Abstract
Case report
A 47-year-old White male presented to the clinic with a 5-year history of headache that was gradually increasing in frequency and severity. He localized the headache to a circular area of 5–6 cm in diameter in the right temporal region of the head, non-radiating, throbbing and burning in nature, always in the exact same area and occasionally accompanied by dizziness and blurred vision. He rated the pain 10/10 on the visual analogue scale when the headache was at its peak. No triggers were reported. The patient had a past medical history significant for diabetes mellitus Type 2, hypertension, coronary artery disease and depression.
The patient's previous work-up and management included temporal artery biopsy and erythrocyte sedimentation rate for temporal arteritis and magnetic resonance imaging of the head, all of which were unremarkable.
For acute exacerbations, the patient had received oral and/or parenteral triptans, dihydroergotamine, non-steroidal anti-inflammatory drugs (NSAIDs), combination analgesics/opiates, oxygen inhalation and intravenous as well as oral steroids. Combination analgesics/opiates and triptans were most effective.
For pain prophylaxis, the patient had been on several therapeutic agents including calcium channel blockers, β-blockers, magnesium oxide, tricyclic antidepressants, selective serotonin reuptake inhibitors, NSAIDs and antiepileptic drugs. Antiepileptic agents included carbamazepine, topiramate, valproic acid, gabapentin, lamotrigine and phenytoin. All the prophylactic agents were tried in adequate doses and duration.
The patient also received several auriculo-temporal and occipital nerve blocks; the nerve blocks were effective, but only for a few days. Auriculo-temporal nerve block with 0.5% bupivicaine was the most effective in relieving pain, but the pain relief never lasted more than a week.
Pain relief from the auriculo-temporal nerve block was diagnostic of neuropathic origin of pain from the distal trigeminal nerves at the temporal region.
On examination, the patient pointed to a circular area of 5–6 cm in diameter in the right temporal area of the head. There were no signs or symptoms of sensory dysfunction in the symptomatic area and no tender pressure points were found. No cutaneous abnormalities were noted on the painful area. No manoeuvre could trigger or bring relief to the pain. Rest of the physical examination was unremarkable. A diagnosis of nummular headache (coin-shaped cephalgia) was made.
The patient was started on an Empi Epix transcutaneous electrical nerve stimulation (TENS) unit (frequency 8–10, intensity 7–10), which provided significant pain relief within the next few hours. He was followed up in the Neurology Clinic 8 weeks later and reported using the TENS unit all day except when taking a shower and having been headache free since beginning use of the TENS unit for his nummular headache.
Discussion
The term nummular headache (NH) was first coined by Pareja and colleagues in 2002 as a distinct primary headache disorder (1). NH has been proposed as a distinct type of headache disorder in the Appendix of the second edition of the International Classification of Headache Disorders (ICHD-II); code A13.7.1 (2).
The following diagnostic criteria have been proposed by the International Headache Society (2): A, mild to moderate head pain fulfilling criteria B and C; B
A slight female preponderance has been reported (2). The current hypothesis regarding the pathophysiology of NH is that it is probably localized terminal branch neuralgia of the trigeminal nerve (2, 3).
The painful area is usually in the parietal or temporal-parietal region. The pain remains localized to the same symptomatic area and does not change in shape or size over time. Patients usually experience exacerbations lasting several seconds or gradually increasing over 10 min to 2 h superimposed on the baseline headache. It has been reported that during and between symptomatic periods the affected area may show variable combinations of hyperaesthesia, dysaesthesia, paraesthesia, tenderness and/or discomfort (2, 3). However, in an article by Fernandez-de-las-Penas C et al. it has ben argued that NH patients have lower tenderness than patients with chronic tension-type headache (CTTH) and do not show increased tenderness when compared with healthy subjects. In addition, tenderness in NH patients was noted to be symmetrical between the symptomatic and non-symptomatic sides. The absence of increased pericranial tenderness was thought to be clinically useful in distinguishing NH from CTTH (4).
In about 38% of patients periods of spontaneous remission have been reported, with recurrent pain in the same area of head after weeks or months (2).
In milder forms of headache patients may respond to paracetamol (3), gabapentin or naproxen (1). However, in cases of moderate to severe pain, which can be persistent or associated with frequent exacerbations, response to treatment is variable, with some case reports suggesting resistance to treatment (5). We report a case where a TENS unit was used, which provided complete relief from the chronic NH. TENS is one of the modalities to treat chronic pain. Several clinical reports have mentioned its use for various types of conditions such as low back pain, myofascial and arthritic pain, sympathetically mediated pain, bladder incontinence, neurogenic pain, visceral pain and postsurgical pain (6–8). However, many of these studies were uncontrolled and often case reports, and there has been ongoing debate regarding the efficacy of TENS compared with placebo in reducing pain. Use of TENS for headaches has so far been limited, with no documented case of NH treatment.
Several hypotheses have been put forward regarding possible mechanisms of action of the TENS unit, including: presynaptic inhibition in the dorsal horn of the spinal cord, endogenous pain control (via endorphins, enkephalins and dynorphins), direct inhibition of an abnormally excited nerve and restoration of afferent input (9, 10).
NH is a distinct type of primary headache disorder which can be difficult to treat. Our case report adds further to the available literature. However, clinical trials corroborating the efficacy of TENS are highly warranted.