What Is Devic's Disease? What Is Neuromyelitis Optica? What Causes Devic's Disease?

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Main Category: Eye Health / Blindness
Also Included In: Neurology / Neuroscience;  Immune System / Vaccines
Article Date: 09 Nov 2009 - 5:00 PST

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Devic's disease, or neuromyelitis optica, (NMO) is a type of inflammatory demyelinating disease. A demyelinating disease occurs when the myelin sheath, a protective covering that surrounds brain and spinal cord nerves is damaged. In the case of Devic's disease, the patient develops myelitis (inflammation of the spinal cord) and optic neuritis (inflammation of the optic nerve).

According to the National Health Service, UK, a higher percentage of people of African and Asian ancestry develop Devic's disease, compared to other people. However, anybody can be affected. The disease more commonly affects people when they are about 40 years of age.

According to Medilexicon's medical dictionary, neuromyelitis optica is "a demyelinating disorder consisting of a transverse myelopathy and optic neuritis"

There are two main types of neuromyelitis optica:

• Relapsing neuromyelitis optica
  
  There is an initial attack of optic neuritis and transverse myelitis, and then subsequent attacks over a period of several years. Sometimes the patient cannot recover fully from the neurological damage the attacks cause to the optic nerve and/or spinal cause and the damage is permanent, causing disability. This type of neuromyelitis optica affects females more frequently than males.


• Monophasic neuromyelitis optica
  
  Few attacks are experienced over a period of days or weeks. There are no subsequent attacks. This form of neuromyelitis optica affects both sexes equally.

What are the signs and symptoms of neuromyelitis optica?

A symptom is something the patient feels and reports, while a sign is something other people, including a doctor or nurse may detect. For example, pain may be a symptom while a rash may be a sign.

Signs and symptoms of neuromyelitis optica (NMO) vary according to many factors, including the type of NMO the patient has. Typically, a person with NMO will have at least one episode of optic neuritis and transverse myelitis.

Signs and symptoms of optic neuritis include (ON):

• The optic nerve becomes inflamed


• Loss of eyesight, which affects at least one eye. In most cases this is temporary; however, there is a risk of permanent vision loss, which is exacerbated by heat or exercise.


• Swelling of the optic disc.


• Pain in the eye. The pain generally worsens with movement. Pain becomes more intense after about one week, and then goes away after a period of days.


• The eyes become less sensitive to colors.

Patients who develop optic neuritis may have problems driving a vehicle.

Signs and symptoms of transverse myelitis (TM):

• The spinal cord becomes inflamed


• Back pain


• Neck pain


• Shooting sensations in the limbs and abdomen


• Below the affected area of the spinal cord the patient may have altered sensations, with sensitivity to cold/heat, numbness, tingling, and a sensation of coldness or burning.


• Limbs may become weak. Some patients may describe their limbs as feeling heavy, while others may develop total paralysis.


• Urinary incontinence


• More frequent urination


• Difficulty urinating


• Fecal incontinence (bowel incontinence)


• Constipation


• Difficulty in completely emptying the bowels

A patient with NMO may have just one mild attack of ON and one episode of TM, recover completely, or almost completely, and have no more relapses ever. Others may have several attacks throughout their life and experience lifelong disability.

NMO spectrum disorder is a term used for patients who experience only relapsing optic neuritis or relapsing myelitis (but not both).

In most cases, just the optic nerve and spinal cord of patients with NMO are affected. In very rare cases parts of the brain may also be affected. Patient's whose brain stem has been affected may experience uncontrollable hiccups or vomiting.

What are the causes of neuromyelitis optica?

Experts are not sure what the exact causes of NMO are. We do know that the following factors are or aren't implicated in the disease:

• It is not apparently, a strongly hereditary condition; it does not usually run in families.


• A higher percentage of people from Asia or Africa, as well as individuals of Asian or African ancestry develop NMO, compared to other people. This fact indicates that hereditary must play some part.


• In some rare cases, TB (tuberculosis) and some environmental organisms have been linked to the development of NMO. However, scientists have not been able to isolate specific organisms so far.


