Abstract
Background: Occipital neuralgia is a well-recognized cause of posterior head and neck pain that may associate mild sensory changes in the cutaneous distribution of the occipital nerves, lacking a recognizable local structural aetiology in most cases. Atypical clinical features or an abnormal neurological examination are alerts for a potential underlying cause of pain, although cases of clinically typical occipital neuralgia as isolated manifestation of lesions of the cervical spinal cord, cervical roots, or occipital nerves have been increasingly reported.
Case reports: We describe two cases (one with typical and another one with atypical clinical features) of occipital neuralgia secondary to paravertebral pyomyositis and vertebral relapse of multiple myeloma in patients with relevant medical history that aroused the possibility of an underlying structural lesion.
Discussion: We discuss the need for cranio-cervical magnetic resonance imaging in all patients with occipital neuralgia, even when typical clinical features are present and neurological examination is completely normal.
Keywords
Introduction
International Headache Society (IHS) classification defines occipital neuralgia (ON) as a paroxysmal jabbing pain in the distribution of the greater or lesser occipital nerves or of the third occipital nerve, sometimes accompanied by diminished sensation or dysaesthesia in the affected area (1). The remaining neurological examination must be completely normal, so any other abnormality is an alert for potentially underlying causes of symptoms. The actual incidence and prevalence of ON is unknown, and its pathophysiology remains unclear although many hypothesis have been argued (2,3). ON is considered idiopathic in most cases, but it may be related to any injury to the C2 or C3 nerve roots or occipital nerves. It is usually attributed to chronic entrapment by the neck and posterior scalp muscles when no obvious cause is found (3). Several cases of upper cervical roots or occipital nerve involvement by recognizable lesions have been described, and cervical spinal cord lesions may cause a neuralgiform pain identical to that of ON (4–24).
We report a series of two patients with symptomatic occipital neuralgia caused by vertebral and paravertebral infiltration.
Case 1
A 63-year-old man with a previous diagnosis of localized tongue squamous-cell carcinoma treated with radiotherapy 6 years earlier and in complete remission was admitted with a 2-day history of persistent fever up to 38.5°C without an evident origin. He was receiving no current treatment. He also reported a 5-day history of a sudden-onset, constant, dull pain in the left lower occipital region of the scalp, together with paresthesia and dysaesthesia on the left retroauricular region. There were no asymptomatic phases. He had paroxysmal exacerbations of shooting pain radiating from suboccipital region to retroauricular region when turning his head leftwards or lying down in bed over his back or left side.
Examination demonstrated mild hypoaesthesia and dysaesthesia in the left lesser occipital nerve territory, and acute sharp pain was triggered by pressure over the nuchal region or over the ipsilateral posterior muscles of the neck. A skin plaque with erythema and oedema, assumed as a possible origin for bacteraemia, was found on his right forearm. The rest of the general and neurological examination was completely normal.
Fat-suppression T2 weighted and gadolinium-enhanced T1 weighted cervical magnetic resonance imaging (MRI) showed focal hyperintensity of the deep left paravertebral muscles reaching epidural space through the C3 foramen, suggestive of oedema caused by a pyomyositis (Figure 1). A combined cervical computed tomography-positron emission tomography (CT-PET) showed no sign of tumour relapse. Nevertheless, fine-needle aspiration of the lesion was attempted, but failed to obtain enough tissue for microscopic analysis. Upper cervical and occipital pain was treated with gabapentin up to 300 mg t.i.d., with significant response. Blood cultures were positive for Streptococcus agalactiae and treatment with intravenous antibiotics was continued for 2 weeks. Further evolution was good, with relief of retroauricular pain and dysaesthesia, and control MRI performed 3 weeks and 2 months later showed progressive resolution of the paravertebral muscles infiltration.
Left: Case 1. Axial gadolinium-enhanced cervical T1 weighted MRI showing contrast enhancement of deep left paravertebral muscles at C3 level. Right: Case 2. Sagittal fat-suppression cervical T2 weighted MRI showing hyperintensity of posterior arch of C2 and vertebral body of C7.
