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Charcot-Marie-Tooth

Quick Facts

• ...is the most common inherited neuropathy, affecting approximately 125,000 Americans.
• ...is also known as peroneal muscular atrophy and hereditary motor sensory neuropathy.
• ...is slowly progressive, causing deterioration of peripheral nerves which control sensory information and muscle function of the hand/forearm.
• ...causes degeneration of peroneal muscles (located on the front of the leg below the knees).
• ...causes foot-drop walking gait, foot bone abnormalities, high arches and hammer toes, problems with balance, problems with hand function, occasional lower leg and forearm muscle cramping, loss of some normal reflexes, and scoliosis (curvature of the spine) is sometimes present.
• ...does not affect life expectancy.
• ...has no effective treatment, although physical therapy, occupational therapy and moderate physical activity are beneficial.
• ...is sometimes surgically treated.
• ...is usually inherited in an autosomal dominant pattern.
• ...may become worse if certain neurotoxic drugs are taken.
• ...can vary greatly in severity, even within the same family.
• ...can, in rare instances, cause severe disability.
• ...is the focus of significant genetic research, bringing us closer to answering the CMT enigma.

CMT types 1A, 1B, 1D, 2E, 2F, X-Linked, and HNPP can now be diagnosed by a blood test.

Charcot-Marie-Tooth, or CMT, is the most common inherited neurological disorder, affecting approximately 150,000 Americans. CMT is found world-wide in all races and ethnic groups. It was discovered in 1886 by three physicians, Jean-Marie-Charcot, Pierre Marie, and Howard Henry Tooth.

CMT patients slowly lose normal use of their feet/legs and hands/arms as nerves to the extremities degenerate. The muscles in the extremities become weakened because of the loss of stimulation by the affected nerves.

Additionally, there is a loss of sensory nerve function. Unlike muscular dystrophy in which the defect is in the muscles, CMT is a disorder in which the defect is in the nerves that control the muscles.

What are its characteristics?
A high arched foot is one of the first signs of this disorder. As the disease progresses, structural foot deformities take place. The patient develops a pes cavus foot with hammer toes. Foot drop and ankle sprains are frequent manifestations. The progressive muscle wasting leads to problems with walking, running, and balance. To avoid tripping, patients with foot drop raise their knees unusually high resulting in high steppage gait. In some patients, muscle weakness may also occur in the upper legs. Flat foot is seen as well in patients with CMT.

Hand function also becomes affected because of progressive muscle atrophy, making fine manipulatory acts, like writing, difficult.

The loss of nerve function in the extremities also leads to sensory loss. The ability to distinguish hot and cold is diminished as well as the sense of touch.

CMT also can be inherited in a recessive or an X-linked pattern. The degree of severity can vary greatly from patient to patient, even within the same family. A child may or may not be more severely disabled than his/her parent.

How is it inherited?
CMT is generally inherited in an autosomal dominant pattern. This means that if one parent has the disease (either the father or the mother) there is a 50% chance of passing it on to each child.

CMT can also be inherited in recessive or an X-linked pattern. To determine the pattern of inheritance, each CMT patient should consult a genetic counselor, neurologist or other medical authority familiar with the disease.

How is it diagnosed?
Careful diagnosis of CMT involves clinical evaluation of muscle atrophy, testing of muscle and sensory responses, nerve condition and electromyographic (EMG) studies, as well as a thorough review of the patient's history. CMT types 1A and 1X can now be diagnosed by a DNA blood test. Some people who carry the CMT genetic trait show no apparent physical symptoms. The variation in degree of physical disability, together with a lack of physician awareness of CMT, has often led to misdiagnosis.

Today, the Charcot-Marie-Tooth Association is educating both medical specialists and patients about CMT.

How is it treated?
At present there is no cure for CMT, although physical therapy and moderate activity are often recommended to maintain muscle strength and endurance.

Custom shoes or shoe inserts (foot orthoses) will help to improve gait. Leg braces will prevent ankle sprains, improve gait, and reduce the amount of energy needed to walk. Corrective orthopedic foot surgery is available to help maintain mobility when medically indicated.

Splinting, specific exercises, adaptive devices and surgery can help maintain hand function.

These drugs are toxic to the peripheral nervous system and can be harmful to the CMT patient.

* A megadose is defined as ten or more times the recommended daily allowance.

Drug Interaction Warning
The November/December 1995 NAMI Advocate warned of a potentially fatal drug interaction. It involves selective serotonin reuptake inhibitor antidepressants such as Prozac, Zoloft, Paxil and Luvox. Apparently, a drug interaction between these antidepressants and dextromethorphan and/or pseudoephedrine, found in over-the-counter cold remedies, can cause excessive serotonergic activity. Signs of this "serotonin syndrome" include changes in mental status, hypertension, restlessness, myoclonus (sudden muscle contraction), hyperreflexia (accentuated reflexes), diaphoresis (profuse perspiration), shivering and tremor.

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Last modified: 01/30/07