Frequently Asked Questions (FAQs) About NMO

What is NMO?

Neuromyelitis optica spectrum disorder (NMO) is a rare inflammatory disease of the central nervous system (eye nerves, spinal cord, and brain). It is sometimes also called neuromyelitis optica or NMO.1

NMO is an autoimmune disease. In autoimmune diseases, the immune system cannot tell the difference between healthy cells and invaders like viruses, fungi, or bacteria. Because it cannot tell the difference, the body begins to attack and damage healthy cells.

NMO is also chronic. This means that it lasts for a long time or never goes away completely. There is no cure for NMO, but there is treatment.1

What's the history of NMO?

Neuromyelitis optica (formerly known as Devic disease) was first described 125 years ago. In 2006, the phrase “spectrum disorder” was added to describe the range of brain involvement and symptoms linked to the disease. In 2015, the International Panel for NMO Diagnosis (IPND) changed the diagnosis guidelines for NMO.2,3

What's the relationship between NMO and multiple sclerosis

NMO was once thought of as a type of multiple sclerosis (MS). We now understand that it is its own condition, but it may share features with MS. Because it is often misdiagnosed as MS, the number of people who have NMO may be much higher than reported.1

Who gets NMO?

NMO affects 1 to 10 per 100,000 people worldwide. Doctors do not know the exact number of people living with NMO. There are between 4,000 and 15,000 people in the United States living with NMO, according to different sources. About 250,000 people have NMO worldwide.1,4

Gender, age, and ethnicity

NMO occurs in all parts of the world. Women are 4 to 5 times more likely to be diagnosed with the relapsing form of NMO, especially those with the antibody that targets aquaporin-4 (AQP4). Most people with NMO have no other family member with the condition. The average age of onset for NMO symptoms is between 40 and 50, but NMO may occur at any age. NMO occurs more commonly in those of Asian and African descent.1,4

Fewer than 5 percent of those with NMO are under the age of 18. Children are more likely to have optic neuritis (inflammation of the nerve bundles in the eye) at the onset of the disease. Children are more likely to have a single NMO attack than adults are.1,5

What is the cause of NMO

Doctors do not know the exact cause of NMO. In NMO, the layer that divides the blood and brain can weaken. This layer is known as the blood-brain barrier.1,6

The blood-brain barrier has several jobs:6

  • Protect the brain from substances in the blood that could injure it (“foreign” substances)
  • Allow some healthy substances to reach the brain
  • Maintain a constant environment for the brain

Antibodies are proteins the immune system makes to kill germs. In autoimmune disease, antibodies can also be harmful. A weakened blood-brain barrier allows AQP4 antibodies (AQP4-IgG) to cause inflammation in the brain.7

AQP4 is found in brain cells called astrocytes and helps control water balance in the brain. The brain, spinal cord, and eye nerve (optic nerve) have AQP4. AQP4 antibodies (AQP4-IgG) damage the protective coating (myelin) of the brain cells and produce other proteins that lead to inflammation.7,8

While many with NMO test positive for AQP4 antibodies (AQP4-IgG), about 1 in 4 do not. This adds to the mystery behind the cause of the disease.8

Antibodies targeting another protein called myelin oligodendrocyte glycoprotein (MOG) can also be present in NMO. They are believed to cause similar optic nerve or spinal cord attacks in MOG antibody (MOG-IgG) NMO. However, symptoms of this condition develop differently and need to be treated differently from those of AQP4 antibody (AQP4-IgG) NMO. Men and women are equally likely to get MOG antibody (MOG-IgG) NMO. Children have this disease more often than they have AQP4 antibody (AQP4-IgG) NMO.7-10

It is possible that MOG antibody (MOG-IgG) NMO and AQP4 antibody (AQP4-IgG) NMO will eventually be considered separate diseases, though this is debated. For now, they are considered subtypes of NMO.9,10

What are NMO patterns

There are 2 patterns of NMO. Doctors treat the disease the same, regardless of pattern. Doctors assume every person has relapsing NMO, even after a single attack.8,11


  • More common in children5
  • About 5 to 10 percent of cases11
  • A single attack8
  • Affects men and women equally8


  • 90 to 95 percent of cases11
  • Much more common in women than in men11
  • Periodic attacks with some time in-between11

What can I expect from the progression from NMO?

People with NMO have “attacks” of the disease. Most of these attacks worsen over days and may last weeks to months. These attacks may include vision loss and paralysis, which may or may not improve over time.8

Untreated relapsing NMO relapses with an unpredictable course. Those who are on treatment may continue to relapse. The amount of time between relapses may be longer in those who are treated. However, this is also highly variable.11

What are the prognosis and life expectancy of NMO

New studies have shown that life expectancy for NMO may be longer in recent years because of advances in treatment. NMO is not a disease that is in itself fatal. Instead, the disease may lead to complications that can cause death. Death from NMO varies widely from person to person and is based on factors such as:11

  • Severity of symptoms
  • Delayed or misdiagnosis
  • Other diseases or conditions
  • Choice of treatment

Who will diagnose me with NMO?

