Abstract
Nummular headache (NH) is a primary headache adopting the form of local pain in a circumscribed area of < 7 cm in diameter in the tuber parietale, albeit it may also be located in other areas of the head. Although it is chronic, it is commonly associated with exacerbations and short periods of remission. Here we report four cases. Two of them could not be considered primary: in one the pain was related to an underlying, pointed and benign lesion disclosed only by magnetic resonance imaging (case 1); the second one had persistent NH days after trans-sphenoidal surgery for a pituitary adenoma, similar to a postcraniotomy headache (case 2). The two final patients suffered from typical forms of primary NH, one associated with migraine without aura, the other with chronic tension-type headache. The response to painrelated treatments and to preventive drugs was poor in the symptomatic as well as in the primary cases. The mechanisms are not clear, and peripheral (case 1) and also central pathways (case 2) could be involved. In the end, secondary forms of NH might coexist with classical primary NH. Particular attention should be paid to tiny skull lesions and to key events preceding the pain.
Nummular headache (NH) was described in 2002, with a series of 13 cases affected by a distinctive head pain (1). It was included in the appendix of the International Classification of Headache Disorders (ICHD)-II in 2004 (2) as a form of primary headache. Pain is mild to moderate, circumscribed to a small round area (< 7 cm in diameter), in the tuber parietale. It is chronic, although spontaneous remissions lasting weeks and acute lancinating exacerbations with a duration of up to 2 h are common. Finally, another criterion requires that structural or systemic abnormalities are to be ruled out by performing laboratory testing and imaging studies. In this sense, it is considered a primary headache, in the original series as well as in later ones (3–7).
In our experience, however, symptomatic cases can be diagnosed if careful attention is paid to underlying cranial lesions, and also to temporal key events in the clinical data. In fact, we provide two cases of typical primary forms, in addition to two others that fulfil the required criteria, except for the presence of a cranial wall lesion in one, and pain having a close temporal relationship with brain tumour surgery in the other. Hereafter, these two cases should be considered secondary forms of NH.
Case reports
Case 1
A 67-year-old man had suffered from local head pain for the past 2 years. It was localized in his left posterior parietal area, in a well-demarcated, rounded zone, 5 cm in diameter. It was mild, continuous, pressure-like and well-tolerated. Nevertheless, exacerbations had appeared during the last 6 months, becoming progressively more frequent and severe. They were spontaneous, but also evoked by combing or touching the area, and lasted between a few seconds and a few minutes. At no time was the pain accompanied by nausea, vomiting, photophobia, phonophobia, red eye, tearing or nasal discharge. There was neither remarkable clinical antecedent nor regular drug intake before the present disorder.
Local inspection and careful palpation of the sensitive area were normal. Fundoscopic examination was also normal, such as frontal, temporal and occipital pulses, which were felt on both sides.
Cranial computed tomography (CT) was considered normal. Magnetic resonance imaging (MRI) disclosed a protruding lesion, about 1 cm long, just beneath the painful area. It was specula shaped, ending in a point, with the bone layer preserved (Fig. 1). A bone scan was normal, with no local enhancing. Laboratory tests included routine blood work, erythrocyte sedimentation rate, standard biochemical determinations, proteinogram, thyroid function, antinuclear antibodies, rheumatoid factor, prostate-specific antigen and urine analysis, with no pathological findings.
Case 1. Axial computed tomography (CT) and magnetic resonance imaging (MRI). CT was considered normal. T2-weighted MRI shows a left parietal point-shaped lesion, protruding outwards from the skull, with preserved bone.
Symptomatic treatment was tried with metamizole, indomethacin and non-steroidal anti-inflammatory drugs (NSAIDs), with no relief. Local infiltration with lidocain partially improved the local discharges of exacerbations. Preventive therapies with amitriptyline, gabapentin and oxcarbazepine were unsuccessful.
Case 2
A 72-year-old woman suffered from arterial hypertension (tiazides), diabetes mellitus (metformin) and osteoarthritis. Acromegaly and a pituitary adenoma had been diagnosed 18 years earlier. The tumour was successfully removed by a trans-sphenoidal approach. Her postoperative period was not complicated. However, it was remarkable that after a few days following surgery, local pain in the vertex emerged. It was mild to moderate, affecting an oval area 4 cm in diameter, and never changed in size or localization. During that period, the patient had 2–8-week periods of total or partial remission. She had no clear exacerbations, and aura, autonomic symptoms and vegetative local signs were absent. No tenderness, pressure-evoked pain or local skin changes were found. Optic perimetry and fundoscopic examinations were normal.
Cranial MRI revealed an empty sella, with no visible tumour and with preserved optic chiasm, bone and aerial structures around the sella (Fig. 2). The same laboratory procedures as in case 1 were performed and were likewise insignificant. Tests for hypophyseal function were also within normal range.
Case 2. Sagittal magnetic resonance imaging. Eighteen years after a trans-sphenoidal approach for a pituitary adenoma, an empty sella is visible. Optic chiasm and other surrounding structures are normal.
She never abused analgesics. There was no response to indomethacin, NSAIDs, amitriptyline, gabapentin or valproic. Nevertheless, the patient was actually relieved when bad prognosis disorders were excluded.
