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Neuromyelitis Optica


KEY FACTS

Terminology

  • Neuromyelitis optica (NMO)

  • NMO spectrum disorders

  • Idiopathic inflammatory demyelinating disorder of CNS characterized by severe attacks of optic neuritis and myelitis

Imaging

  • Hyperintense, mildly enlarged optic nerves

  • Expansile, hyperintense cord signal, ≥ 3 segments

  • Long segment optic nerve enhancement

  • Acute cord lesions show patchy enhancement

  • Patchy enhancement with blurred margins (“cloud-like” enhancement) in cerebral lesions

  • “Pencil-thin” ependymal enhancement

Top Differential Diagnoses

  • Multiple sclerosis

    • Radially oriented, well-demarcated perivenular lesions

    • Patchy cord lesions > > long multisegmental

  • Optic neuritis

  • Transverse myelitis

  • Syringomyelia

  • Spinal cord neoplasm

Pathology

  • Serum marker: NMO-IgG , targets water channel aquaporin-4 (AQP4)

  • Seen in 70% of NMO patients, 99% specificity

Clinical Issues

  • Hallmark = severe optic neuropathy, myelopathy

    • May progress to blindness

  • 20% present with brainstem symptoms at disease onset

  • Relapsing course in 90% of patients

  • Anti-AQP4 antibody positivity as prognostic marker

  • Acute exacerbation: IV corticosteroids, immunosuppressives

Axial T1WI C+ FS MR shows a markedly enhancing prechiasmatic right optic nerve and chiasm
, consistent with acute optic neuritis.

Sagittal T2 PD FSE MR in the same patient shows a long segment of cord enlargement with hyperintensity. Ill-defined enhancement was also present in the cervical cord in this patient with myelopathy and vision loss. Patients with neuromyelitis optica (NMO) have a worse prognosis with more severe disability than multiple sclerosis, despite lack of brain involvement.

Axial FLAIR MR in a patient with NMO spectrum disorder (NMOSD) shows characteristic periependymal lesions surrounding the 3rd ventricle, involving the thalamus
and hypothalamus
.

Axial T1+C MR in the same patient shows subtle rim enhancement in the lesion in the right thalamus
. Brain lesions in NMO/NMOSD are typically localized in the periependymal regions where aquaporin-4 is highly expressed.

TERMINOLOGY

Abbreviations

  • Neuromyelitis optica (NMO)

  • Neuromyelitis optica spectrum disorders (NMOSD)

Synonyms

  • Devic syndrome

Definitions

  • Idiopathic inflammatory demyelinating disorder of CNS characterized by severe attacks of optic neuritis and myelitis

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