How Neuromyelitis Optica Spectrum Disorder Is Diagnosed

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Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune, inflammatory disorder of the central nervous system (CNS), which includes the brain and spinal column. NMOSD also involves the optic nerves. Diagnosing NMOSD involves a physical and neurological examination, blood tests looking for specific autoantibodies, a stimuli response test, and imaging. It must be differentiated from other conditions, such as multiple sclerosis (MS), which may have similar symptoms.

Physical Examination

Your health care provider will take a detailed patient history and do a thorough evaluation to rule out other causes of symptoms similar to those of MNOSD. A complete physical evaluation will be done to observe for signs of NMOSD.

A neurological exam will be performed, evaluating movement, muscle strength, coordination, and sensation, assessing memory and thinking abilities (called cognitive functions) and vision as well as speech.

Your history can help distinguish the symptom pattern seen in the two types of NMOSD. Historically, the condition was known as Devic’s disease. When the condition was first discovered in the late 1800s, it was thought that it was a monophasic disorder featuring a single attack on the spinal cord (transverse myelitis) and optic nerve inflammation (optic neuritis). But, in the 20th century, researchers realized that more commonly, NMOSD was a recurring disorder with flare-ups that occur months or even years apart. 

Two Types of NMOSD

There are two types of NMOSD that have been identified. These include:

  1. The relapsing form of NMOSD involves flare-ups that occur with periods of recovery between episodes.
  2. The monophasic form of NMOSD has a single episode that can last approximately 30 to 60 days, with no subsequent flare-ups.

Autoimmune disorders are those that occur when the immune system mistakenly attacks healthy organs and tissues. In the case of NMOSD, the healthy tissues that get attacked are the nerves in the CNS. The result is inflammation of the nerves and damage that leads to severe symptoms such as visual problems, blindness, muscle weakness or paralysis, and more.

Labs and Tests

Your health care provider may perform may different tests to diagnose NMOSD, these include:

Blood tests: A blood test may be performed to check for an autoantibody, which is an immune protein produced by your white blood cells that mistakenly targets your own tissues or organs. The specific autoantibody that is linked with NMOS, is called aquaporin-4 or AQP4. AQP4 is not present in all people who have NMOSD; but it is the primary clinically approved biomarker for NMOSD.

A biomarker is a measurable substance whose presence may strongly indicate a disease. The AQP4 autoantibody helps to differentiate between those who have symptoms caused by NMOSD and others who have multiple sclerosis.

The stimuli response test (sometimes called an evoked response test): This test measures how well your brain is responding visually and how the brain responds to sound and touch. The test is performed after attaching electrodes (small wires) to the scalp, ear lobes, back (and other areas). These electrodes record the brain’s response to stimuli and enable the health care provider to locate damaged areas and lesions of the optic nerve, spinal cord or brain.

A lumbar puncture test (spinal tap): This test involves removal of a very small amount of spinal fluid to test for proteins, immune cells, and antibodies. The test is performed by inserting a needle into the back and aspirating a small amount of spinal fluid to send to the lab for testing. A markedly increased level of white blood cells may show up in the spinal fluid during an NMOSD episode. This test may be performed to assist the health care provider in differentiating between NMOSD and multiple sclerosis.

Imaging

Imaging commonly performed to diagnose NMOSD may include magnetic resonance imaging (MRI) which utilizes radio waves, along with very strong magnets to produce a detailed image of specific areas that are commonly affected by NMOSD. An MRI may reveal lesions or damage—common symptoms of NMOSD— to the optic nerves, spinal cord, or brain.

Differential Diagnoses

When it comes to a differential diagnosis (ruling out other diseases with similar signs and symptoms), NMOSD can be quite a challenge to diagnose. NMOSD may manifest with very similar signs and symptoms that are common in other disorders, such as:

Ruling out Multiple Sclerosis

When the health care provider performs a diagnostic assessment for a person with symptoms of NMOSD, doing a workup to rule out multiple sclerosis may be a key part of the evaluation. The process may include various tests as well as differentiating between signs and symptoms. Differentiating between NMOSD and MS may be very challenging for the diagnosing physician. But, modern medical science has been able to show that some differences between the two conditions exist, including:

  • Symptoms of NMOSD are usually much more severe than those of MS.
  • MRI imaging tests that show signs of transverse myelitis (long spinal cord lesions that involve three or more vertebral segments of the spinal column) provide strong evidence that a person has NMOSD and not MS (but there are exceptions to this rule of thumb).
  • The brain scan imaging test results are usually normal for those with NMOSD (but not for people with MS).
  • A biomarker called oligoclonal bands is commonly found in those with MS, but not in people with NMOSD.
  • An antibody named the MOG-IgG antibody is found in a subset of people who tested negative for aquaporin-4 (AQP4-IgG). The MOG-IgG antibody is thought to be specific for NMOSD and other inflammatory demyelinating disorders (such as neuromyelitis and acute disseminating encephalomyelitis). But, according to a 2016 study, the MOG-IgG antibody is rarely seen in people with MS.

A Word From Verywell

Going through the process of getting a diagnosis for a severely debilitating disorder, such as NMOSD (or any other demyelinating inflammatory disease), may be a life-changing scenario for many people. Because of this, it’s vital that you get the most up-to-date, accurate information to help you navigate your way through this complex medical ordeal. By becoming informed about the diagnostic process, you will be more prepared to handle some of the stressors you will face, enabling you to make health care decisions. Keep in mind that being open to accepting as much support as possible (including attending local and/or online support groups) and tackling issues a day at a time is highly recommended.

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