This progressive condition is characterized by damage to motor and sensory nerves. Progressive muscle weakness is typically noticeable in adolescence or early adulthood, but CMT may differ between patients, even among relatives with the disorder. Symptoms usually affect the hands and arms after affecting the feet and legs.
This is one of the first signs of the disease in young children. They may have problems lifting their feet off the ground, and their toes may drop forward when they lift their feet (called foot drop).
These problems, as well as pes cavus (high arched feet), result from the loss of muscle bulk around the joints in the legs and feet, causing contractures. These are stiffened joints that tend to worsen over time, making it more difficult to walk.
Changes in the ability of muscles to contract may lead to tripping and frequent falls.
CMT can damage the cochlear nerve, the sensory nerve responsible for transmitting the electrical signals that enable hearing.
As such, a patient’s ability to hear is reduced, which usually occurs in both ears. Hearing loss can range from mild to severe in CMT, and patients usually have difficulty hearing mid- and high-frequency sounds.
According to the Inherited Neuropathies Consortium Natural History Study, around 15% of patients with CMT type 1 experience hearing loss, while this percentage is higher among those with CMT type 1B (28.2%) and CMT type 4 (30%). Some people with X-linked CMT and CMT type 2 may also have hearing loss.
This symptom may be present from infancy and worsen with disease progression.
The phrenic nerve, which controls the diaphragm muscle, can be affected by CMT. Breathing problems in CMT are usually not severe, but they can be life-threatening in rare cases.
Particularly in cases of CMT4 or CMT2, phrenic nerve abnormalities have led to half of the diaphragm not moving. The diaphragm is a dome-shaped muscle located below the lungs. It is the major muscle of respiration.
CMT patients may also develop sleep apnea, repeated pauses in breathing during sleep. This can be caused by obstructions in the upper airway (obstructive sleep apnea) or by changes in the signals sent by the brain to control breathing (central sleep apnea).
Patients who suspect they may have CMT-related breathing problems should talk to their physician about referring them to a cardiopulmonary specialist for a sleep study. Physicians can also perform a pulmonary function test, which measures how well the lungs work.
The uneven weakening of muscles also results in joints being pulled on unequally, which can eventually shift bones into abnormal positions and result in a condition called scoliosis.
Scoliosis is when the spine develops an abnormal sideways curvature. The severity of the curvature can vary from one patient to another, and may become progressively worse if not monitored and treated.
This condition can cause back pain in some patients and can make it more difficult to find clothes that fit well. Severe scoliosis can restrict the chest and impair lung function.
Scoliosis develops in more than a third of children with CMT and has been reported to have an average age of around 13 at diagnosis.
Fatigue is a common symptom in CMT. It results from the greater energy it takes to compensate for weakened muscles in walking, standing, and doing everyday activities. Sleep issues experienced by the CMT patient population are also a significant contributor to fatigue.
Strategies to manage fatigue include eating energy-sustaining stacks, regular exercise, getting proper sleep, reducing stress, and cognitive behavioral therapy.
People with CMT may experience tingling and burning sensations in their hands and feet, causing discomfort and sometimes pain. Their sense of touch and the ability to sense temperature changes are diminished. Some people with sensory loss have dry skin and hair loss in the affected area. In rare cases, patients may also develop tremor (uncontrollable shaking).
Some patients can have paralysis in their vocal cords, which usually is more problematic in children than in adults.
Last updated: Dec. 1, 2021
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