Charcot-Marie-Tooth Disease

Definition

Charcot-Marie-Tooth disease (CMT) is a progressive motor and sensory neuropathy (nerve disorder) characterized by weakness and atrophy, primarily in the leg muscles. It also known as hereditary sensory motor neuropathy, and peroneal muscular atrophy (PMA).

Description

Charcot-Marie-Tooth disease is named for French neurologists Jean M. Charcot and Pierre Marie, and British neurologist Howard Tooth, who simultaneously described the disorder in 1866.

CMT is generally divided into two types, which are similar in symptoms but different in respect to certain underlying nerve abnormalities.

The hypertrophic form, or Type 1, is characterized by thickened nerve fibers and abnormalities in their insulating material (myelin) and by slowed conduction of nerve signals along the fibers.

In the neuronal form, or Type 2, there is deterioration of the nerve fiber but little or no slowing of nerve impulses.

Causes and Risk Factors

Due to the slow progression of the disease, its onset is often difficult to determine. The hypertrophic form, which is the most common, usually manifests itself within the first 20 years of life, particularly during adolescence. The neuronal form of Charcot-Marie-Tooth disease normally appears after the age of 20.

There is usually an autosomal dominant mode of inheritance, but occasional cases occur on a sporadic basis (i.e., not inherited).

Symptoms

The disease is characterized by degeneration of the motor and sensory nerves that control movement and feeling in the arm below the elbow and in the leg below the knee. There is progressive muscle atrophy and wasting, resulting in severe weakness in the wrists, hands and fingers, as well as in the feet, ankles, and lower legs. Simple tasks requiring manual dexterity, such as buttoning buttons, picking up small objects and writing, may become difficult. In the legs, degenerative changes may limit mobility. Reflexes slow considerably.

Typically, CMT begins with weakness in the muscles of the feet, progressing to the calf muscles and the muscles in the lower arms.

Due to atrophy of muscles in the foot, the toes become cocked and the foot becomes fore-shortened and may develop a very high arch (pes cavus) or become uncommonly flat. Affected individuals develop a high-stepping drop-foot gait, with the foot raised well over the ground (stork leg), in order to prevent the forefeet from dragging on the ground and tripping them. The foot slaps as it hits the ground.

Affected individuals cannot run very fast, and due to weakness in the ankles, they often have frequent sprains. Changes in the shape of the foot may lead to blistering of the toes and other problems due to the unaccomodating shape of normal shoes. Loss of feeling occurs to a variable degree.

The disorder is slowly progressive, may stabilize for long periods of time, and may stop progressing entirely at any time. Therefore, affected individuals can never be sure about the extent of the ultimate severity of their condition. Lifespan is unaffected.

The severity of the disorder is highly variable, even among members of the same family. Some researchers believe a large number of mildly affected individuals are never diagnosed.

Diagnosis

Diagnosis is based on the medical history which includes symptoms and family history, the physical examination, and electrodiagnostic studies of nerve function.

Treatment

There is no known cure for Charcot-Marie-Tooth disease. However, physical therapists and orthopedists can treat the deformities and walking problems found in many people with the disorder. In addition, help and advice from an experienced podiatrist (foot doctor) may be valuable. Most of the therapy is focused on care of the feet and lower legs to ease mobility and to reduce problems caused by weakening and degenerative changes in the feet.

Surgery may also be helpful in some cases.

Questions to Ask Your Doctor

Which type of Charcot-Marie-Tooth disease is it?

To what extent has it progressed?

What are the causes of the disease?

Will it be passed onto the children?

What are the treatment options?

Is surgery an option?

Will walking be improved?

Should a physical therapist or podiatrist be consulted?

What is the prognosis?