• NMO is an autoimmune disorder. Healthy people's immune systems attack pathogens; organisms and substances that are bad for us, such as some bacteria, viruses, parasites, cancer cells and fungi. If the person's immune system starts attacking good tissue, they have an autoimmune disease (disorder) - the immune system is attacking parts of the person's body that are needed for good health. NMO is an example of an autoimmune disease. Experts are not sure why autoimmune diseases, such as NMO occur. The immune system of a patient with NMO attacks the myelin sheath, the protective blanket for the spinal cord and optic nerve.


• Scientists have revealed that over two-thirds of patients with NMO have an antibody called NMO IgG (Neuromyelitis Optica Immunoglobin G) in their blood. Scientists say that most likely NMO IgG damages Aquaporin 4, the water channel that surrounds optic nerve and spinal cord cells, resulting in NMO.

How is neuromyelitis optica (NMO) diagnosed?

NMO is not an easy condition to diagnose because it presents signs and symptoms which are often similar to those found in other diseases, such as:

• MS (multiple sclerosis)
• ADEM (acute demyelinating encephalomyelitis)
• SLE (systemic lupus erythematosis), also known as Sjogren's syndrome
• MCTD (mixed connective tissue disorder)
• Some inflammations caused by viruses
• Paraneoplastic optic neuropathy (inflammation linked to cancer)

The doctor will have to carry out some tests to rule out the above-mentioned conditions.

• Blood test - the aim here is to find out whether the antibody NMO IgG is present. A positive blood test result usually means that the patient risks having multiple attacks of transverse myelitis.


• Lumbar puncture test (spinal tap) - a small amount of fluid surrounding the brain and spinal cord is collected. Results will indicate whether levels of white blood cells are high, and also whether specific proteins linked to NMO or other conditions are present.


• MRI (magnetic resonance imaging (MRI) scan - this scan can show up any damage to nerves and their surroundings (lesions). MRI scans of NMO patients hardly ever reveal any brain abnormalities, but will show up lesion consisting of three or more segments of the spinal cord. This type of spinal cord lesion makes it easier for the doctor to rule out multiple sclerosis.

What are the treatment options for neuromyelitis optica (NMO)?

NMO is not a curable disease. However, there are some treatments which may help some of the symptoms and relapse frequency and intensity.

• Treatment of relapses
  
  
  • Steroids - such steroids as injected methylprednisone may be administered, after which the patient would take a course of oral steroids.
  
  
  • Plasma exchange therapy (Plasmapheresis) - this treatment is usually only given to patients who have not responded to the attacks with steroid treatment. Plasma exchange removes the inflammation-causing antibodies from the blood. The patient's blood is removed and blood cells are separated from plasma. The blood cells, diluted with fresh plasma or substitute are returned to the patient's bloodstream.


• Preventing relapses
  
  If the patient's immune system can be slightly suppressed the chances of relapses are significantly reduced. AZT (azathioprine), an immunosuppressant medication is sometimes prescribed. The doctor may prescribe a combination of AZT and steroids. AZT may cause vomiting, diarrhea, fever, hypotension (low blood pressure), dizziness, pneumonitis, colitis, hair loss and pancreatitis.


• Controlling symptoms
  
  The anticonvulsant drug, carbamazepine, may be prescribed for symptoms of pain, urinary problems, muscle spasms, and stiffness. Carbamazepine is often used with patients who have other demyelinating diseases.


• Rehabilitation
  
  If damage is permanent and the patient experiences disabilities, physical therapy (physiotherapy), rehabilitation, mobility and visual aids may also be given.

What are the possible complications of neuromyelitis optica (NMO)?

• Breathing problems - in severe cases muscle weakness may be such that the patient needs artificial ventilation.


• Depression - the mental strain of living with NMO, especially if symptoms are severe, can lead to clinical depression.


• Erectile dysfunction and sexual dysfunction - some men may experience problems getting or maintaining an erection. Both men and women may experience problems reaching orgasm.


• Fragile bones - long-term steroid therapy can lead to osteoporosis.


• Paralysis - in severe cases when there is damage to the spinal cord, there can be limb paralysis.


• Vision loss - in severe cases there can be damage to the optic nerve, leading to permanent loss of vision.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today