Case 2
A 42-year-old man complained of hypoaesthesia and dysaesthesia of the right hemicranium. He had received a diagnosis of non-secretory multiple myeloma when he was 24 years old. He had been treated with different chemotherapeutic agents and had received two bone marrow transplants in the last 8 years, and minimally symptomatic chemotherapy-related axonal sensory polyneuropathy was diagnosed 1 year ago. He had a recent favourable response to treatment with dexametasone, bortezomib, lenalidomide, and zoledronic acid. He had no other medical history.
The patient had a 20-day history of progressive hypoaesthesia and paraesthesia of the right hemicranium including the frontal region and occasional episodes of paroxysmal stabbing pain radiating from suboccipital region to vertex following the theoretical right greater occipital nerve distribution, with some days of complete relief. Turning his head did not increase sensory abnormalities nor triggered the pain, but the symptoms were spontaneously fluctuating along the day. On examination, decreased tactile sensation, dysaesthesia, and allodynia of greater occipital nerve and more subtle of the frontal trigeminal branch territories were present, without any other sign on physical examination. There were no skin lesions and pain was not triggered by percussion or pressing over the point where the greater occipital nerve crosses midway between the mastoid process and the external occipital protuberance (Arnold's point) (25). Cranial MRI was normal, but a fat-suppression T2 weighted cervical MRI showed hyperintensity of the posterior arch of C2 and of the body of C7 suggestive of myeloma relapse (Figure 1). Treatment with pregabalin 75 mg b.i.d. was started and the pain was almost completely relieved 1 month later.
Discussion
Injury to the second or third cervical nerve roots through different mechanisms may result in ON. The diagnosis of this syndrome is made on clinical grounds, according to diagnostic IHS criteria, but atypical features should warrant further study of the cause of the pain (1,3). The presence of sensory impairment or pain beyond the territory of distribution of the occipital nerves are an alert about the underlying aetiology of ON and may be associated to spinal cord lesions or compression (10). Moreover, any other examination abnormality different from mild sensory changes over the occipital nerves cutaneous innervation territory are not typical of ON (10–13). An abnormal neurological examination is an alert for a possible underlying cause and must alert the clinician about the possibility of a structural lesion in the cervical spine. Therefore, a careful clinical evaluation of the upper cervical spine and posterior fossa structures is mandatory in these patients and clinicians should consider imaging of the head or neck when abnormalities are found on neurological examination (14).
However, several cases of ON with typical clinical features and completely normal neurological examination have been described in the literature, in which cranial and cervical MRI showed recognizable causes for the pain, such as cervical spine or cranio-cervical junction myelitis, vascular compression, cavernous angioma, or tumour (15–22). Case 1 had typical clinical features of ON, but Case 2 showed frontal radiation of sensory disturbances and pain, characteristic that has been previously reported in two cases of bulbocervical cavernoma and was attributed to central connections between the posterior fossa branches of C2 and the tentorial branches of the ophthalmic division of the trigeminal nerve (10,18). First trigeminal division pain and sensory disturbances appearing in Case 2 may be explained by the central connections between the descending spinal tract of the trigeminal nucleus with the injured C2-C3 afferent fibres on second-order neurons in the upper three segments of the spinal cord (26). Therefore, we herein describe one case of atypical ON due to atypical characteristics of pain and abnormal neurological examination, and another patient in whom the past and present medical history was the only clue to make a diagnosis despite typical history of pain and neurological examination features of ON (3).
To our knowledge, infectious or neoplastic vertebral and paravertebral infiltration have not been previously reported as a cause of ON. As in our cases, relevant medical history and concomitant pathological processes should also alert clinicians about the possibility of a structural lesion causing ON. According to the described cases and to the previously reported cases with typical features of ON, probably every patient with new onset ON should undergo cranial and cervical MRI in order to rule out any potentially underlying cause of cervical spinal cord, cervical root or occipital nerve disorder.
Footnotes
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Conflicts of interest
The authors declare that there is no conflict of interest.