Neuromyelitis optica (NMO) is an inflammatory condition that affects the protective covering of the spinal cord and optic nerves.

Thisarticle explains the types, causes, symptoms, and treatments of NMO. It also looks at how doctors diagnose this condition and the complications that it can cause.

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Doctors may also call this NMO spectrum disorder. Another name for it is Devic’s disease.

NMO is a rare, severe autoimmune disorder in which white blood cells and antibodies damage the optic nerve, spinal cord, and rarely, the brain.

More specifically, they attack myelin, a protective layer that covers the nerves and helps them send signals to and from the brain. This process classifies NMO as a demyelinating disease.

Demyelination temporarily prevents nerves in the spinal cord and the optic nerve from communicating. This causes symptoms such as weakness, decreased vision, and in some cases scarring, which leads to lasting neurological effects.

People with NMO can develop optic neuritis, which causes eye pain and vision loss. They can also develop transverse myelitis (TM), which causes weakness or paralysis in the arms and legs, as well as a loss of bladder and bowel control.

Symptoms of NMO may vary and become more severe after multiple episodes, and confirming the triggers for these episodes requires further research. Resulting nerve damage can cause permanent damage and disability.

NMO affects about 4,000 people in the United States and 250,000 people worldwide. It is significantly more common in women, who experience more than 80% of cases.

It can develop at any age, but doctors typically diagnose it in people aged 40–50 years.

Everyone with NMO experiences at least one episode of inflammation of the optic nerve and spinal cord. There are two types of the condition — relapsing, which is more common, and monophasic, which is rare.

Monophasic NMO

This, less common, form of NMO causes a single episode that lasts for several months.

Relapsing NMO

This type is significantly more common — 90% of people with the condition have more than one episode.

An initial, short episode of inflammation in one or both optic nerves and the spinal cord is followed by more episodes over several years.

Symptoms may include:

  • weakness in the arms and legs
  • pain in the arms and legs
  • increased sensitivity to cold and heat
  • tight, painful spasms in the arms and legs
  • bladder, bowel, and sexual difficulties

Signs and symptoms of optic nerve inflammation, also called optic neuritis, include:

  • temporary loss of eyesight in at least one eye
  • swelling of the optic disk
  • pain in the eye that can get worse with movement
  • reduced sensitivity to color

People with optic neuritis should not drive, due to vision changes. A person may experience additional symptoms, due to demyelination in the spinal cord.

Some people with NMO also develop TM, which is symmetrical inflammation on both sides of the spinal cord. NMO can also cause demyelination in the spinal cord that is unrelated to TM.

If a person has NMO and TM, this leads to symptoms on both sides of the body and is more likely to cause incontinence.

Other symptoms of TM include:

  • altered sensations, such as increased temperature sensitivity, numbness, tingling, and a burning sensation
  • weakness in the limbs that may lead to complete paralysis
  • changes in urination, including urinary incontinence, difficulty urinating, and more frequent urination
  • fecal incontinence or constipation

A person with NMO may have one mild episode of optic neuritis and one episode of TM, recover, and have no further episodes.

Others may have several episodes throughout their lives and experience lifelong disabilities.

In very rare cases, NMO can affect the brain, and the symptoms depend on the location of the damage. If it affects the lower part of the brainstem, for example, it can cause hiccups or vomiting.

There is no cure, but treatments can ease some of the symptoms and reduce the frequency and intensity of episodes.

These include:

  • Steroids: A doctor may prescribe steroids, such as injected methylprednisolone followed by a course of oral steroids, for acute episodes.
  • Plasma exchange therapy, or plasmapheresis: Doctors typically recommend this when NMO has not responded to steroids. Plasma exchange removes inflammation-causing antibodies from the blood.
  • Relapse-preventing medications: Azathioprine is a medication that suppresses immune activity and can prevent NMO episodes.
  • Immunotherapies: A range of new immunotherapies can significantly reduce the likelihood of experiencing further episodes.

Like other drugs, azathioprine can cause side effects, including:

If damage from NMO is temporary, physical therapy can help a person regain strength. If the damage is permanent, physical therapy can help a person adapt and ease discomfort.

Learn more about treatments for NMO here.

A person’s age at diagnosis, the severity of NMO, and many other factors can affect life expectancy.

