Neuromyelitis optica and multiple sclerosis are two distinct conditions that require different treatments. Distinguishing between the two is crucial for people to get the proper treatment and care.

Neuromyelitis optica (NMO) and multiple sclerosis (MS) both affect parts of the central nervous system. For several years, experts believed that NMO was a form of MS. However, as researchers discovered more about the two conditions, they realized that they are distinct from one another.

Although NMO and MS often present with similar symptoms, it is important to distinguish between the two. Many treatments are suitable for both conditions, but some of the treatments for MS might make NMO worse. Therefore, it is essential to get an accurate diagnosis.

This article looks at the similarities and differences between NMO and MS and explains the treatment options.

NMO is a condition that affects the spinal cord and optic nerve. A doctor may also refer to it as NMO Spectrum Disorder (NMOSD) or Devic’s disease.

It is an autoimmune disorder in which a person’s white blood cells and antibodies attack the optic nerve and spinal cord. This can lead to symptoms that include:

  • swelling and pain in the eyes
  • changes in vision
  • decreased sensation
  • weakness or paralysis in the arms or legs
  • issues with bladder and bowel function

About 4,000 people in the United States are living with NMO. It can affect anyone but is more prevalent among non-Caucasian people.

Multiple sclerosis (MS) is a disease that also affects the central nervous system. Although the exact cause is unknown, scientists believe that something triggers the immune system to attack the myelin sheath, which is a protective barrier around the nerves of the brain, spinal cord, and optic nerve.

When it occurs, it can cause unpredictable symptoms throughout the body. The symptoms can include:

  • numbness and tingling
  • blurry vision
  • mood changes
  • memory issues
  • pain
  • fatigue
  • weakness, usually only on one side of the body

Both MS and NMO are autoimmune disorders. This means that in both cases, a person’s immune system mistakes a healthy part of their body as a threat and attacks it.

They can also cause similar symptoms. In fact, when a person first develops NMO, doctors may mistake the condition for MS.

Although these conditions can affect anyone, they both occur more frequently in females than males. More than 80% of people with NMO and about 74% of those with MS are female. This suggests that sex hormones may play a role in both conditions.

Despite the two conditions sharing some similarities, they are distinct conditions and have several differences.

Average age of onset

The age of onset differs between the two conditions. Although both can appear at any age, an NMO diagnosis is most likely between the ages of 40 and 50 years, whereas MS typically starts between the ages of 20 and 50 years.

Where the immune system attacks

Both conditions involve the immune system attacking the central nervous system, but there are differences in where it attacks.

In more than 70% of NMO cases, the immune system develops specific antibodies — the NMO-IgG or anti-AQP4 antibody — to attack AQP4 on the surface of support cells known as astrocytes. These cells help support the spinal cord, brain, and optic nerves. Damage to the astrocytes is what ends up causing the symptoms.

In MS, there are no specific antibody tests that doctors can use to diagnose the disease.

In some cases, NMO may also affect the myelin sheath. In MS, immune cells attack the myelin, which leads to the symptoms of MS.

In NMO, the immune system only attacks the spinal cord and brain throughout the duration of the disease. In contrast, MS can affect the brain, spinal cord, and optic nerve. The spinal lesions in NMO tend to be larger and located more centrally in the spine, while those in MS tend to be smaller and located near the outer portions of the spine. However, there can be exceptions.

Severity of attacks and disease progression

Another key difference is the severity of the attacks associated with MS and NMO and how they work. People with NMO have a higher likelihood of more severe attacks than those living with MS.

Doctors define MS as progressive but not NMO. In those with NMO, the cumulative decline develops during attacks, not in between them. Conversely, a person with MS can experience progression even without a true attack, resulting in additional disabilities or symptoms. However, the disease does not always progress, and it may result in only mild flares that do not cause additional disabilities.

In NMO, each acute attack can cause debilitating symptoms with irreversible damage. This makes preventing NMO attacks an important part of treatment.


Both MS and NMO can cause fatigue, but they do so in different ways.

Researchers are learning that in MS, fatigue may be either primary or secondary. Primary means that it occurs directly because of MS, whereas secondary means that it is related to another factor.

In NMO, fatigue will be secondary and related to living with the symptoms.

Appropriate treatments for MS and NMO are important for both conditions.

An incorrect diagnosis of MS can be damaging to a person living with NMO. According to a 2016 study, interferon (IFN)-β, which is effective in treating MS, may exacerbate NMO symptoms. In addition, newer therapies called fingolimod (Gilenya) and natalizumab (Tysabri) can both exacerbate NMO.

Instead, doctors may treat NMO with eculizumab (Soliris), inebilizumab-cdon (Uplinza), and satralizumab-mwge (Enspryng) when a person has anti-AQP4 antibodies.

Some of the disease-modifying treatments that the Food and Drug Administration (FDA) has approved for MS are not approved treatments for NMO. Likewise, the FDA has approved some disease-modifying treatments for NMO but not for MS.

While each condition has its own specific types of treatments, certain treatment options can work for both MS and NMO.

Treatments that work for both conditions include options that help prevent the progression of the disease, manage flares, and relieve symptoms.

For acute attacks in both conditions, a doctor may use IV corticosteroids, such as methylprednisolone (Medrol). For long-term therapy, they may recommend immunosuppressant medications for both MS and NMO.

Possible reasons for misdiagnosis

It is not always possible to distinguish between NMO and MS. It is easy to mistake these conditions for each other, especially early in the course of the disease. This is because they have similar symptoms, physical exam findings, and imaging test results.

Many people might carry a diagnosis of “MS or NMO” until certain symptoms or antibodies develop that more definitively point to one or the other.

A doctor can order a blood test to check for the presence of anti-AQP4 antibodies, which are present in more than 70% of all NMO cases but not in MS. However, a person with NMO who does not have this antibody is potentially at risk of misdiagnosis with MS.

A doctor should order several tests and review each person thoroughly to help ensure that they provide the correct diagnosis for a person presenting with symptoms that could be due to MS or NMO.

It may be challenging to live with the ambiguity of not having a clearly defined diagnosis. However, after the initial stage of uncertainty, there will be more clarity, and with a targeted treatment, the outlook will be more positive.

MS and NMO both involve the immune system and can cause similar symptoms. However, there are distinct differences in the part of the body that the immune system attacks and in the treatments for the two conditions.

The diagnosis for either condition should involve a thorough exam and several medical tests, including blood tests, to determine the underlying cause of a person’s symptoms.