Demyelinating Diseases

In general, most of the nerves in your body are covered with a protective layer called myelin. It's a lot like the insulation on electric wires. Undamaged myelin allows messages from your brain move quickly and smoothly through your body, the way electricity flows from a power source.

Myelin sheaths cover many nerve fibers in the central and peripheral nervous system and they accelerate axonal transmission of neural impulses. Disorders that affect myelin interrupt nerve transmission.

Demyelinating disorders are any conditions that damage myelin. When damage occurs, scar tissue (sclerosis) forms in its place. Brain signals can't move through damaged nerves with scar tissue as quickly, so your nerves don't work as well as they should.

Myelin formed by oligodendroglia in the CNS differs chemically and immunologically from that formed by Schwann cells peripherally. Therefore, some myelin disorders (eg, Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, some other peripheral nerve polyneuropathies) tend to affect primarily the peripheral nerves, and others affect primarily the CNS (the brain, spinal cord, and optic nerves) are listed below.

Demyelination is often secondary to an infectious, ischemic, metabolic, or hereditary disorder or to a toxin (eg, alcohol, ethambutol). In primary demyelinating disorders, cause is unknown, but an autoimmune mechanism is suspected because the disorder sometimes follows a viral infection or viral vaccination.

Demyelination tends to be segmental or patchy, affecting multiple areas simultaneously or sequentially. Remyelination often occurs, with repair, regeneration, and complete recovery of neural function. However, extensive myelin loss is usually followed by axonal degeneration and often cell body degeneration; both may be irreversible.

Symptoms may reflect deficits in any part of the nervous system.

Symptoms

The most common symptoms of demyelinating disorders are:

•	Vision loss
•	Muscle weakness
•	Muscle stiffness
•	Muscle spasms
•	Changes in how well your bladder and bowels work

Causes

The causes of most conditions are usually unknown, but some result from:

•	A virus
•	Autoimmune condition - Inflammation from an immune response that goes awry and causes your body to attack its own tissues.
•	Your genes
•	Damage to blood vessels in your brain
•	Lack of oxygen to the brain

Treatment

There's no cure for these conditions, so early treatment is important. Treatment can help:

•	Lessen the effects of the attack
•	Control the disease course
•	Manage your symptoms

Medications can ease your pain, fatigue, and stiff muscles. Physical therapy can help with muscles that don’t work the way they used to.

Types of Demyelinating Diseases

Multiple Sclerosis (MS)

Multiple sclerosis (MS) is the most common demyelinating disease of the central nervous system (CNS). It's an autoimmune condition that attacks your brain, spinal cord, and optic nerve. In this disorder, your immune system attacks the myelin sheath or the cells that produce and maintain it.

This causes inflammation and injury to the sheath and ultimately to the nerve fibers that it surrounds. The process can result in multiple areas of scarring (sclerosis).

The most common symptoms are:

•	Extreme fatigue
•	Vision problems
•	Trouble moving
•	Tingling, burning, or other odd feelings

There’s no cure, but there are medications to change the course and lower the number of relapses. Plus there are many treatments and techniques to keep your symptoms in check.

Acute Disseminated Encephalomyelitis (ADEM)

Children are more likely to get this brief but widespread bout of inflammation that damages myelin in the brain and spinal cord. Sometimes it affects the optic nerve, which connects your eye to your brain. You get ADEM when your body attacks its own tissues in response to an infection with a virus or bacteria. It’s rare, but it can also be a reaction to a vaccine. Sometimes the cause is unknown.

Symptoms usually come on quickly. They include:

•	Fever
•	Low energy
•	Headache
•	Nausea and vomiting
•	Confusion
•	Irritation
•	Eyesight problems
•	Trouble with coordination

Drugs that fight inflammation a can stop the damage to the nerves in your brain and spinal cord. A doctor also can prescribe other medicine to ease some ADEM symptoms. Most people recover fully within 6 months, though in very rare cases, ADEM can be deadly.

Balo's Disease (Concentric Sclerosis)

Some doctors think of Balo's disease as a rare form of MS because the symptoms are the same in many ways. Experts don't know why people get it, but it can cause serious problems. It can be fatal, but it's possible to recover fully, too. Asians and people from the Philippines are the most likely to get it. It affects adults more often than children.

Symptoms might come on quickly and get worse in a short amount of time and then they might go away quickly. They include:

•	High fever
•	Headache
•	Trouble talking or understanding information
•	Memory loss
•	Muscle spasms
•	Seizures
•	Paralysis

There isn't a cure for Balo's disease, and no drugs treat it. Your doctor can suggest medications to help with your symptoms, including steroids to bring down the swelling in your brain and spinal cord.

Charcot-Marie-Tooth Disease (CMT)

It affects peripheral nerves that lie outside your brain and spinal cord and send signals to the muscles in your limbs. It's a condition you inherit from your parents when you’re born.

