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Demyelination: What Is It and Why Does It Happen?

What is demyelination?

Nerves send and receive messages from every part of your body and process them in your brain. Nerves allow you to speak, see, feel, and think.

Many nerves are coated in myelin. Myelin is an insulating material. When it’s worn away or damaged, nerves can deteriorate, causing problems in the brain and throughout the body. Damage to myelin around nerves is called demyelination.

Nerves

Nerves are made up of neurons. Neurons are composed of a cell body, dendrites, and an axon. The axon sends messages from one neuron to the next. The axon also connects neurons to other cells, such as muscle cells.

Some axons are extremely short. Others are 3 feet long. Some axons are covered in myelin. Myelin protects the axons and helps carry axon messages as quickly as possible.

Myelin

Myelin is made of membrane layers that cover an axon. This is similar to the idea of an electrical wire with coating to protect the metal underneath.

Myelin allows a nerve signal to travel faster. In unmyelinated neurons, a signal can travel along the nerves at about 1 meter per second. In a myelinated neuron, the signal can travel 100 meters per second.

Certain diseases can damage myelin. Demyelination slows down messages sent along axons and causes the axon to deteriorate. Depending upon the location of the damage, axon loss can cause problems with feeling, moving, seeing, hearing, and thinking clearly.

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Causes

Causes of demyelination

Inflammation is the most common cause of myelin damage. Other causes include:

  • certain viral infections
  • metabolic problems
  • loss of oxygen
  • physical compression

Symptoms

Symptoms of demyelination

Demyelination prevents nerves from being able to conduct messages to and from the brain. The effects of demyelination can occur rapidly. In Guillain-Barre syndrome (GBS), myelin may only be under attack for a few hours before symptoms appear.

Symptoms can come and go in chronic illnesses like multiple sclerosis (MS) and progress over years. Nerves are a key part of your body functions. Thus, a wide range of symptoms can occur when nerves are affected by demyelination, including:

  • numbness
  • loss of reflexes and uncoordinated movements
  • poorly controlled blood pressure
  • blurred vision
  • dizziness
  • racing heart beat or palpitations
  • memory problems
  • pain
  • loss of bladder and bowel control
  • fatigue

Early symptoms of demyelination

Not everyone is affected by demyelinating diseases in the same way. However, some demyelinating symptoms are very common. Early symptoms include:

  • loss of vision
  • bladder or bowel problems
  • unusual nerve pain
  • overall fatigue

These are among the first signs of a demyelinating disease.

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Types

Types of demyelination

There are different types of demyelination. These include inflammatory demyelination and viral demyelination.

Inflammatory demyelination

Inflammatory demyelination happens when the body’s immune system attacks myelin. Types of demyelination like MS, optic neuritis, and acute-disseminated encephalomyelitis are caused by inflammation in the brain and spinal cord. GBS involves inflammatory demyelination of peripheral nerves in other parts of the body.

Viral demyelination

Viral demyelination occurs with progressive multifocal leucoencephalopathy (PML). PML is caused by the JC virus. Myelin damage can also occur with alcoholism, liver damage, and electrolyte imbalances. Hypoxic-ischemic demyelination occurs due to a lack of oxygen or vascular disease in the brain.

MS and Demyelination

Demyelination and multiple sclerosis

MS is the most common demyelinating disease. According to the National MS Society, it affects 2.3 million people worldwide. In MS, demyelination occurs in the white matter of the brain and in the spinal cord. Lesions or “plaques” then form where myelin is under attack by the immune system. Many of these plaques (or scar tissue) occur throughout the brain over the course of years.

The types of MS are:

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Treatment and Diagnosis

Treatment and diagnosis

There is no cure for demyelinating diseases. New myelin growth can occur in areas of damage. But new myelin is thinner and not as effective. Researcher are looking into ways to increase the body’s ability to grow new myelin.

Most treatments of demyelinating disease reduce the immune response. This is done with drugs like interferon beta-1a or glatiramer acetate. Also, people with low levels of vitamin D more easily develop MS or other demyelinating diseases. High levels of vitamin D may reduce inflammatory immune response.

Demyelination MRI

Demyelinating diseases, especially MS and optic neuritis (inflammation of the optic nerve), are detectable with MRI scans. MRIs can show demyelination plaques in the brain and nerves, especially those caused by MS. Your doctor may be able to locate plaques or lesions affecting your nervous system. Then, treatment can be directed specifically at the source of demyelination in your body.

A closer look: Multiple sclerosis MRI images of the brain »

A note on statins

The central nervous system (CNS) is able to produce its own cholesterol. Current studies show that if you take statins to reduce the cholesterol in your body, they are not likely to affect your CNS cholesterol. Many studies have also found that statin treatment may protect against Alzheimer’s Disease (AD) in patients who have not already experienced cognitive impairment and are still relatively young. Researchers have found that statins may slow the rate of cognitive decline and delay the onset of AD. Research continues, and we don’t have a definite answer yet. Some studies show that statins do not affect the CNS or remyelination, and still others say they do.

Currently, most of the evidence does not show statin therapy to be harmful to remyelination within the CNS. Still, the effects of statins on cognitive function remain controversial at this time.

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Vaccines

Vaccines and demyelination

Activating the immune system with a vaccine can trigger an autoimmune reaction. This tends to occur only in a few individuals with hypersensitive immune systems. Some children and adults experience “acute demyelinating syndromes” after exposure to certain vaccines, such as those for influenza or HPV. But there have only been 77 documented cases since 1979.

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Takeaway

The takeaway

Demyelinating diseases can seem painful and unmanageable at first. However, living with MS and other common demyelinating disease does not have to be a terrible experience. There is promising new research about the causes of demyelination and how to treat the biological sources of myelin deterioration. Treatments are also being improved for the management of pain caused by demyelination.

Demyelinating diseases may not be curable. However, talking to your doctor about medications and other treatments may help you learn more about your condition. The more you know, the more you can address the symptoms by changing your lifestyle to confront the pain. When you can keep the symptoms of demyelination in check, you can feel peace of mind knowing how to control it.

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