What is Charcot-Marie-Tooth disease?
Charcot-Marie-Tooth (CMT) disease is a genetic condition that affects the peripheral nerves. These nerves connect the spinal cord to the muscles and sensory receptors in the body. They control muscle movement and help relay sensory information, such as touch, temperature and pain, back to the brain. In people with CMT, the nerves become weakened or damaged, leading to muscle wasting, loss of sensation and challenges with balance and coordination.
What is the anatomy of peripheral nerves?
Peripheral nerves consist of bundles of nerve fibres that transmit signals between the brain, spinal cord and the rest of the body. These nerves are primarily categorized into:
- Motor nerves: These carry signals from the brain to the muscles. They control voluntary movements such as walking or grasping objects.
- Sensory nerves: These carry information about sensations, such as touch, temperature and pain, from the skin and other parts of the body to the brain.
Peripheral nerves are protected by a myelin sheath, which is needed for efficient signal transmission. In CMT, damage can occur either to the myelin sheath (demyelinating forms) or the nerve fibers themselves (axonal forms), impairing the nerve’s ability to transmit signals.
What are the symptoms of CMT?
People with CMT experience a range of symptoms due to progressive damage to the peripheral nerves. Symptoms usually start in the feet and legs, and over time, the disease may also affect the hands and arms.
Symptoms vary widely depending on the specific type of CMT and it may also vary from person to person. CMT can appear at any age, though symptoms often begin in childhood or adolescence.
Most common symptoms include:
- weakness in the foot and lower leg muscles
- foot deformities, including high arches and hammertoes (curled toes)
- difficulty lifting the foot while walking (foot drop), causing stumbling and unsteady steps
- muscle loss in the hands and feet, making fine motor tasks such as buttoning clothing challenging
- numbness, tingling, burning or loss of temperature sensation in the hands and feet
- discomfort or pain in the hands and feet
- balance difficulties, leading to clumsiness and trouble navigating stairs
- muscle cramps, particularly in the legs
What causes CMT?
CMT is caused by genetic mutations that affect either the nerve itself (axon) or the protective myelin sheath surrounding the nerve. Damage to either of these parts disrupts the nerve's ability to send signals effectively, leading to the symptoms of CMT. There are over 80 known genetic causes of CMT, with each type of CMT depending on the specific gene affected. While most cases are inherited (passed down from one or both parents), some mutations can occur spontaneously in a child’s genes before birth.
How is CMT diagnosed?
A neurologist, a specialist in nerve and muscle disorders, may diagnose CMT by performing a thorough nervous system examination and asking about family history. To confirm CMT and rule out other treatable conditions, doctors use several diagnostic tests, including:
- Genetic testing: A blood or saliva test to detect gene mutations that cause CMT. Identifying the specific mutation helps doctors provide guidance on what patients and families can expect, and family members can also be tested to see if they carry the mutation.
- Nerve conduction velocity (NCV) testing and electromyography (EMG): These tests assess how well nerves and muscles are functioning. NCV measures the speed and strength of electrical signals travelling through the nerves. EMG checks how effectively the nerves communicate with the muscles, helping to pinpoint the cause of muscle weakness.
How is Charcot-Marie-Tooth disease treated?
There is currently no cure for CMT, but several treatments can help manage symptoms and improve quality of life. The main goal of treatment is to help children stay active and maintain independence. Treatments include:
- Physical therapy (PT): Exercises to strengthen and stretch muscles can help preserve flexibility and prevent deformities caused by weakness. Regular PT can also support balance and mobility.
- Occupational therapy (OT): OT assists with daily tasks at home, school or work by introducing adaptive techniques or devices, such as rubber grips for utensils or switching buttons and zippers to Velcro.
- Orthopedic devices: Braces, such as ankle-foot orthoses (AFOs), high-top shoes and thumb splints, provide support and make walking or handling objects easier.
- Pain management: Medications may be prescribed to alleviate pain associated with CMT.
