« Nummular headache »: a 5 CHF coin-shaped headache

Nummular headache is the term given to a condition characterized by a continuous or intermittent pain that is felt in a contoured and fixed coin-shaped elliptic area (2-6 cm, usually as a 5 CHF coin) of the scalp, generally on the parietal area. Rarely the disorder could be bifocal or multifocal. Nummular headache is a form of epicranias (group of headaches and neuralgias stemming from epicranial tissues).
The pain is generally moderate but patients can present strong exacerbations or disturbing tingling sensations or also allodynia and hyperpathy by touching or combing the hairs in that region. Rarely patients report this pain after muscular exercise, after Valsalva maneuvers or during menses. Some patients have some association of nummular headache and migraine (however, in these cases the evolution of the two conditions appear quite independent). Patients can rarely present some local scalp changes (for example alopecia). Patients generally fear to have some cerebral disorder and seek consistently for medical advice. Brain MRI or CT-scan are usually demanded to exclude secondary causes and to reassure the patients on the absence of brain anomalies. The reproduction of the patient’s pain by moderate pressure over that coin-shaped region or by stretching the scalp of that area (usually I do with the knuckles of my hand) indicate the local origin of the pain. This area is usually well delimited, and this is an important feature to retain the diagnosis of nummular headache. In the majority of cases, it is not possible to determine any specific cause to the disorder. The pain, for its characteristics, should originate from little nerve branches there.
In exceptional circumstances, patients with nummular headache are diagnosed with meningiomas, arachnoid cysts, craniosynostosis, calcific hematomas of the scalp or other vascular anomalies (aneurysms or other) of the superficial arteries of the scalp. For this reason, during the clinical examination, the examiner should check for vascular abnormal pulsations or bruits over the scalp. In that cases scalp ultrasonography could be a useful investigation. Some patients develop nummular headache after transphenoidal or other meningeal surgery, which could suggest a meningeal or central sensitization mechanism for pain. A central or peripheral trigeminal sensory mechanism is also suggested by the fact that patients with pituitary adenomas might have pain referred to the vertex of the skull. Other authors suggested that the disorder is due to a local diminished threshold for pain even if for unknown reasons. Few patients with nummular headache were found with autoimmune disorders.
Schwartz et al. made a review of 256 cases reported in the scientific literature (http://www.ncbi.nlm.nih.gov/pubmed/23616207).
Treatment with Gabapentin could be helpful but generally is not curative. Other patients responded to amytriptiline, carbamazepine, indometacine or other NSAIDs or even to TENS application. Some patients improve with Botox scalp injections. I propose to try ice bags or cool spray. There are few data on patients who underwent scalp focal resections to treat the disorder.
The scientific literature give few data on the long-term follow-up of this disorder. I think that most patients can have temporary or long term remissions which could be independent from any therapeutic interventions.
Even if I diagnosed this condition for few patients, by examining the literature data, as also indicated by Pareia et al (http://www.ncbi.nlm.nih.gov/pubmed/19810895), I have the feeling that, once that a normal brain MRI excluded other possible primary disorders, in most of these patients, the treatment is seldom necessary and simple reassurance is sufficient.
I think that nummular headache is still a mysterious disorder.