Disorders that cause demyelination Overview of Demyelinating Disorders Most nerve fibers inside and outside the brain are wrapped with many layers of tissue composed of a fat (lipoprotein) called myelin. These layers form the myelin sheath. Much like the insulation... read more and have no known cause are called primary demyelinating disorders. Demyelination is the destruction of the tissues that wrap around nerves, called the myelin sheath.
Insulating a Nerve Fiber
Most nerve fibers inside and outside the brain are wrapped with many layers of tissue composed of a fat (lipoprotein) called myelin. These layers form the myelin sheath. Much like the insulation around an electrical wire, the myelin sheath enables nerve signals (electrical impulses) to be conducted along the nerve fiber with speed and accuracy. When the myelin sheath is damaged (called demyelination), nerves do not conduct electrical impulses normally.
Sometimes primary demyelinating disorders develop after a viral infection or vaccination against a viral infection. A likely explanation is that the virus or another substance somehow triggers the immune system to attack the body’s own tissues (autoimmune reaction Autoimmune Disorders An autoimmune disorder is a malfunction of the body's immune system that causes the body to attack its own tissues. What triggers an autoimmune disorder is not known. Symptoms vary depending... read more ). The autoimmune reaction results in inflammation, which damages the myelin sheath and the nerve fiber under it.
Multiple sclerosis Multiple Sclerosis (MS) In multiple sclerosis, patches of myelin (the substance that covers most nerve fibers) and underlying nerve fibers in the brain, optic nerves, and spinal cord are damaged or destroyed. The cause... read more is the most common primary demyelinating disorder.
Acute Disseminated Encephalomyelitis (ADEM)
This rare type of inflammation leads to demyelination Overview of Demyelinating Disorders Most nerve fibers inside and outside the brain are wrapped with many layers of tissue composed of a fat (lipoprotein) called myelin. These layers form the myelin sheath. Much like the insulation... read more of nerves in the brain and spinal cord. Acute disseminated encephalomyelitis is more common among children than among adults.
Acute disseminated encephalomyelitis usually develops after a viral infection. Acute disseminated encephalomyelitis is thought to be a misguided immune reaction triggered by the virus. In the United States, this disorder usually results from some types of influenza Influenza (Flu) Influenza (flu) is a viral infection of the lungs and airways with one of the influenza viruses. It causes a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general... read more , hepatitis A Hepatitis A Acute hepatitis A is inflammation of the liver that is caused by the hepatitis A virus and that lasts less than 6 months. Hepatitis A is usually spread when people ingest something that has... read more , hepatitis B Hepatitis B, Acute Acute hepatitis B is inflammation of the liver that is caused by the hepatitis B virus and that lasts from a few weeks up to 6 months. Hepatitis B is spread through contact with blood or other... read more , or infection with enteroviruses Overview of Enterovirus Infections Enterovirus infections affect many parts of the body and may be caused by any of several different strains of enterovirus. Enterovirus infections are caused by many different viruses. Symptoms... read more , Epstein-Barr virus Infectious Mononucleosis Epstein-Barr virus causes a number of diseases, including infectious mononucleosis. The virus is spread through kissing. Symptoms vary, but the most common are extreme fatigue, fever, sore throat... read more , or human immunodeficiency virus Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and is treated with antiretroviral medications. If untreated, it can cause... read more (HIV). Measles Measles Measles is a highly contagious viral infection that causes various cold-like symptoms and a characteristic rash. Measles is caused by a virus. Symptoms include fever, runny nose, hacking cough... read more , chickenpox Chickenpox Chickenpox is a highly contagious viral infection with the varicella-zoster virus that causes a characteristic itchy rash, consisting of small, raised, blistered, or crusted spots. Chickenpox... read more , and rubella Rubella Rubella is a contagious viral infection that typically causes mild symptoms, such as joint pain and a rash, but can cause severe birth defects if the mother becomes infected with rubella during... read more used to be common causes before childhood vaccination became widespread.
Typically, the inflammation develops 1 to 3 weeks after the viral illness begins.
Symptoms of ADEM
Symptoms of acute disseminated encephalomyelitis appear rapidly. At first, people may have a fever, a headache, nausea, and vomiting and feel tired. When the disorder is severe, it can cause seizures and coma.
Vision in one or both eyes may be lost. Muscles may become weak, and coordination may be impaired, making walking difficult. People may become paralyzed. Sensation may be lost in parts of the body, making them feel numb. Mental function (including thinking, judgment, and learning) may be affected.
Most people recover within days, and within 6 months, most have totally or almost totally recovered. Other people may remain impaired the rest of their life. Muscles may remain weak, and areas of the body may remain numb. People may not recover their vision or mental function.
Diagnosis of ADEM
A doctor's evaluation
Doctors may be able to diagnose acute disseminated encephalomyelitis based on symptoms and results of a physical examination. Magnetic resonance imaging (MRI) may be done.
A spinal tap Spinal Tap Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Electroencephalography (EEG) is a simple, painless procedure in which... read more (lumbar puncture) may be done to check for meningitis or a brain infection (encephalitis). Blood tests may be done to check for other disorders that cause similar symptoms.