Symptoms usually show up in your late teens or early adult years. But they can come on in midlife, too. You may notice:

•	Weakness in your legs, ankles, and feet
•	Loss of muscle mass in your legs and feet
•	Trouble raising your legs and moving your ankles
•	Less feeling in your legs and feet
•	Changes to your feet, like higher arches or curled toes
•	Trouble walking or running
•	Tripping or falling

There's no cure, but your doctor will may give you medicines for pain. They should also suggest physical and occupational therapy to help you learn to use any affected limbs. Exercise can help you build stamina and keep muscles strong. Over time, you may need braces and splints for weak joints.

Guillain-Barre Syndrome (GBS)

Like CMT, this condition also attacks peripheral nerves. It often starts with weakness in your legs that moves to your arms and upper body. It can lead to paralysis. And it could be life-threatening if it causes trouble breathing. Doctors don’t know the cause, but it often follows a respiratory or digestive tract infection. Some people get it after surgery or a bout of the Zika virus. Most people reach maximum weakness within 2-3 weeks.

The most common symptoms include:

•	Tingling in your fingers, toes, ankles, or wrists
•	Weakness in your legs that spreads to your upper body
•	Trouble walking or climbing stairs
•	Bowel or bladder problems
•	Trouble moving your face, speaking, or chewing

There's no cure for GBS. Doctors try to lessen its effects with medication and speed up recovery. Plasma exchange (PLEX) is a common treatment. It removes some of the liquid part of your blood, called plasma, and replaces it with a manmade version. Another option is intravenous immunoglobulin (IVIG). The doctor puts proteins called immunoglobulins into your veins. They’re the same proteins your body uses to attack invaders, but they come from healthy donors. If the disease affects body functions like breathing, you’ll need treatment in a hospital. Caregivers may help move your limbs when you can’t to prevent clots. Later, you’ll get physical therapy to help you use your limbs again.

HTLV-I Associated Myelopathy (HAM)

This condition results from a virus called HTLV-1. It can make your brain and spinal cord swell, which causes the symptoms of the disease. Not everyone who has the virus will get HAM. Some people also carry HTLV-1 but have no symptoms.

People with HAM usually live near the equator. You get it by coming into contact with blood or other body fluids of someone who has the disease. It isn't usually fatal, but it can be. You might can live with the disease for decades.

Symptoms include:

•	Weakness in your legs that gets worse over time
•	Numbness or tingling
•	Stiff muscles
•	Muscle spasms
•	Bladder problems
•	Constipation
•	Double vision
•	Deafness
•	Coordination problems
•	Tremors

There isn't a cure, but steroids can help ease your symptoms.

Neuromyelitis Optica (Devic’s Disease)

This rare disease can affect your eyes, arms, and legs. Doctors don’t know what causes it, but they do know it makes your body attack your optic nerve and spinal cord. You may have blurred vision or lose your eyesight. If it’s in your spinal cord, your legs and arms might not work well.

If you have one attack of neuromyelitis optica, you’ll probably get another. But if your doctor catches the disease early, they will have a better chance of treating your symptoms. He may try drugs that turn down your immune system so you don’t have relapses.

Symptoms include:

•	Blurred vision
•	Loss of eyesight
•	Eye pain
•	Weak or numb arms and legs
•	Bladder and bowel problems
•	Vomiting
•	Uncontrollable hiccups

Neuromyelitis optica doesn't have a cure or FDA-approved medications to treat it. Your doctor may give you a steroid shot to help with swelling. He may also try a treatment called plasma exchange.

Drugs that suppress your immune system, like azathioprine, methotrexate, mycophenolate, and rituximab, can help prevent further attacks.

Schilder’s Disease

This rare condition most often affects boys between ages 7 and 12. It wears away myelin in the brain and spinal cord. Severe cases can affect breathing, heart rate, and blood pressure.

Doctors aren't sure what causes Schilder’s disease, but it usually starts with an infection. Often, a headache and fever are the first symptoms.

This disease is hard to predict. Some people will have flares of symptoms followed by times of recovery. For others, the disease slowly gets worse over time. Signs include:

•	Weakness on one side of the body
•	Slow movements
•	Seizures
•	Trouble speaking
•	Vision and hearing problems
•	Memory problems
•	Change in personality
•	Weight loss

There's no cure, but some people can manage their symptoms well with steroids and drugs that calm the immune system.

Transverse Myelitis

Transverse myelitis is an inflammation of your spinal cord. It results from damage to nerve cells in a certain area. This spinal cord disorder can cause symptoms throughout your body. It depends on the specific location of the spinal cord that myelin is lost.

The condition may show up as a symptom of neuromyelitis optica. It also makes you more likely to be diagnosed with MS later on. There are about 1,400 new cases of transverse myelitis each year.

It affects kids and adults, but women are more likely to get it than men. Doctors aren't sure about the cause, but it often follows an infection. Some people have long-lasting effects. Others recover with no problems.

Symptoms include:

•	Problems moving your legs
•	Bladder and bowel problems
•	Lower back pain
•	Muscle weakness
•	Sensitivity to touch
•	Tingling or numbness in your toes
•	Fatigue

There's no cure for transverse myelitis and no FDA-approved medication to treat it. Steroid shots or plasma exchange (PLEX) may bring down the swelling in your spinal cord and ease other symptoms.