What is Charcot-Marie-Tooth Disease?
Charcot-Marie-Tooth (CMT) disease is one of the most common inherited neurological disorders, affecting about 1 in 2,500 people in the United States and nearly 3 million people worldwide. The disease is named after the three physicians who first described it in the late 19th century: Jean-Martin Charcot and Pierre Marie in Paris, France, and Howard Henry Tooth in Cambridge, England.
CMT disease is also known as hereditary motor and sensory neuropathy (HMSN) or peroneal muscular atrophy and is part of a group of disorders called peripheral neuropathies, which affect peripheral nerves. The peripheral nerves supply the muscles and sensory organs in the limbs.
It takes a team to care for patients with CMT. The neurologists of Patient Centered Neurology at Mischer Neuroscience Associates have subspecialty training in peripheral neuromuscular diseases and electromyography (EMG), and focus on identifying CMT early, educating patients and monitoring their condition to avoid preventable complications. They work with physical and occupational therapists at TIRR Memorial Hermann Outpatient Rehabilitation, who help build strength and improve function, and with orthopedic surgeons specializing in foot and ankle disease. If CMT is diagnosed, genetic counseling is available to help individuals and families understand the condition and plan for the future.
Signs and Symptoms of CMT
A typical sign of CMT is weakness of the foot and lower leg muscles, which causes a high-stepping gait resulting in frequent tripping or falls. Foot deformities such as high arches or hammertoes are caused by weakness in the small muscles in the feet. Numbness, tingling and loss of feeling in the feet and legs are also signs of CMT.
As the disease progresses, weakness and muscle atrophy can occur in the hands, causing difficulty in the coordination with small movements in the fingers, hands and wrists. Symptoms often appear first in late adolescence or early adulthood but some people develop symptoms later in life. The severity of CMT differs from person to person – even within the same family – with difficulty in walking and running and neuropathic pain being the most common complications. Symptoms progress gradually, and some people need foot or leg braces or other orthopedic devices for mobility.
Causes of CMT
CMT is caused by mutations in genes that produce proteins involved in the structure and function of either the peripheral nerve axon, the part of a nerve cell that sends information to distant locations in the body, or the myelin sheath, which insulates the axon. Without an intact axon and myelin sheath, peripheral nerve calls are unable to activate muscles or send sensory information from the limbs back to the brain.
As the nerves slowly degenerate, the result is muscle weakness and atrophy in the legs, feet, arms and hands. The gene mutations in CMT disease are usually inherited. In rare cases the mutation causing CMT disease occurs spontaneously in an individual’s genetic material.
Neurologists who specialize in peripheral neuromuscular diseases start the diagnostic process with a standard medical history, family history and neurological examination. During the exam, the physician looks for evidence of muscle weakness in the arms, legs, hands and feet; a decrease in muscle tissue; reduced tendon reflexes; and loss of feeling in the limbs. Doctors also look for foot deformities, including high arches, hammertoes, inverted heels or flat feet.
If signs and symptoms are present, the doctor may conduct electrodiagnostic tests, including nerve conduction studies and EMG. Genetic testing is available for some types of CMT
and results are usually enough to confirm a diagnosis.
If the diagnostic testing is inconclusive or genetic testing comes back negative, the neurologist may perform a nerve biopsy to confirm the diagnosis. A nerve biopsy involves removing a small piece of peripheral nerve through an incision in the skin, usually in the calf of the leg.
Although there is no cure yet for CMT, a number of treatment options can help maintain muscle strength and improve independent functioning, including physical and occupational therapy, orthopedic equipment or orthopedic surgery in cases of severe foot deformities.
Physical and occupational therapy may strengthen muscles and delay or reduce muscle atrophy. Stretching may prevent or reduce joint deformities that result from
uneven muscle pull on bones. An exercise program that increases endurance may prevent fatigue, and moderate low- or no-impact aerobic activity can help maintain fitness
and overall health.
Many patients with CMT require ankle braces and other orthopedic devices to maintain mobility and prevent injury. Assistive devices can be used to prevent muscle
strain and reduce muscle weakening.
The CMT Association is a fantastic resource for families living with CMT. Through the CMT Association, you can access educational newsletters, webinars and
conferences, and stay apprised of important research updates. There are also opportunities to personally connect with other CMT families locally, regionally and nationally. Visit cmtausa.org to learn more.
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