Treatment of ADEM
Immune globulin or plasma exchange
Acute disseminated encephalomyelitis can be treated with corticosteroids given intravenously.
Immune globulin and plasma exchange Plateletpheresis (platelet donation) In addition to normal blood donation and transfusion, special procedures are sometimes used. In plateletpheresis, a donor gives only platelets rather than whole blood. Whole blood is drawn from... read more may also be effective. These treatments may be used with or without corticosteroids. Immune globulin consists of antibodies obtained from the blood of people with a normal immune system. For plasma exchange, blood is withdrawn, abnormal antibodies are removed from it, and the blood is returned to the person.
Adrenoleukodystrophy and Adrenomyeloneuropathy
Adrenoleukodystrophy X-linked adrenoleukodystrophy Peroxisomal disorders are a group of hereditary metabolic disorders that occur when peroxisomes are missing or do not function correctly in the body. Hereditary disorders occur when parents... read more and adrenomyeloneuropathy X-linked adrenoleukodystrophy are rare hereditary metabolic disorders. In these disorders, fats are not broken down as they normally are. These fats accumulate mainly in the brain, spinal cord, and adrenal glands. In the brain, they cause demyelination of nerves.
Adrenoleukodystrophy affects young boys, usually between the ages of 4 and 8. A milder, more slowly developing form of the disorder can begin during adolescence or young adulthood.
Adrenomyeloneuropathy is a milder form. It begins when men are in the 20s or 30s,
In these disorders, widespread demyelination Overview of Demyelinating Disorders Most nerve fibers inside and outside the brain are wrapped with many layers of tissue composed of a fat (lipoprotein) called myelin. These layers form the myelin sheath. Much like the insulation... read more is often accompanied by adrenal gland dysfunction Adrenal disorders The body has two adrenal glands, one near the top of each kidney. They are endocrine glands, which secrete hormones into the bloodstream. Each adrenal gland has two parts. Medulla: The inner... read more . Boys have behavioral problems and problems with hearing and vision. Eventually, mental deterioration, involuntary and uncoordinated muscle contractions (spasticity), and blindness occur. Some boys with adrenoleukodystrophy are totally disabled or die 2 to 3 years after diagnosis. Often, adults with adrenomyeloneuropathy first notice a problem when their legs become weak and stiff, they lose control of their bladder or bowels (incontinence), and/or erectile dysfunction develops.
The diagnosis of adrenoleukodystrophy or adrenomyeloneuropathy is confirmed by genetic testing.
No cure for either disorder is known. Dietary supplements with glycerol trioleate and glycerol trierucate (known as Lorenzo’s oil) may help, but further study is needed.
When the adrenal gland (but not the brain) is affected, treatment with adrenal hormones may be lifesaving. Many experts now recommend stem cell transplantation Stem Cell Transplantation Stem cell transplantation is the removal of stem cells (undifferentiated cells) from a healthy person and their injection into someone who has a serious blood disorder. (See also Overview of... read more early in the disease before serious symptoms develop.
Leber Hereditary Optic Neuropathy
Leber hereditary optic neuropathy causes demyelination Overview of Demyelinating Disorders Most nerve fibers inside and outside the brain are wrapped with many layers of tissue composed of a fat (lipoprotein) called myelin. These layers form the myelin sheath. Much like the insulation... read more leading to partial loss of vision.
Leber hereditary optic neuropathy is more common among men. Usually, symptoms begin between the ages of 15 and 35. This disorder is inherited through the mother, and the defective genes seem to be located in mitochondria (structures in cells that provide energy for the cell).
Vision may become blurred in one eye or in both eyes at the same time. But if vision in one eye is affected, vision in the other eye begins to be lost within weeks or months. The sharpness of vision (acuity) and color vision deteriorate over time.
Some people also have heart problems or muscle symptoms (such as involuntary muscle contractions, muscle weakness, or muscle spasms), which may resemble symptoms of multiple sclerosis Multiple Sclerosis (MS) In multiple sclerosis, patches of myelin (the substance that covers most nerve fibers) and underlying nerve fibers in the brain, optic nerves, and spinal cord are damaged or destroyed. The cause... read more .
Doctors can often diagnose Leber hereditary optic neuropathy based on symptoms and results of a physical examination. Testing can identify some of the abnormal genes responsible for the disorders. Electrocardiography Echocardiography and Other Ultrasound Procedures Ultrasonography uses high-frequency (ultrasound) waves bounced off internal structures to produce a moving image. It uses no x-rays. Ultrasonography of the heart (echocardiography) is one of... read more is done to check for the heart problems.
There is no established treatment for Leber hereditary optic neuropathy. However, some evidence suggests that the drugs idebenone and ubiquinone may improve sight in people with Leber hereditary optic neuropathy, but they cannot reverse damage already done to the optic nerve. Gene therapy is being studied. It involves injecting the normal gene into the eye.
Limiting consumption of alcohol and not using tobacco products may help. Alcohol and tobacco may affect the mitochondria, which is where the defective gene that causes Leber hereditary optic neuropathy is located.