Neuromyelitis Optica Spectrum Disorder – Neuromyelitis Optica Spectrum Disorder (NMOSD) is an autoimmune disease in which the immune system mistakenly attacks the optic nerves (optic neuritis) and the spinal cord (myelitis); it can also attack the brain.
Neuromyelitis Optica Spectrum Disorder is also referred to as Neuromyelitis Optica (NMO) and Devic’s Disease.
What is Neuromyelitis Optica?
The cause of NMO is usually unknown, although it may sometimes appear after an infection, or it may be associated with another autoimmune condition. Neuromyelitis Optica is often misdiagnosed as Multiple Sclerosis (MS) but NMO has it’s own distinct characteristics.
Neuromyelitis optica may cause blindness in one or both eyes, weakness or paralysis in the legs or arms, painful spasms, loss of sensation, uncontrollable vomiting and hiccups, and bladder or bowel dysfunction from spinal cord damage. Children may experience confusion, seizures or coma with NMO. Neuromyelitis optica flare-ups may be reversible, but can be severe enough to cause permanent visual loss and problems with walking.
Neuromyelitis Optica Symptoms
+ Pain in the eyes.
+ Paralysis of the arms and legs.
+ The characteristic symptoms of NMOSD are either optic neuritis or myelitis; either may occur as the first symptom. Optic neuritis is inflammation, of the optic nerve (optic neuritis) leading to pain inside the eye which rapidly is followed by loss of clear vision (acuity). Usually, only one eye is affected (unilateral) although both eyes may be involved simultaneously (bilateral). NMOSD may or may not be preceded by a prodromal upper respiratory infection.
+ Loss of vision.
+ Difficulty controlling the bladder or bowels.
+ The other cardinal syndrome is inflammation of the spinal cord, a condition known as transverse myelitis because the symptoms tend to affect some, and often all motor, sensory and autonomic functions (bladder and bowel) below a certain level on the body, although, not infrequently, symptoms may be confined to one side of the body. Affected individuals may experience pain in the spine or limbs, and mild to severe paralysis (paraparesis to paraplegia) of the lower limbs, and loss of bowel and bladder control. Deep tendon reflexes may be exaggerated, or may be diminished or absent initially and later become exaggerated. A variable degree of sensory loss may occur. Affected individuals may also have a stiff neck, back or limb pain, and/or headaches. This syndrome may be indistinguishable from other cases of “idiopathic” transverse myelitis.
+ Weakness or numbness in the arms and legs.
+ Uncontrollable vomiting and hiccups.
+ Early in the course of the disease, it may be difficult to distinguish between NMOSD and multiple sclerosis because both may cause optic neuritis and myelitis as symptoms. However, the optic neuritis and myelitis tend to be more severe in NMOSD; the brain MRI is more commonly normal, and the spinal fluid analysis does not usually show oligoclonal bands in NMOSD, which are features that help distinguish it from MS.oligoclonal bands in NMOSD, which are features that help distinguish it from MS.
Neuromyelitis Optica Diagnosis
A diagnosis of NMOSD is made based upon a detailed patient history, a thorough clinical evaluation, identification of characteristic physical findings, and a variety of specialized tests while working with a neurologist. Such tests include blood tests, examination of cerebrospinal fluid (CSF), spinal taps, or x-ray procedures such as magnetic resonance imaging (MRIs) or computed tomography (CT or CAT) scans.
A blood test, AQP4-IgG, is highly specific and moderately sensitive for NMOSD. It has been shown that it detects antibodies that are specific for an astrocyte protein, aquaporin-4. This is very helpful to request this test at the first significant suspicion of NMOSD, as it is frequently positive at the time of the very first symptom even before a confident clinical diagnosis is possible.
A recently discovered antibody, MOG-IgG, is present in about half of those who do not have AQP4-IgG; while it seems specific for a form of NMOSD, and is rarely seen in typical MS, it also occurs in some patients with recurrent optic neuritis and in some patients with acute disseminated encephalomyelitis; in the latter patients, it is often transient. Successful diagnosis of NMOSD depends on distinguishing it from MS.
Treatment for Neuromyelitis Optica
For acute attacks, the standard treatment is high-dose intravenous corticosteroids, typically methylprednisolone. Plasma exchange may be effective in patients who experience acute severe attacks that do not response to intravenous corticosteroids. This procedure involves removing some blood and mechanically separating the blood cells from the fluid (plasma). Blood cells are then mixed with a replacement solution and returned to the body.
For long-term suppression of the disease, no specific treatment has been studied in controlled clinical trials, but a variety of immunosuppressive drugs are regarded by many clinicians as first-line therapy. Corticosteroids, azathioprine, mycophenolate mofetil and rituximab are the treatments most widely prescribed treatments. Typically, azathioprine or mycophenolate mofetil are prescribed along with low doses of corticosteroids. Rituximab has been shown to be helpful in retrospective studies, including in patients who fail first-line immunosuppressive treatments. Immunomodulatory drugs for multiple sclerosis are ineffective, and in the case of interferon beta, there is some evidence that suggest that it may be harmful.
Symptom treatment may also involve the use of low doses of carbamazepine to control paroxysmal (sudden) tonic spasms that often occur during attacks of NMOSD and antispasticity agents to treat long term complication of spasticity that frequently develops in those with permanent motor deficits.