The 5-year mortality rate for people who receive treatment is 3–7%. It is 22–30% for people who do not receive treatment. These figures reflect the likelihood of dying from the disease in the 5 years that follow the diagnosis.

Early treatment with plasmapheresis may lead to better long-term outcomes for people with NMO.

And immunotherapies, such as eculizumab, ibalizumab, and rituximab, can significantly reduce the risk of experiencing further NMO episodes.

Learn more about the life expectancy for people with NMO here.

The specific causes of NMO are unknown. It is an autoimmune disorder, and it causes the immune system to mistakenly attack healthy cells in the optic nerve and spinal cord. This causes the symptoms.

The condition does not run in families. In some rare cases, tuberculosis and some environmental organisms may play a role in causing it, though scientists have not been able to isolate the specific organisms responsible.

Many people with NMO have an antibody called neuromyelitis optica immunoglobin G in their blood. Research suggests that this antibody may damage aquaporin-4, the water channel that surrounds the optic nerve and spinal cord cells, causing the characteristic inflammation.

However, confirming this and identifying the full range of causes requires more research.

NMO and multiple sclerosis

Multiple sclerosis (MS) and NMO are both demyelinating autoimmune diseases. Both can cause numbness in the arms and legs, as well as problems with bladder and bowel control.

Symptoms of NMO are generally more severe than symptoms of MS. And unlike the most common forms of MS, NMO is a progressive condition that worsens with each episode.

Meanwhile, brain lesions are a hallmark symptom of MS, but NMO is less likely to affect the brain than the optic nerve and spinal cord. Due to its effects on the brain, people with MS are more likely than people with NMO to have memory or cognitive problems, vertigo, facial pain, and mood changes.

NMO can be difficult to diagnose because the signs and symptoms are often similar to those of:

The following tests can help rule out these conditions, helping doctors diagnose NMO:

  • Blood tests: A doctor can test for neuromyelitis optica immunoglobin G.
  • Lumbar puncture test, or spinal tap: These collect a small amount of fluid from the brain and spinal cord. Results can show high levels of white blood cells and the presence of specific proteins linked to NMO.
  • MRI scan: This scan can show signs of inflammation and scarring in the brain, optic nerve, and spinal cord. An MRI scan can specifically show changes associated with optic neuritis. And in someone with NMO, there may be lesions on three or more segments of the spinal cord, which makes it easier for the doctor to rule out MS.

Most people with NMO experience more than one episode. These can occur months or years apart. Each may damage new areas of the central nervous system and cause cumulative disability.

A majority of people with NMO have some form of permanent limb weakness or vision loss. In severe cases, it can cause total vision loss and arm or leg paralysis. In rare cases, muscle weakness can cause breathing difficulties that require the use of an artificial ventilator.

Treatments may help prevent episodes and resulting disability.

Beyond its symptoms, NMO can cause complications that affect various systems, including:

  • Breathing problems: This can stem from muscle weakness, and a person may need artificial ventilation.
  • Depression: The strain of living with NMO, especially if the symptoms are severe, can lead to depression.
  • Erectile and sexual dysfunction: This may involve difficulty having or maintaining an erection, for people with penises, or trouble reaching orgasm, for anyone.
  • Fragile bones: Long-term steroid therapy can lead to osteoporosis, which weakens the bones and makes them prone to fracture.
  • Paralysis: If NMO severely damages the spinal cord, it can cause limb paralysis.
  • Vision loss: Permanent loss of vision can stem from severe damage to the optic nerve.

The likelihood of complications depends on the severity of the initial episode of NMO and the number of relapses.

A person can find support and resources from these organizations, as well as from healthcare professionals:

  • The Guthy-Jackson Charitable Foundation funds scientific efforts to prevent, treat, and potentially cure NMO spectrum disorder. It hosts a supportive online community and offers a library of information and resources.
  • The Siegel Rare Neuroimmune Association is a nonprofit dedicated to supporting children, teenagers, and adults with a range of rare diseases, including NMO.

NMO is a rare, severe autoimmune disorder that damages the spinal cord, optic nerve, and in some cases, the brain.

Usually, people with NMO have more than one episode and experience cumulative damage. This may involve vision loss and limb weakness or paralysis.

While there is no cure, treatments can reduce the likelihood of future episodes.