Definition

Neuromyelitis optica (NMO) is a disorder of the central nervous system. The central nervous system consists of the brain and spinal cord. NMO causes inflammation and damage to the optic nerve and spinal cord. The optic nerve sends signals from the back of the eye (retina) to the brain. In some cases, NMO also may affect the brain.

Alternative Names

NMO; NMOD; Neuromyelitis optica spectrum disorder; Devic disease; Optic neuritis; Demyelinating disorder; Transverse myelitis

Causes

NMO is a type of autoimmune disorder.

• Autoimmune disorders are conditions where the body’s immune system destroys healthy cells and tissues.
• NMO causes damage to a type of nerve cell called astrocytes as well as the myelin sheath of nerve cells. This sheath is the protective covering that surrounds nerve cells. When this nerve covering is damaged, nerve signals slow or stop. This can occur anywhere along the optic nerve and spinal cord.
• NMO is often confused with and misdiagnosed as multiple sclerosis (MS) because they have similar symptoms. However, the two conditions are different and have different treatments.

There is no identifiable cause for NMO. The disease tends to develop in childhood or in a person's 40s. It may occur after an infection. People with a personal or family history of autoimmune disorders may also be at risk.

There are two main types of NMO:

• Relapsing NMO is the most common form. It has flare-ups that occur between periods of recovery. Women are more likely to get this form of NMO.
• Monophasic NMO is much less common and affects men and women equally. It involves a single attack that may last for 1 to 2 months and does not recur.

Symptoms

NMO may cause different symptoms that range in severity.

One main symptom is inflammation of one or both optic nerves (optic neuritis). Optic nerves transmit images from the eyes to the brain. Swelling and inflammation of the optic nerve may cause eye problems such as:

• Eye pain
• Blurred vision
• Partial vision loss
• Blindness in one or both eyes

Other symptoms include:

• Inflammation of the spinal cord (myelitis)
• Pain around the chest and waist
• Unexplained hiccups
• Persistent nausea or vomiting
• Uncontrollable itching
• Difficulty in swallowing (dysphagia)
• Respiratory disorders
• Problems with movement and coordination (motor or sensory dysfunction)
• Inability to hold stool or urine (bowel or bladder incontinence)
• Brain damage (encephalopathy)
• Double vision
• Sleep disorders such as disturbed sleep, decreased sleep quality, or restless legs syndrome
• Sexual dysfunction
• Recurrent attacks of visual, motor, and sensory dysfunction
• Weakness, numbness, or paralysis of the arms and legs

Your health care provider will do a physical exam and ask about your symptoms and medical history.

Various tests are needed to distinguish NMO from other central nervous system diseases such as multiple sclerosis.

Blood tests may include:

• Complete blood count (CBC)
• Liver function tests (LFTs)
• Thyroid tests

You may have a blood test to detect aquaporin-4 (AQP4) antibodies or myelin oligodendrocyte glycoprotein (MOG) antibodies. The presence of these antibodies in the blood is a specific sign of NMO and can help distinguish it from MS. However, not everyone with NMO has these antibodies.

Other tests may include:

• Magnetic resonance imaging (MRI) to detect lesions of the optic nerves, brain, and spinal cord
• Computed tomography (CT)
• Eye tests and retinal scans
• Lumbar puncture (spinal tap)

Neurological exams may be done to assess your motor or sensory reflexes:

• Limb movement and coordination
• Thinking and memory
• Speech
• Hearing
• Swallowing
• Taste
• Vision

Treatment

There is no cure for NMO. Treatment is focused on relieving symptoms, preventing damage, and preventing attacks long-term.

Treatment during attacks involves:

• Anti-inflammatory medicines such as corticosteroids to treat pain and inflammation during NMO attacks
• Plasma exchange (plasmapheresis) to remove antibodies from the blood if corticosteroids don't work or attacks are severe

Long-term management helps suppress the disease and prevent attacks:

• Monoclonal antibody medicines help prevent attacks of the disease
• Immunosuppressive drugs help prevent attacks

You will also receive therapy to help you manage any lasting effects of the disease such as vision loss and paralysis.

Support Groups

More information and support for people with NMO condition and their families can be found at:

• The Guthy-Jackson Charitable Foundation -- guthyjacksonfoundation.org/nmoresources/
• Siegel Rare Neuroimmune Association -- wearesrna.org/
• The Sumaira Foundation -- www.sumairafoundation.org/

Outlook (Prognosis)

NMO is a chronic disease.

Most people experience recurring NMO attacks (relapsing) while some people may get a one-time attack (monophasic).

Early diagnosis and timely treatment with immunosuppressive drugs improve the outlook. Medicines and therapies can ease the symptoms and people with NMO may live for many years.

People who have monophasic NMO have a better prognosis than those with relapsing NMO.

Possible Complications

Complications may include:

• Severe optic nerve damage leading to vision loss or blindness
• Permanent limb disability
• Paralysis
• Acute respiratory failure

When to Contact a Medical Professional

If you are diagnosed with NMO you should remain in touch with your provider to avoid any further progression in the condition.

Contact your provider immediately if you experience:

• Blurred vision
• Numb limbs
• Severe headache
• Immobility
• Depression

Prevention

There is no known preventive treatment available.

References

Alobeidi F, Thurnher MM, Jäger HR. Non-tumoural spinal cord lesions. In: Adam A, Dixon AK, Gillard JH, Schaefer CM, eds. Grainger & Allison's Diagnostic Radiology. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 50.

Fabian MT, Kriegar SC, Lublin FD. Multiple sclerosis and other inflammatory demyelinating diseases of the central nervous system. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 80.

Gospe SM, Chen JJ, Bhatti MT. Neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein associated disorder-optic neuritis: a comprehensive review of diagnosis and treatment. Eye (Lond). 2021;35(3):753-768. PMID: 33323985 pubmed.ncbi.nlm.nih.gov/33323985/.