- Surgical interventions: Surgery can be helpful in severe cases to correct foot deformities, release tight tendons or address other joint issues, such as scoliosis.
What are the complications of Charcot-Marie-Tooth (CMT) disease?
Charcot-Marie-Tooth (CMT) disease is not life-threatening, and most people with CMT have a normal lifespan and remain active. However, there are several possible complications:
- Injuries from falls: Muscle weakness and balance issues can increase the risk of falls, maybe leading to fractures or sprains.
- Breathing difficulties: In rare cases, CMT can affect the muscles used for breathing. This can be a problem when a person is sleeping. Some people may need a nighttime breathing device for assistance.
- Increased sensitivity to certain medications: Some medications, particularly neurotoxic drugs, can worsen CMT symptoms and should be avoided unless necessary.
- Injuries or infections in the feet: Due to reduced pain and temperature sensation, injuries or infections in the feet may go unnoticed. This may lead to complications if untreated.
- Joint stiffness and contractures: Progressive muscle weakness can lead to joint stiffness and contractures, especially in the ankles and hands. This may limit range of motion.
- Foot and hand deformities: Muscle imbalance can cause deformities such as high arches, hammertoes and claw-like hand positioning. These deformities may worsen over time and affect mobility or dexterity.
- Chronic pain: Some people with CMT experience chronic pain, either from nerve damage (neuropathic pain) or from muscle and joint stress.
- Scoliosis or spinal curvature: In some cases, CMT can lead to scoliosis or abnormal spinal curvature due to muscle weakness and imbalance.
Managing these complications typically involves a combination of physical therapy, assistive devices, regular monitoring and adaptations to maintain quality of life.
Genetic counselling
Genetic counselling can be a valuable resource. A genetic counsellor can provide support by explaining test results and helping families understand the implications of a CMT diagnosis. They can also discuss prenatal testing options if there is a family history of CMT or if a family member has tested positive for a CMT-related mutation. Genetic counselling can be especially useful in planning for future family decisions and managing the impact of CMT on family life.
Support
Connecting with others who have experience with CMT can provide a strong support network for families. Psychological counselling or participation in support groups can be beneficial both before and after a diagnosis, offering emotional support for children with CMT and their families. These resources help families navigate the challenges of CMT and provide a space for shared experiences and guidance
When to see a health-care provider?
Consult a health-care provider if your child shows signs of foot deformities, frequent falls or difficulty with activities involving hand strength.
Regular follow-up is recommended to monitor symptoms, address complications, and update care plans.
At SickKids
SickKids has a specialized neuromuscular clinic that focuses on CMT. Located within the neurology department, the clinic is staffed by a neurologist, nurse practitioner, and experienced technicians who are dedicated to caring for children with CMT. Our clinic visits range from simple follow-ups to more specialized procedures, such as nerve conduction studies and electromyography. Additionally, we offer access to a professional social worker who can provide support for both you and your child and connect you with relevant support groups if needed. You are not alone in this journey!
https://www.sickkids.ca/en/care-services/clinical-departments/neurology/neuromuscular-program/
Resources
Charcot-Marie-Tooth Association
cmtausa.org
Charcot-Marie-Tooth Disease (CMT) - Muscular Dystrophy Association
mda.org/disease/charcot-marie-tooth
References
Stojkovic T. (2016). Hereditary neuropathies: An update. Revue Neurologique, 172(12), 775-778. https://doi.org/10.1016/j.neurol.2016.06.007
Adam, M.P., Bick, S., Mirzaa, G.M., Pagon, R.A., Wallace, S.E., & Amemiya, A. (Eds.). (1993-2026). GeneReviews [Internet]. University of Washington. https://www.ncbi.nlm.nih.gov/books/NBK1116/
Szigeti K., & Lupski J.R. (2009). Charcot-Marie-Tooth disease. European Journal of Human Genetics, 17(6):703-10. https://doi.org/10.1038/ejhg.2009.31