Neuromyelitis optica spectrum disorder (NMOSD) is a rare, severe, chronic inflammatory disease of the central nervous system. NMOSD is characterised by inflammation damaging the optic nerve (optic neuritis) and inflammation of the spinal cord (transverse myelitis).
NMOSD presents in attacks. The symptoms are varied, depending on the areas of the central nervous system (CNS) that are affected.
NMOSD mainly presents as optic neuritis (ON) that affects eye function, and/or transverse myelitis (TM) that typically involves long segments of the spinal cord and affects limb, bladder & bowel function.
Other symptoms of NMOSD include sharp pain or muscle twitches through the abdomen, back, or neck. Area postrema syndrome (APS) manifesting as intractable nausea, vomiting, or hiccups (INVH) is also often present.
Optic neuritis may manifest as vision impairment or vision loss, often associated with eye pain or pain on eye movement
Spinal cord inflammation than can lead to muscle weakness or paralysis, reduced sensation, or loss of bladder and bowel control. It can also include pain or discomfort along neck, back or abdomen, or cause area postrema syndrome
Typically, NMOSD presents as a series of attacks also called replases. Neuromyelitis optica is unpredictable.
The frequency and duration of the relapses cannot be predicted and it is currently unknown what trigges them. The neurological deficits occuring during the attack depend on where in the CNS the inflammation is located and also cannot predicted.
NMSOD attacks can last weeks to months. They can resolve with no or minimal residual deficit. However, more often, neurological impairment remains and accumulates over time with each attack.
Untreated, approximately 50% of NMOSD patients will be wheelchair users and blind, and one third will have died within 5 years of their first attack.
Disease-modifying NMOSD treatments therefore aim at avoiding relapses in order to halt neurologic decline and accumulation of permanent disability.
NMOSD and multiple sclerosis (MS) are distinct diseases. The underlying pathology of NMOSD is different from MS.
However, the clinical presentation with relapses and the symptoms of NMOSD can look very similar to that of MS.
Therefore, there is a risk of misdiagnosis of NMOSD.
Treatments for MS are not effective in NMOSD and can even cause deterioration.
An early and correct diagnosis of NMOSD is therefore essential.
NMOSD is a rare disease. The prevalence ranges between 0.5 to 10 cases per 100’000 individuals worldwide.
Ethnic, geographic, and gender disparities are recognized. The numbers are higher in individuals of Asian and African decent. Women are more affected than men. NMOSD can start at any age, but the typical patient is young: the average age at onset is around 40 years.
NMOSD is an autoimmune disorder. This means the body directs an immune response against own healthy cells and tissues. This immune attack causes the symptoms of NMOSD.
A central element of the autoimmune response in typical NMOSD are antibodies directed against a protein called aquaporin-4 (AQP4), which is found on cells in the central nervous system. This antibody directed against aquaporin-4 (AQP4-Ig) is disease-specific and initially had been called NMO-Ig. Its discovery has led to increased understanding of a diverse spectrum of disorders. This spectrum includes a potential subset of patients with a phenotype of NMOSD who have auto-antibodies against other proteins found in the central nervous system, such as anti-myelin oligodendrocyte glycoprotein (MOG).
There is evidence that AQP4-Ig is a key player in the autoimmune response causing damage in NMOSD. A direct role of AQP4-Ig in the disease pathology is documented. Levels of AQP4-Ig in the blood correlate with tissue damage in the CNS and NMOSD disease activity.
Recent approaches to disease modifying therapy in NMOSD - including that of Chord Therapeutics - target either the production or biological function of AQP4-Ig.
The symptoms of NMOSD can vary from person to person in disability, duration and severity, and may as well become worse over time.
If you or a family member is diagnosed with NMOSD, it is important to build a support system that includes family, friends, professionals, and support groups. A person with significant disabilities may need the support of specialized neurologists, occupational therapists, physical therapists, and social services professionals.
There is currently no cure for NMOSD, but treatments can help to ease symptoms, prevent future relapses and slow the progression of the disease. NMOSD can be treated on three levels:
NMOSD can have a significant impact on your quality of life, but support is available.
See a GP if you have any of the symptoms described above on this page.
Your GP will refer you to a neurologist (specialist in diseases of the nerves) for further testing to confirm the diagnosis and rule out any other conditions with similar symptoms, such as multiple sclerosis (MS).
Your healthcare provider may do a variety of tests NMOSD is suspected, including:
MRI scan of your brain and spinal cord
Blood tests
Tests to check on how well your optic nerves are working
Lumbar puncture, where a sample of the cerebrospinal fluid is tested
First publication of NMO cases by Eugene Devic
First modern systematic evaluation of NMO defining diagnostic criteria based on optic neuritis and transverse myelitis
Identification of the association of AQP4 autoantibody with NMO pathology
AQP4-Ig antibody test added to NMO diagnostic criteria, increasing the accuracy of diagnosis.
Concept of neuromyelitis optica spectrum disorders introduced.
Publication of the current International Consensus Diagnostic Criteria of Neuromyelitis Optica Spectrum Disorders.
