Demyelination refers to damage to the myelin around nerves. Myelin coats many nerves in the body, but it can become damaged due to inflammation from viral infections, autoimmune diseases, and other causes.

Nerves send and receive messages from every part of your body and process them in your brain. They allow you to:

  • speak
  • see
  • feel
  • think

Many nerves are coated in myelin, a fatty tissue that helps protect them and help them work properly. When it’s worn away or damaged, nerves can deteriorate, causing problems in the brain and body.

Damage to myelin around nerves is called demyelination. Demyelination can cause issues like:

  • numbness
  • weakness
  • vision changes
  • cognitive changes
  • behavioral changes
  • difficulties with movement

Keep reading to learn about demyelination, its types and causes, and how doctors diagnose and treat demyelinating diseases.

Myelin surrounds and protects parts of your nerves. It also supports their function.

Nerves

Nerves are made up of neurons. Neurons are composed of:

  • a cell body
  • dendrites
  • an axon

The axon sends messages from one neuron to the next and connects neurons to other cells, such as muscle cells.

Some axons are extremely short, while others are 3-feet long. 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 and covers an axon. This is similar to the idea of an electrical wire with a 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 0.5 to 10 meters per second, while in a myelinated neuron, it can travel up to 150 meters per second.

Certain medical conditions can damage myelin. Demyelination slows down messages sent along axons and causes the axon to deteriorate.

The location of the damage affects the symptoms a person experiences from demyelination.

Demyelination slows nerves’ ability to send messages. Symptoms can vary depending on which part or parts of the nervous system have damaged myelin.

For instance, demyelination of nerves in the lower spine may affect leg movement or bladder and bowel control. In contrast, demyelination of the optic nerve can affect eyesight.

The symptoms of demyelination may include:

How fast these symptoms can develop can depend on the cause of demyelination.

In some chronic conditions, like multiple sclerosis (MS), demyelination progresses over years. In relapsing-remitting MS, symptoms may worsen during flare-ups due to inflammation but then improve during periods of remission.

With other causes of demyelination, like Guillain-Barré syndrome, the demyelination process may occur much quicker, with symptoms appearing and worsening over hours.

Inflammation in the brain, spinal cord, or peripheral nerves can damage myelin. Inflammation can develop as part of the body’s response to infection. In the case of MS and other autoimmune causes, the immune system can mistakenly target and damage myelin.

Certain viruses can also directly damage myelin.

Other health conditions, including nutrient deficiencies and exposures to toxins, can also cause demyelination.

Demyelinating diseases of the brain and spinal cord

Some types of demyelination result from inflammation in the brain and spinal cord. These can include:

Multiple sclerosis (MS)

MS is a progressive autoimmune disease that causes demyelination in the brain, spine, or optic nerve. The immune system damages myelin, forming lesions or “plaques”. Over the years, many of these plaques or scar tissue occur throughout the brain, leading to increasing disability.

The types of MS include:

Learn about the possible causes of MS.

Transverse myelitis

Transverse myelitis results from inflammation in the spinal cord that can cause muscle weakness and paralysis. Transverse myelitis typically results from an infection, such as:

But can also happen due to an immune system response. It can also be linked to MS and other autoimmune inflammatory disorders, like rheumatoid arthritis and systemic lupus erythematosus.

Other causes of brain and spinal cord demyelination

Other demyelinating diseases of the brain and spinal cord include:

Demyelinating disorders of the peripheral nerves

Other demyelinating disorders can damage the peripheral nerves. The peripheral nervous system is the part of the nervous system that branches out from but isn’t located in the brain and spinal cord.

These disorders can include:

Optic neuritis

Optic neuritis is inflammation of the optic nerve. Optic neuritis can cause eye pain and vision changes, such as:

  • blurry vision
  • poor color vision
  • vision loss

It has many potential causes, and sometimes, it develops without a known cause. Causes can include:

Guillain-Barré syndrome

Guillain-Barré syndrome is a rare autoimmune disorder in which the immune system damages healthy nerve cells in the peripheral nervous system (PNS). Symptoms can include:

  • weakness
  • loss of reflects
  • sensory deficits and pain

It typically develops after an infectious illness, such as the stomach flu (gastroenteritis).

There is also a chronic form of Guillain-Barré syndrome, known as chronic inflammatory demyelinating polyneuropathy.

Other causes of demyelination

Nutrient deficiencies that can lead to demyelination can include:

  • vitamin B12 deficiency
  • copper deficiency
  • electrolyte imbalances

Demyelination can also result from exposure to toxins. Hypoxic-ischemic demyelination occurs due to vascular disease or a lack of oxygen in the brain.

Vaccines and demyelination: Is there a link?

Activating the immune system with a vaccine can potentially trigger an autoimmune reaction. This tends to occur only in a few individuals with hypersensitive immune systems. A virus, rather than a vaccine, is more likely to trigger a demyelination syndrome.

However, some children and adults have experienced “acute demyelinating syndromes” after exposure to certain vaccines, such as those for influenza or HPV. Researchers have documented71 cases of acute demyelination syndromes from 1979 to 2014, though it’s not certain that the vaccines caused the demyelination.

A 2021 review of research reviewed cases of acute demyelinating syndromes following COVID-19 vaccination and found 32 cases. More than half of these occurred in people with a history of immune-mediated disease.

Doctors typically diagnose demyelinating diseases and disorders after clinical examinations, lab tests, and imaging tests. Diagnosis typically involves ruling out other causes of neurological symptoms.

A doctor may order:

Demyelinating conditions, especially MS and optic neuritis, or 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.

Learn more about how doctors diagnose multiple sclerosis, the most common cause of demyelination.

There’s no cure for demyelinating conditions, but new myelin growth can occur in areas of damage, though it’s often thinner and less effective.

Current research is investigating ways to increase the body’s ability to grow new myelin, such as using drugs approved for other purposes and ways to manipulate cells to increase myelin regrowth after damage.

While the research looks promising, no currently applicable therapies are ready for use in people with demyelinating diseases.

If you’re diagnosed with a specific demyelinating disease, treatment may involve drugs prescribed to reduce damage, slow disease progression, and help manage symptoms.

Demyelination occurs when the myelin that surrounds nerve cells is damaged. This can affect the speed and ease at which nerve cells send messages.

Myelin also protects parts of nerve cells, and damage to it can leave the axon in the nerve cell vulnerable to deterioration.

Demyelination usually results from autoimmune diseases like MS and infections that cause inflammation to the brain, spinal cord, optic nerve, or peripheral nervous system. The location and severity of the damage usually determine the symptoms a person experiences.

There’s currently no cure for demyelinating disease or a way to repair the damage to the myelin. Research is focused on developing treatments to prevent myelin damage and promote regrowth.