Abstract
Nummular headache is a coin-shaped, chronic cephalalgia usually considered to stem from epicranial tissues. We describe a patient complaining of circumscribed pain in the head as the only symptom of a subtentorial meningioma. This observation underlines the need to revise the concept of circumscribed, referred pains in the head arising from pain-sensitive intracranial structures.
Introduction
Nummular headache (from Latin nummus, meaning coin) is a chronic, mild-to-moderate pain felt in a coin-shaped or elliptical area in the head (1). Pain is normally considered to stem from terminal branches of the trigeminal nerve, although epicranial structural lesions need to be ruled out (2). We report a patient with circumscribed pain in the head as her only symptom of an underlying intracranial mass lesion.
Case report
A 60-year-old woman incidentally reported a left retroauricular discomfort which she had noticed about 1 year earlier while combing her hair, but was mild enough to have not requested medical attention. Other than life-long, infrequent episodes of migraine without aura, she felt generally well. The only neurological abnormality on examination consisted in a small, round-shaped area of tenderness on the scalp, behind the left mastoid, evidenced by mild pressure or gentle touching (Fig. 1a). Brain magnetic resonance imaging revealed a contrast-enhancing, extra-axial mass in the left posterior fossa arising from the tentorium cerebelli with invasion of the left transverse sinus (Fig. 1b). Subtotal tumour resection was performed and pathological examination revealed a meningioma. The pain disappeared shortly following the surgical procedure and the patient remains asymptomatic 2 years later.
Location of pain behind the left ear is shown by shadowed area (a). Magnetic resonance imaging of the head shows a left posterior fossa meningioma attached to the tentorium (b).
Discussion
Nummular headache (NH) resembles focal pain caused by circumscribed lesions in the cranial bones, such as metastases, osteomyelitis and Paget's disease of the bone, tumours in the vicinity of the skull, or even focal abnormalities of the extracranial arteries (3). We report a patient whose only symptom was a circumscribed pain in a single, unilateral area of the head, very much like NH. The painful area, behind her left mastoid, changed neither in shape nor in size with time, mainly consisting in mild local tenderness. However, contrary to normal neuroimaging findings described in NH, our patient harboured a mass lesion in the vicinity of intracranial pain-sensitive structures.
The concept of referred pain, defined as any pain which is felt in a fairly discrete area of the homolateral head at a distance from the stimulation point of pain-sensitive structures within the cranium, is an old one (4, 5). The patient described complained of tenderness and dysaesthesia in a small, round-shaped area behind the ear, homolateral to a meningioma attached to the inferior surface of the tentorium cerebelli and inferior wall of the transverse sinus. Traction and displacement of these pain-sensitive structures supplied by the tenth cranial nerve and smaller branches from the ninth and twelfth cranial nerves presumably explained her headache (6). The pain was relieved with surgical removal of the lesion, supporting the fact that both were related.
Failure to recognize this pattern of headache in intracranial tumours may be explained because most studies have investigated patients in neurosurgical wards, with diseases in a far more advanced stage. Neurologists may also have neglected the concept of referred, focal pain in the head stemming from intracranial structures, a crucial step in early diagnosis of some intracranial mass lesions, as exemplified by our case.
NH has provisionally been considered an epicranial headache, the origin of pain being in both internal and external layers of skull and scalp, including epicranial nerves and arteries (7). However, we wish to emphasize the established concept that circumscribed pain in the head may arise from intracranial pain-sensitive structures. Proper terminology for circumscribed pains on the scalp is controversial (8). The term epicrania has been proposed, implying pains stemming peripherally (9).
We believe NH may be descriptively appropriate, provided primary and secondary forms of the syndrome are assumed, the latter including pains arising from either intracranial or extracranial structures. Our observations lead us to conclude that certain NHs might be early manifestations of intracranial mass lesions and therefore appropriate imaging studies should be performed.