What is demyelination? 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. 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

an axon The axon sends messages from one neuron to the next. Axons also connect 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 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 medical conditions 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

thinking clearly

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 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-Barré syndrome (GBS), myelin may only be under attack for a few hours before symptoms appear. Early symptoms of demyelination Not everyone is affected by demyelinating conditions in the same way. However, some demyelinating symptoms are very common. Early symptoms — which are among the first signs of demyelination — include: loss of vision

bladder or bowel problems

unusual nerve pain

overall fatigue Symptoms associated with the effect of demyelination on nerves Nerves are a key part of your body functions, so 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 Symptoms can come and go in chronic conditions, like multiple sclerosis (MS), and progress over years.

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 leukoencephalopathy (PML). PML is caused by the JC virus. Myelin damage can also occur with: alcoholism

liver damage

electrolyte imbalances Hypoxic-ischemic demyelination occurs due to vascular disease or a lack of oxygen in the brain.

Demyelination and multiple sclerosis MS is the most common demyelinating condition. 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: clinically isolated syndrome

relapsing-remitting MS

primary progressive MS

secondary progressive MS

Treatment and diagnosis There’s no cure for demyelinating conditions, but new myelin growth can occur in areas of damage. However, it’s often thinner and not as effective. Researchers are looking into ways to increase the body’s ability to grow new myelin. Most treatments for demyelinating conditions reduce the immune response. Treatment involves using drugs like interferon beta-1a or glatiramer acetate. People with low vitamin D levels more easily develop MS or other demyelinating conditions. High levels of vitamin D may reduce inflammatory immune responses. Demyelination MRI 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. Your healthcare provider may be able to locate plaques or lesions affecting your nervous system. Treatment can then be directed specifically at the source of demyelination in your body. 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’re not likely to affect your CNS cholesterol. Many studies have also found that statin treatment may protect against Alzheimer’s disease (AD) in people who haven’t 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 don’t affect the CNS or remyelination, and still others say they do. Currently, most of the evidence doesn’t show statin therapy to be harmful to remyelination within the CNS. Still, the effects of statins on cognitive function remain controversial at this time.

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 71 documented cases from 1979 to 2014, and it’s not certain that vaccines were the cause of the demyelination.