patient. However, it is noted that very few patients completed a thorough regimen of available therapies with less than a quarter attempting tricyclics or topiramate and no patients attempting valproate. However, 38% did have eventual resolution either with medication or spontaneous resolution. Botulinum toxin type A (BoNTA) was not attempted on any of our patients, but may be an area of further research since it may help in a small subset of patients (5).
It is unclear how common nummular headache may be in a general population and difficult to extrapolate since more mild or moderate cases likely do not instigate a physician referral or are not commonly addressed by non-headache physicians. Our population is likely subject to a selection bias of refractory cases. There is the potential to underestimate therapeutic efficacy in the general population. Limitations were noted in the relatively few cases diagnosed with nummular headache given its relatively recent description. We also had relatively short follow-up, therefore not fully appreciating the natural course of the disorder particularly as to whether or not they improve or worsen with time.