Neuromyelitis Optica Spectrum Disorder (NMOSD)


Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoantibody-mediated inflammatory disease that damages the tissues of the central nervous system. It is mainly characterized by inflammation of long segments of the spinal cord (myelitis), severe optic neuritis, and/or bouts of intractable vomiting and hiccups. Around 75% of patients with NMOSD have autoantibodies against aquaporin-4, a water channel expressed on astrocytes; these cells are required for the survival and function of nerve cells.1

Common symptoms of NMOSD include ocular pain (also called an “eye headache”), varying degrees of vision loss due to optic neuritis, numbness or weakness in the arms or legs due to transverse myelitis, loss of balance, dizziness, abnormal sensations such as pins and needles, and bowel and bladder control problems. The brainstem and brain may be involved in rare cases.2

NMOSD may occur in 2 ways – a monophasic form that occurs in only 10% of patients, in which optic neuritis and myelitis occur simultaneously, and a relapsing form with intermittent optic neuritis and myelitis attacks.3

The symptoms of NMOSD can vary in severity, disability, and duration from person to person. The disease follows an unpredictable course after the initial attack, and the time to remission can vary. Optic neuritis generally occurs suddenly, while transverse myelitis develops over hours or days. The duration between recurring episodes can be months or years. However, these attacks are often temporary and resolve fully or partially after treatment.3

Since optic neuritis and myelitis are also symptoms of multiple sclerosis (MS), it may be difficult to distinguish between NMOSD and MS, particularly in the early stages of the disease. However, NMOSD can be distinguished from MS by greater severity of optic neuritis and myelitis, an absence of oligoclonal bands in the cerebrospinal fluid, and normal brain magnetic resonance imaging (MRI).4

Symptoms of Optic Neuritis 

Optic neuritis is a painful inflammation of the optic nerve and the most common initial symptom of NMOSD. Symptoms of optic neuritis may include rapid onset of ocular pain that is worsened by eye movement, followed by impaired or complete loss of vision unilaterally; in some cases this can occur bilaterally. Other symptoms include reduced visual clarity, light perception, color vision, or depth perception. Prodromal upper respiratory infection may or may not occur prior to NOSD. Around 50% of patients lose their vision within 5 years of symptom onset.2,5

Symptoms of Transverse Myelitis

Transverse myelitis is an inflammation of the spinal cord (usually more than 3 spinal cord segments), which may affect motor, sensory and autonomic functions. Symptoms include pain in the head, neck, or back; tightness in the abdomen, arms, or legs; increased sensitivity to touch, cold, and heat; feelings of numbness, tingling, coldness, itching, and/or burning, often spreading to large parts of the body over a period of minutes, hours, or occasionally days; weakness in the arms or legs ranging from mild to complete paralysis in 1 or multiple limbs; urinary dysfunction (including an urgent need to urinate, difficulty urinating, or urinary incontinence); constipation leading to vomiting, abdominal bloating, pain, and inability to pass stool or gas; bowel incontinence; muscle spasms along with arm or leg pain; and fever in some cases.2,5

Brainstem Involvement Symptoms

In some cases, the brainstem and brain may be involved, such as the area postrema of the medulla, nucleus solitarius, ventrolateral respiratory center, or nucleus ambiguus causing intractable nausea, vomiting, or hiccups. Atypical symptoms include an asymptomatic increase in creatine kinase levels. Involvement of the hypothalamus and temporal lobe may cause hypersomnia and narcolepsy. Galactorrhea and hyperthermia can also occur due to involvement of the hypothalamus.5

References

  1. Huda S, Whittam D, Bhojak M, Chamberlain J, Noonan C, Jacob A. Neuromyelitis optica spectrum disorders. Clin Med (Lond). 2019;19(2):169-176. doi:10.7861/clinmedicine.19-2-169
  2. Neuromyelitis optica (NMO): what you need to know: a guide for patients, their families and caregivers (third edition). Guthy-Jackson Charitable Foundation. Accessed October 25, 2021.
  3. Wingerchuk DM, Hogancamp WF, O’Brien PC, Weinshenker BG. The clinical course of neuromyelitis optica (Devic’s syndrome). Neurology. 1999;53(5):1107-1114. doi:10.1212/wnl.53.5.1107
  4. Neuromyelitis optica spectrum disorder. National Organization for Rare Disorders. Accessed October 25, 2021.
  5. ​​Zarei S, Eggert J, Franqui-Dominguez L, et al. Comprehensive review of neuromyelitis optica and clinical characteristics of neuromyelitis optica patients in Puerto Rico. Surg Neurol Int. 2018;9:242. doi:10.4103/sni.sni_224_18

Reviewed by Harshi Dhingra, MD, on 10/27/2021.

Reviewed by Harshi Dhingra, MD, on 10/27/2021.

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