Isolated Occipital Neuralgia as a Relapse of Neuromyelitis Optica

PRACTICAL IMPLICATIONS

Consider secondary causes of occipital neuralgia, including cervical demyelination, particularly in those with neuromyelitis optica.

Case

A 34-year-old man with a known history of aquaporin-4 (AQP4) seropositive neuromyelitis optica (NMO) presented with a 3-week history of scalp pain. The pain was located predominantly posteriorly, with lightning-like radiation anteriorly. He experienced pain predominantly on the left side with occasional contralateral pain. It was described as burning and electrical. There was a dull background ache, with superimposed exacerbations, triggered by touch of the scalp, and particularly over the occipital protuberance. There was no history of trauma and no history of previous similar pain. There were no other systemic features. Examination showed cutaneous allodynia, but a general neurologic examination was otherwise normal, including the absence of myelopathy.

Medical history was significant for seropositive NMO. The patient had presented 2 years earlier with an area postrema syndrome associated with confusion and myelopathy. Imaging revealed longitudinally extensive lower thoracic myelitis (LETM), in addition to cerebral demyelinating lesions. AQP4 antibodies were positive. He was treated with corticosteroids, plasma exchange, and rituximab, with full recovery over a period of months and no residual deficits. Repeat imaging showed improvement of lesions. He did not receive continuous immunotherapy, however.

The patient was initially diagnosed with occipital neuralgia and trialed on several neuropathic agents with no effect. He later received an occipital nerve block and botulinum toxin injection, with only minor and transitory effect. Initial imaging performed 1 week after the onset of illness showed no new abnormalities, including in the high cervical cord. However, the patient later developed severe neuropathic itch on the upper body. Given suspicion of a secondary cause of occipital neuralgia, repeat imaging was performed, with extensive myelitis involving the high cervical cord and medulla, in addition to several new cerebral lesions (Figures 1 and 2). The cervical lesion did not show contrast enhancement, although several of the cerebral lesions did. It is possible that the lesion was not seen on initial imaging because of the relatively early time of acquisition or to slow evolution of the lesion itself.

Figure 1. Saggital FLAIR MRI of the Brain and Cervical Cord.

Extensive hyperintensity involving the high cervical cord and medulla is shown. Further lesions are seen in the midbrain and around the fourth ventricle. FLAIR = fluid-attenuated inversion recovery.

Figure 2. Saggital T2 MRI of the Cervical and Thoracic Spinal Cord.

Extensive cervical and medullary hyperintensity is again seen.

The patient was diagnosed with isolated occipital neuralgia secondary to a relapse of NMO, with the high cervical cord lesion being the likely symptomatic lesion. It was likely nonenhancing because it was subacute. He was treated with intravenous methylprednisolone, with complete resolution of pain within 2 days.

Discussion

Occipital neuralgia is a headache disorder defined in the ICHD-3 as paroxysmal shooting or stabbing pain over the posterior scalp, in the distribution of the occipital nerve, associated with dysesthesia and allodynia, and triggered by palpation over the affected nerve. There may also be continuous background pain, although this is atypical. A response to local anesthetic blockade helps confirm the diagnosis.¹ It is typically considered a primary headache disorder, although secondary causes may be present, with trauma, vascular lesions, syphilis, and myelitis described.² The greater and lesser occipital nerve arises predominantly from branches of the C2 and C3 rami and innervates the posterior scalp. Lesions involving the C2/C3 region may, therefore, produce the otherwise typical clinical image.

NMO is an inflammatory disorder characterized by LETM, optic neuritis, and area postrema syndrome, among various other features. The spinal cord and, in particular, cervicomedullary lesions are common.³ There are 3 other reports, with 5 patients, on occipital neuralgia related to cervical myelitis in NMOSD.^4,5 A large series of patients with high cervical myelitis secondary to multiple sclerosis and a variety of other inflammatory disorders showed similar clinical features, including itch in several cases.⁵ As in the patient presented here, there was a prompt and complete response to corticosteroids, despite refractoriness to usual therapy. Interestingly, pruritus, primarily related to cervicomedullary lesions, may be more specific to NMO.⁶

The clinician should therefore consider the possibility of C2/C3 myelitis in cases of occipital neuralgia, particularly in those with atypical features, or a known demyelinating disease. Prompt and complete relief of pain can be achieved with corticosteroid therapy, even in cases refractory to usual treatment of occipital neuralgia.

Appendix. Authors

Study Funding

The authors have not declared a specific grant for this research.

Disclosure

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