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Neuromyelitis Optica (NMO) Spectrum Disorders

Increased Sensitivity & Specificity with Aquaporin-4-IgG FACS Live Cell-Binding Assays

September 2016

What Is Neuromyelitis Optica (NMO)?

Neuromyelitis optica (NMO) is an inflammatory, demyelinating disease of the central nervous system. NMO is characterized by severe relapsing attacks of optic neuritis and transverse myelitis.

Unlike the attacks associated with multiple sclerosis (MS), NMO attacks commonly spare the brain in the early stages.

The spectrum of NMO was traditionally restricted to the optic nerves and the spinal cord. However, Mayo Clinic physician Vanda Lennon, M.D., Ph.D., discovered an antibody that targets aquaporin-4, the water channel on astrocytes and is a sensitive and specific biomarker for NMO. Since that discovery, a much broader category called “NMO spectrum disorders” (NMOSD) has evolved.

What Is NMOSD?

NMOSD includes patients who are seropositive for aquaporin-4-IgG but have more diverse neurological manifestations.

 

Neurological Manifestation Frequency in NMOSD
Recurrent Longitudinally Extensive Transverse Myelitis (LETM) 60-80%
Single Occurrence LETM 40%
Recurrent Optic Neuritis 20%
Single Occurrence of Optic Neuritis <5%
Intractable Vomiting <5%
Acute Disseminated Encephalomyelitis (ADEM),
Posterior Reversible Encephalopathy Syndrome (PRES)
<5%
Encephalopathy, Sleep Disorder, SIAD <5%
Hearing Loss <5%
Ataxia, Diplopia <5%

 

Why Test For NMO & NMOSD?

To Differentiate Between NMO and Multiple Sclerosis.

  • Although NMO spectrum disorders have very similar clinical and radiologic characteristics to MS, the diseases are treated very differently.
  • A majority of NMO patients, typically women, are initially misdiagnosed with MS.
  • While NMO is treated by immunosuppressant therapy, MS is treated by immunomodulation therapy, which may worsen NMO.

Because An Early Diagnosis Can Stop The Disability.

  • Unlike MS, the neurological disability caused by NMO spectrum disorders is based on the number of attacks rather than a progressive phase of the illness.
  • Initiating therapy early in the course to eliminate recurrence of attacks will minimize patient disability.
  • If not treated appropriately, within 5 years, 50% of NMO patients lose functional vision in at least 1 eye or are unable to walk.

Which Tests Should I Order?

FACS Live Cell-Binding Assay ELISA Indirect Immunofluorescence
Sensitivity1 >80% 60-65% 50-55%
Specificity >99% 99% >99%

The likelihood of having a false-positive result with ELISA methodology is at least 5X greater when compared with the Mayo Clinic Cell-Binding Assay.

When Should I Order AQP4-IgG Live Cell-Binding Assay?

Nerve or Spinal Cord Involvement

Nerve or Spinal Cord Involvement chart

Symptoms Outside Optic Nerve or Spinal Cord

Definitely Order

  • When any of the symptoms below are present in combination with either a single episode of optic neuritis or short spinal cord lesions

Consider Ordering

  • Area postrema syndrome: episode of otherwise unexplained hiccups or nausea and vomiting
  • Acute brainstem syndrome
  • Symptomatic narcolepsy or acute diencephalic clinical syndrome with NMOSD-typical diencephalic MRI lesions
  • Symptomatic cerebral syndrome with NMOSD-typical brain lesions

References

  1. Waters PJ, et al. Serologic diagnosis of NMO: a multicenter comparison of aquaporin-4-IgG assays. Neurology. 2012 Feb 28;78(9):665-71

A Patient’s Story

A Patient Story, Courtney Engel

Courtney uses her violin to continue her fight against a serious autoimmune disease

Word of the recital had spread and Courtney’s friends and admirers responded enthusiastically. It was her first time on stage as a soloist since she’d suffered a devastating loss of vision after developing neuromyelitis optica (NMO).

Learn more...


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