Case 3
A 50-year-old woman had been affected by migraine without aura since her teens. This pain had recently subsided, when she entered menopause. From her 30s she had had a different pain, circumscribed to the right parietal area, to a 4 cm diameter area. This pain was clearly segregated from migraine, as much in clinical characteristics as in response to treatment. In this sense, during the periods of frequent episodes of migraine she was successfully treated with β-blockers, although the local pain persisted unchanged. It was mild, continuous, with periods of exacerbations lasting hours; nausea, vomiting, increase with physical efforts or photophobia were distinctly absent. No response was observed, albeit NSAIDs or triptans relieved migraine. Specific trials with gabapentin and valproic had no effect. The patient suffered from arterial hypertension, low salt diet controlled, and was a former smoker.
Physical examination, with particular attention to inspection and palpation of the local area, was normal; no touching-evoked pain and no trigger point were found. Brain CT and routine blood work were normal.
Case 4
A 37-year-old woman had been followed for chronic tension headache, dating from 20 years earlier. She had never abused analgesics. Amitriptyline, 25–75 mg/day, benefited her tension headache during the more severe periods. In addition, over the last 1.5 years she had been suffering from a distinct pain, localized precisely in an area of 2.5 cm diameter in the left posterior part of her head. It was continuous, throbbing, and of moderate intensity. She never experienced remission periods, although pain intensity waxed for periods of days; during these periods it became severe and lancinating. At no time did she experience photophobia, nausea, vomiting, red eye or tearing. Tenderness of the scalp, sensitive to combing or gentle touching, was present during peaks of the exacerbation periods. Otherwise, physical and neurological examinations were normal and she had no relevant medical background. Blood tests, EEG and cranial CT were normal.
During exacerbation periods she was treated in the hospital emergency department. Intravenous metamizole, indomethacin, oral NSAIDs, triptans and oxygen were tried, with very little relief. Preventive therapy included gabapentin, carbamazepine and topiramate, but she showed no response.
Discussion
The present cases fulfil the criteria for a diagnosis of NH (2). This disorder has been rarely reported. Pareja et al. have described 27 cases in two reports (1, 3). Since then, publications have been sparse, with six more cases in series comprising from three to just one case (4–7). All were considered primary forms. As such, it was mandatory to exclude structural lesions. In the original series, brain CT, MRI or cranial X-rays were used (1), whereas plain X-rays and CT scans were routine in the second broad series (3). Thereafter, neuroimaging procedures were different, with MRI not included for many patients. With such procedures, a lesion such as that of our first patient could have been overlooked. This patient represents a symptomatic or secondary form, which could be more frequent than supposed. Although the exact nature of this lesion is uncertain, it was present in many MRI slices. Consequently, artefact can be ruled out. Cranial lesions such as metastasis, osteomyelitis, Paget's disease and multiple myeloma are a common cause of ‘local tension-type headache’, but also seem unlikely.
Regarding the second case, it is worth noting a close temporal relationship with trans-sphenoidal surgery for pituitary adenoma. In this sense, it could be considered a postcraniotomy headache. This headache is usually a ‘site of injury’ or tension-type headache (8), which is particularly frequent after surgery for vestibular schwannomas. Its mechanism is in dispute, although for our case we postulate a referred pain. It is a localized pain felt at a distance from the stimulated pain-sensitive structures, probably meningeal tissue surrounding the sphenoidal area. Thus, we could explain the pain in the vertex as a typical referral point for the dura mater of this area (9).
Cranial trauma, usually mild, is not uncommon in the series of NH: five of 27 cases from Pareja (1, 3) and one of three in the third largest one (4). Trauma was always mild, and in some patients was clearly related in place and time to pain. Moreover, areas sensitive to touching and local tenderness lead to a hypothetical peripheral origin of the pain, probably compression of a terminal branch of a sensitive nerve or even a neuroma of nerve endings. According to this hypothesis, response to drugs that usually work in neuropathic pain, such as gabapentin, carbamazepine or oxcarbacepine, can be envisaged. This has been described in two former cases (7, 8). None of our cases had a background of traumatic events, although local sensitivity to touching was present in two. All were refractory to one or more of these drugs, which concurs with the larger series reports (1, 3, 4). It was also remarkable that local infiltration with lidocain has been proposed as an alternative therapy to prevent pain coming from local nerve irritation. The results were frustrating in every case were it was tested. Our first case, however, showed a partial response, because exacerbations were alleviated, which certainly favours a peripheral mechanism of pain for this symptomatic form.
Coexistent primary headaches such as migraine and tension-type headache have been already described (1, 3–5), although they are so common in the population that the association could be merely coincidental. Two of our cases suffered from them: migraine in one and chronic tension headache in the other. The chronic continuous type of NH could be confused with chronic migraine or tension headache, although this headache was not so closely circumscribed to a small area and, in addition, was responsive to specific preventive therapies. Pain of NH remained, although it was mild to moderate except for exacerbations. It was usually well tolerated, and the patients were relieved after malignancies were excluded.
A central mechanism of pain has also been proposed for NH (4). Regarding this point, it is worth stressing our second case. It could be a form of postcraniotomy headache that had not been previously described, adopting the form of NH. Damage to basal and perisellar meningeal tissue probably triggered the pain. This case, and also cases 1 and 3, can be precisely dated back by the patients. In this sense, a form of ‘new daily persistent headache’ has to considered, although the restricted and unchanging area of pain makes this diagnosis unlikely.
Finally, there has been a recent observation of a case of NH secondary to a posterior fossa meningioma (10), in addition to a case of local pain secondary to an abnormality of the extracranial arteries in a patient with Marfan syndrome (11). Our cases 1 and 2 should also be considered symptomatic or secondary forms. Thus, the spectrum of NH is probably wider than initially supposed, with symptomatic cases being common. In this sense, criterion D of the ICHD-II, which states that NH pain ‘is not attributed to any other disorder’ (2), probably needs to be revised.