Neuromyelitis optica

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Neuromyelitis optica is an autoimmune disorder that affects the nerves of the eyes and the central nervous system, which includes the brain and spinal cord. Autoimmune disorders occur when the immune system malfunctions and attacks the body's own tissues and organs. In neuromyelitis optica, the autoimmune attack causes inflammation of the nerves, and the resulting damage leads to the signs and symptoms of the condition.

Neuromyelitis optica is characterized by optic neuritis, which is inflammation of the nerve that carries information from the eye to the brain (optic nerve). Optic neuritis causes eye pain and vision loss, which can occur in one or both eyes.

Neuromyelitis optica is also characterized by transverse myelitis, which is inflammation of the spinal cord. The inflammation associated with transverse myelitis damages the spinal cord, causing a lesion that often extends the length of three or more bones of the spine (vertebrae). In addition, myelin, which is the covering that protects nerves and promotes the efficient transmission of nerve impulses, can be damaged. Transverse myelitis causes weakness, numbness, and paralysis of the arms and legs. Other effects of spinal cord damage can include disturbances in sensations, loss of bladder and bowel control, uncontrollable hiccupping, and nausea. In addition, muscle weakness may make breathing difficult and can cause life-threatening respiratory failure in people with neuromyelitis optica.

There are two forms of neuromyelitis optica, the relapsing form and the monophasic form. The relapsing form is most common. This form is characterized by recurrent episodes of optic neuritis and transverse myelitis. These episodes can be months or years apart, and there is usually partial recovery between episodes. However, most affected individuals eventually develop permanent muscle weakness and vision impairment that persist even between episodes. For unknown reasons, approximately nine times more women than men have the relapsing form. The monophasic form, which is less common, causes a single episode of neuromyelitis optica that can last several months. People with this form of the condition can also have lasting muscle weakness or paralysis and vision loss. This form affects men and women equally. The onset of either form of neuromyelitis optica can occur anytime from childhood to adulthood, although the condition most frequently begins in a person's forties.

Approximately one-quarter of individuals with neuromyelitis optica have signs or symptoms of another autoimmune disorder such as myasthenia gravis, systemic lupus erythematosus, or Sjögren syndrome. Some scientists believe that a condition described in Japanese patients as optic-spinal multiple sclerosis (or opticospinal multiple sclerosis) that affects the nerves of the eyes and central nervous system is the same as neuromyelitis optica.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

No genes associated with neuromyelitis optica have been identified. However, a small percentage of people with this condition have a family member who is also affected, which indicates that there may be one or more genetic changes that increase susceptibility. It is thought that the inheritance of this condition is complex and that many environmental and genetic factors are involved in the development of the condition.

The aquaporin-4 protein (AQP4), a normal protein in the body, plays a role in neuromyelitis optica. The aquaporin-4 protein is found in several body systems but is most abundant in tissues of the central nervous system. Approximately 70 percent of people with this disorder produce an immune protein called an antibody that attaches (binds) to the aquaporin-4 protein. Antibodies normally bind to specific foreign particles and germs, marking them for destruction, but the antibody in people with neuromyelitis optica attacks a normal human protein; this type of antibody is called an autoantibody. The autoantibody in this condition is called NMO-IgG or anti-AQP4.

The binding of the NMO-IgG autoantibody to the aquaporin-4 protein turns on (activates) the complement system, which is a group of immune system proteins that work together to destroy pathogens, trigger inflammation, and remove debris from cells and tissues. Complement activation leads to the inflammation of the optic nerve and spinal cord that is characteristic of neuromyelitis optica, resulting in the signs and symptoms of the condition.

The levels of the NMO-IgG autoantibody are high during episodes of neuromyelitis optica, and the levels decrease between episodes with treatment of the disorder. However, it is unclear what triggers episodes to begin or end.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Neuromyelitis optica is usually not inherited. Rarely, this condition is passed through generations in families, but the inheritance pattern is unknown.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Neuromyelitis optica affects approximately 1 to 2 per 100,000 people worldwide. Women are affected by this condition more frequently than men.

Which doctor should you see?

The suggested department for discussing Neuromyelitis optica is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Neuromyelitis optica. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.