Demyelinating disease
Demyelination occurs when the myelin sheath surrounding nerve fibers is damaged. Myelin is a protective sheath that wraps around the nerve fibers. It helps nerve cells to transmit nerve signals at a higher speed. Myelinated neurons can send a signal at over 100 meters per second, whereas unmyelinated neurons can send signals at just 1 meter per second. Myelin allows the quick and efficient transmission of nerve signals along the connecting fibers of nerve cells. When nerve cells can send, receive, and process signals in the brain, we can speak, see, feel, and think properly. Myelin can be damaged due to medical conditions, causing the deterioration of axons, which are nerve fibers sending electrical impulses away from the neurons. This loss of axons can cause problems with our ability to feel, move, see, hear, and think.
How many types of demyelination?
- Inflammatory demyelination: This condition happens when the immune system mistakenly attacks the myelin sheath.
Inflammation of peripheral nerves innervating the face, limbs, and organs can lead to Guillain-Barré syndrome (GBS). Inflammation in the central nervous system, comprising the brain and spinal cord, causes multiple sclerosis (MS), optic neuritis, and acute-disseminated encephalomyelitis.
MS is the most common demyelinating condition, affecting 2.3 million people worldwide. Lesions of MS involve the white matter of the brain and the spinal cord. There are many types of MS, such as:
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- Relapsing-remitting MS
- Primary progressive MS
- Secondary progressive MS
- Clinically isolated syndrome
- Viral demyelination
Progressive multifocal leukoencephalopathy (PML) (JC virus), subacute sclerosing panencephalitis (SSPE) (measles virus), and postinfectious encephalomyelitis (often following viral infections) are examples of viral demyelinating diseases.
What causes demyelination?
- Inflammation, the most common cause of demyelination
- Autoimmunity
- Viral infections
- Oxygen deprivation, which can cause hypoxic-ischemic demyelination
- Metabolic disorders
- Physical compression of a nerve
- Alcoholism
- Liver damage
- Electrolyte imbalances
- Toxin exposures
- Nutrient deficiencies, e.g., vitamin B12, copper
What are the symptoms of demyelination?
Symptoms of demyelination vary in different people, but they can rapidly appear. People with Guillain-Barré syndrome (GBS) can develop symptoms a couple of hours after myelin is under attack.
Common symptoms include:
- Vision loss
- Bowel and bladder dysfunction
- Nerve pain
- Rapid heartbeat
- Memory problems
Symptoms are chronic. They can come and go and progress over the years.
How is demyelination diagnosed?
Imaging tests such as MRI can help diagnose MS and optic neuritis. MRI detects demyelination plaques in the brain and nerves, enabling targeted treatment of lesions.
How is demyelinating disease treated?
Currently, there is no cure for demyelination. Researchers have found that myelin can regrow, but it is typically thinner and has less efficient function. Research is ongoing on how to stimulate the body to grow new myelin more effectively. Treatments aim to minimize the inflammatory immune response, manage pain, and improve the quality of life of patients.
Doctors typically prescribe medications such as interferon beta-1a or glatiramer acetate to treat the disease. In some studies, statins can delay cognitive decline and the onset of Alzheimer’s disease. However, more studies are required. Vaccines and demyelination
Some people who have hypersensitive immune systems can experience acute demyelinating syndromes after exposure to influenza or HPV vaccines, but this is very rare.