CMT (Charcot Marie Tooth disease) is a set of inherited disorders that cause nerve damage. This damage is mainly in the arms and legs (peripheral nerves). Charcot-Marie-Tooth disease is also called genetic motor and sensory neuropathy.
CMT disease affects the peripheral nerves. Peripheral nerves carry movement and sensation signals between the brain, spinal cord, and the rest of the body. Symptoms usually begin during adolescence—foot problems may be the first symptoms, such as high arcs or hammertoes. As CMT progresses, the lower legs can become weak. Later on, the hands may also become weak.
Doctors diagnose this disease using a neurological exam, genetic tests, or nerve biopsies. So there is no cure. The condition can be so mild that you don’t realise you have it, or it can be severe enough to weaken you. Physical therapy, working therapy, braces and other devices, and in some cases, surgery can help.
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Symptoms of CMT Disease
Some types of MTC cause damage to the sheath (myelin sheath) surrounding nerve fibres. Other kinds of CMT directly damage nerve fibres. In both cases, damaged nerve fibres result in neuropathy. The nerves of the legs and arms, which are the longest, are affected first. Nerve fibres that create movement (called motor fibres) and nerve fibres that transmit sensation (called sensory fibres) are also affected. Therefore, CMT causes weakness and numbness that usually begins in the feet.
- In most communal types of CMT, symptoms usually start before age 20. They may include:
- Foot deformity (bow feet);
- Foot drop (inability to keep the foot horizontal);
- “Bumped” gait (feet hitting the ground when walking due to foot drop);
- Loss of muscle in the legs, leading to skinny calves;
- numbness in feet;
- Balance problems.
Later, similar symptoms can also appear on the arms and hands. Therefore, CMT rarely affects brain function.
Diagnosis of CMT Disease
A careful neurological evaluation by an expert in neuropathy, including complete family history, physical examination, and nerve conduction tests, with appropriate genetic testing, is the way to establish the diagnosis of CMT. A physical exam may show the following:
- Difficulty lifting the foot when hiking;
- Problem by dorsiflexion of the toes and ankles (movement up, away from the ground) and other activities of the feet;
- Reduced or absent deep tendon reflexes (such as the patellar reflex);
- Loss of muscle switch and atrophy (shrinking of muscles) in the feet and legs (and later the hands).
Genetic testing can provide the exact cause for most people with CMT.
Cause of Charcot Marie Tooth Disease (CMT)
Sensory nerves allow us to feel pain, pressure, tactile sensations, temperature, body posture, and other sensations. The motor nerves tell the muscles when to move and how fast. To send strong, fast signals over long distances, nerves must be wrapped in an insulating material called “myelin.” If the insulation doesn’t work well, the nerve can’t work well either.
Charcot-Marie-Tooth disease is caused by a mutation or alteration (change) in a person’s gene (DNA). A variation in one of the genes associated with Charcot-Marie-Tooth disease can lead to a problem with a protein that the body needs for nerves to work correctly.
Mutations related to Charcot-Marie-Tooth disease cause sensory and motor nerves to lose their ability to send signals. Some mutations in Charcot-Marie-Tooth disease affect nerve cells, and others affect the cells that wrap the nerve with myelin. Without motor signals, the muscles shrink and weaken. Children have trouble keeping their balance, walking, and manipulating small objects like buttons without sensory cues.
Treatments for CMT Disease
There are no known treatments that stop or slow the progression of CMT, but the ADSC is funding research to find these treatments. Physical therapy, occupational therapy, and physical activity can help maintain muscle strength and improve independent functioning. Orthopaedic equipment (such as braces, inserts, or orthopaedic shoes) can make walking easier. Orthopaedic surgery on the feet often maintains or even restores walking function.
The symptoms of Charcot-Marie-Tooth disease are usually not severe, and many treatments can help. People with Charcot-Marie-Tooth disease have an average life expectancy, and most retain the ability to walk for life.