Multiple Sclerosis and Other Demyelinating Diseases
What Is Demyelination?
- Myelin is an insulating material that, when it’s worn away or damaged, decreases nerve function. Damage to myelin is called demyelination.
- There are different types of demyelination. These include inflammatory demyelination and viral demyelination.
- MS is the most common demyelinating disease. In MS, demyelination occurs in the white matter of the brain and in the spinal cord.
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 that, when it’s worn away or damaged, decreases nerve function. Without myelin, nerves can deteriorate, causing problems in the brain and throughout the body. Damage to myelin around nerves is called demyelination.
Nerves are made up of neurons, 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 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.
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-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:
- Loss of reflexes and uncoordinated movements
- Poorly controlled blood pressure
- Blurred vision
- Racing heart beat or palpitations
- Memory Problems
- Loss of bladder and bowel control
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.
Types of Demyelination
There are different types of demyelination. These include inflammatory demyelination and viral demyelination.
Inflammatory demyelination happens when the body’s immune system attacks myelin. Types of demyelination like MS, optic neuritis, and acute-disseminated encephalomyelitis (ADEM) are caused by inflammation in the brain and spinal cord. Guillain-Barre syndrome (GBS) involves inflammatory demyelination of peripheral nerves in other parts of the body.
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.
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:
- Relapsing-remitting MS
- Primary progressive MS
- Secondary progressive MS
- Pprogressive relapsing MS
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. Research is underway to increase the body’s ability to grow new myelin.
Most treatments of demyelinating disease reduce the immune response using drugs like interferon beta or glatiramer acetate. Also, people with low levels of vitamin D more easily develop MS or demyelinating diseases, so high levels of vitamin D may reduce inflammatory immune response.
Demyelinating diseases, especially MS and optic neuritis (inflammation of the optic nerve), are detectable with MRI scans. MRI scans can often find 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