Health Library

What Is Charcot-Marie-Tooth Disease (CMT)?

Charcot-Marie-Tooth disease (CMT) is an inherited neurological disorder. It affects the peripheral nerves (nerves outside the brain and spinal cord), causing muscle weakness and numbness.

CMT happens because of problems with motor nerves (which control muscles) and sensory nerves (which send sensations to the brain).

What Are the Signs & Symptoms of Charcot-Marie-Tooth Disease (CMT)?

There are many different types of CMT. Symptoms and the age when they begin depend on the type. In some types of CMT, babies and toddlers have weakness and muscle loss. They may:

• hold their head up, sit, crawl, stand, and walk later than most kids do
• fall more than brothers, sisters, or playmates of the same age
• have trouble grasping or holding items

In the most common forms of Charcot (shahr-KOE)-Marie-Tooth disease, symptoms first appear in teenagers or young adults. Symptoms all relate to muscle weakness or numbness in the hands, forearms, lower legs, and feet, and include:

• cold hands and feet
• trouble buttoning clothing and holding small items such as coins
• stumbling or unsteady steps, which may look like clumsiness
• dragging the feet or toes while walking (foot drop)
• trouble going up or down steps
• shuffling or marching steps
• feet with high arches and toes that stay curled (hammertoes)
• loss of feeling in the feet or legs
• trouble with balance

What Causes Charcot-Marie-Tooth Disease (CMT)?

Sensory nerves let us feel pain, pressure, touch, temperature, body position, and other feelings. Motor nerves tell muscles to move and how fast. To send strong and fast signals over long distances, nerves have to be wrapped in insulation called myelin. If the insulation doesn’t work well, the nerve can’t either.

CMT happens because of a mutation or variation (a change) in a person’s gene (DNA). A variation in one of the CMT-related genes can cause a problem with a protein that the body needs for nerves to work properly.

CMT mutations cause both sensory nerves and motor nerves to lose their ability to send signals. Some CMT mutations affect the nerve cells and others affect the cells that wrap the nerve in myelin. Without motor signals, muscles get smaller and weaker. Without sensory signals, children have trouble balancing, walking, and handling small items like buttons.

Who Gets Charcot-Marie-Tooth Disease (CMT)?

Many genes can cause CMT if they don’t work properly. The type of CMT depends on what gene is affected.

Sometimes, the parents’ DNA is normal and the CMT variation happens when the child’s DNA is forming. This is called a new or spontaneous mutation.

How Is Charcot-Marie-Tooth Disease (CMT) Diagnosed?

Doctors will do an exam, ask about symptoms, and find out whether family members have CMT or similar symptoms.

Tests can help make sure the problem is CMT and not something that could go away with treatment. These tests include:

• Genetic testing: This checks the child’s DNA for known CMT mutations. Knowing the kind of mutation helps doctors tell the patient and family what to expect. Family members also can be tested to see if they have the mutation.
• Nerve conduction velocity (NCV) testing and electromyography (EMG): These check nerves and muscles to find the cause of weakness and see if there is peripheral

  neuropathy
  .

How Is Charcot-Marie-Tooth Disease (CMT) Treated?

There is no cure for CMT disease yet. The treatment goal is to help the child stay as active as possible. Because of the loss of feeling, avoiding injury from impact and burns requires extra care.

Treatments to help children stay as active as possible include:

• Braces, such as ankle-foot orthoses (AFOs), to support the feet for easier walking.
• Medicines for pain relief.
• Physical therapy (PT) exercises and stretching to help maintain strength and flexibility.
• Occupational therapy (OT) to help with managing tasks at home, school, and work.
• Surgery to loosen tight tendons and joints (contractures).

Doctors will also check for other problems that are rare in CMT disease, like trouble with breathing during sleep.

Looking Ahead

Often, CMT symptoms are not severe, and many treatments can help. People with CMT have a normal life expectancy, and most can walk their entire lives. Support groups can help you and your child — they can connect you to other families who are managing CMT and keep you up to date on treatment research.