Tumor-like Neuromyelitis Optica

Clinical History

An 18-year-old previously healthy girl presents with progressively worsening tetra-paresis over the course of 8 days. There was no history of trauma or infectious parameters, or history of prodromal disease.

Imaging Findings

After neurological evaluation and suspecting a spinal lesion, an MRI was performed. It showed a longitudinally extensive (>3 vertebral bodies) expanding lesion of the medulla and cervical spinal cord, extending to the C6-C7 level (Figure 1). It was T2 hyper-intense (Fig.1a, c), iso to hypo-intense on T1 (Fig.1b), with patchy, irregular enhancement (Fig.1d). There were some cystic lesions in the affected cord, probably corresponding to the entrapment of the ependymal canal.
Given the imaging characteristics and lack of infectious parameters corticosteroids were initiated with clinical and imagiological improvement, as shown in MRI at 3 weeks (Figure 2) and 6 months (Figure 3) of follow up.
Anti-AQP4 antibodies proved positive during aetiological investigation.

Discussion

Neuromyelitis optica (NMO) is an inflammatory demyelinating disorder of the CNS. Once considered a subtype of multiple sclerosis (MS), it has a discrete pathogenesis in which anti-aquaporin 4 (AQP4) antibodies play a critical role [1]. It can be monophasic, but is more often relapsing [2, 4]. It is classically characterized by acute visual loss and/or transverse myelitis [4]. Recent diagnostic criteria for NMO depend on a combination of presence or absence of AQP4-IgG, core clinical characteristics, and exclusion of alternative diagnoses (discussed in detail in reference [6]). MRI plays a particularly important role in AQP4-negative patients.

MRI is the modality of choice and may show spinal, optic pathway and brain lesions. Longitudinally extensive transverse myelitis (≥3 vertebral segments), is the hallmark of NMO. Spinal lesions are T2 hyperintense, may expand the cord, patchily enhance, and preferentially affect the central gray matter [1, 5]. Optic pathway lesions are indistinguishable from other causes of neuritis on MRI, with T2 hyperintensity and gadolinium enhancement, but bilateral and chiasmal involvement should raise the possibility of NMO [1, 3, 5]. Brain lesions can be found in up to 90% of patients [1, 2, 5]. Nonspecific small (<3 mm) T2 hyperintense lesions in the deep or, less commonly, subcortical white matter are the most common finding [1, 3, 5]. Typical lesions (following distribution of AQP4) involve the periependymal areas of the third ventricle, cerebral aqueduct, and fourth ventricle. Involvement of the dorsal brainstem, including the area postrema, is one of the most specific brain abnormalities [5]. Lesions can be MS-like in about 10% of patients, but NMO lesions tend to extend along the walls of the lateral ventricles in close association with the ependymal lining [1] and the cerebral cortex is typically spared, making double inversion recovery sequences helpful in distinguishing NMO from MS in difficult clinical cases [1]. Enhancement is uncommon (<30%)[5]; incomplete ring enhancement, common in acute MS lesions, is not a feature of NMO [1].

Treatment with immunosuppression, should be promptly initiated [3]. Differentiation from MS is critical, as some MS therapies can exacerbate NMO symptoms [5]. Rarely, there can be complete clinical recovery, [4] but prognosis is generally poor, with most patients sustaining permanent neurological deficits [1, 4].

Teaching Points
- NMO may present with a longitudinally extensive transverse myelitis.
- In rare instances it may be mistaken for a tumoral lesion
- Diagnosis is important as treatment is different from other entities and essential to prevent permanent neurological deficits.

Differential Diagnosis List

Final Diagnosis

Neuromyelitis optica

URL:	https://www.eurorad.org/case/13383
DOI:	10.1594/EURORAD/CASE.13383
ISSN:	1563-4086