On your path to diagnosis, you will likely see at least 2 different doctors. You may first see your primary doctor, who will refer you to specialists. These may include:12,13

  • Neurologist: This doctor specializes in diagnosing, treating, and managing disorders of the brain and nervous system. Some neurologists specialize in autoimmune disorders of the brain and nervous system.
  • Ophthalmologist: This doctor specializes in eye and vision care and disorders. Ophthalmologists differ from other eye care specialists because they are licensed to practice medicine and perform surgery. Some ophthalmologists specialize in the nerves of the eye. These doctors are called neuro-ophthalmologists.

How will diagnosis occur?

Various exams and tests will be used to help diagnose NMO.

Brain and nerve exams

Your neurologist will check a wide variety of functions during your brain and nerve exam (neurological exam), including:14

  • Muscle movements and strength
  • Coordination
  • Sensation
  • Memory and thinking (cognition)
  • Vision
  • Speech

Blood tests

Your doctor might test your blood for AQP4 antibodies (AQP4-IgG), which helps doctors differentiate NMO from multiple sclerosis (MS) and other brain or nerve conditions. This test helps doctors make an early diagnosis of NMO. Those who first test negative for AQP4 antibodies (AQP4-IgG) are often re-tested later if doctors suspect NMO.14

Antibodies targeting another protein called myelin oligodendrocyte glycoprotein (MOG) can also be present in NMO. They are believed to cause similar optic nerve or spinal cord attacks in MOG (MOG-IgG) antibody NMO. However, symptoms of this condition develop differently and need to be treated differently from those of AQP4 antibody (AQP4-IgG) NMO. Men and women are equally likely to get MOG antibody (MPG-IgG) NMO. Children have this disease more often than they have AQP4 antibody (AQP4-IgG) NMO.15,16

Eye exam

Optic neuritis occurs when inflammation damages the optic nerve. Optic neuritis is common in NMO. Because of this, your eye doctor (ophthalmologist) may be the doctor who diagnoses the condition or can be an important part of your team of doctors.7,17

Imaging (MRI)

Magnetic resonance imaging (MRI) uses magnetic fields to make detailed pictures of your organs. A brain and spine MRI is used to help diagnose NMO. This test creates detailed images of your brain, optic nerves, and spinal cord. Your doctor might be able to see lesions (areas of nerve damage) when diagnosing NMO.14

Spinal tap

Cerebral spinal fluid (CSF) is the watery liquid that surrounds and protects the brain and spinal cord. A lumbar puncture (also called a spinal tap or LP) requires a small amount of CSF to be drawn from the space around the spinal cord with a needle. The needle is inserted into your lower back after numbing drugs are given to the area to decrease discomfort.14

Like blood work, this test might also help your doctor differentiate NMO from MS.14

What is optic neuritis?

The optic nerve is the bundle of nerve fibers acting as the communication cable between your eyes and your brain. Optic neuritis occurs when inflammation damages the optic nerve.18

Symptoms of optic neuritis may include:15,18

  • Sudden eye pain or headache – This is usually made worse with eye movement.
  • Problems with vision or complete loss of vision – This usually occurs in 1 eye but can affect both eyes. It can include partial or complete blindness, problems seeing different colors, blurred or tunnel vision, or poor depth perception.

What is the regular course of symptoms

Generally, NMO symptoms begin suddenly. After the first attack, NMO follows an unpredictable path, and remission can vary. Episodes of optic neuritis or transverse myelitis can last weeks to months, and in some cases can last years. However, these symptoms are usually temporary and resolve fully or partially, most often after a course of treatment. Damage from attacks may accumulate, with symptoms worsening over time depending on how often and how severe the attacks are.15

How will the symptoms develop over time?

The chance of recurrence of disease activity is greater than 90 percent. Attacks in NMO can be devastating. Outcomes vary widely with each person. If the disease is left untreated, early and severe disability is common.19,20

How is NMO treated?

Acute treatments

Acute treatment for NMO is used to decrease symptoms of the disease right when they start. Acute treatment includes high-dose steroids and plasma exchange (also called parapheresis or PLEX).20

Preventative treatments

The goal of preventative treatment is to decrease the number or severity of attacks. An attack can lead to worsening disability, making it critical to prevent them. Until recently, prevention drugs were not available to those with NMO.22

Biologics are drugs made from living cells. These cells can come from parts of the blood, proteins, viruses, or tissue. Components from these cells are isolated and tested for activity against human diseases. This process turns the cells into drugs that can treat conditions like NMO.23

As of early 2021, the U.S. Food and Drug Administration (FDA) has approved 3 biologic drugs for the treatment of those with AQP4 antibody (AQP4-IgG) NMO:24,25

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This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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