What is CMT?

Charcot-Marie-Tooth disease (CMT) is an umbrella term for a range of inherited genetic disorders that affect the peripheral nervous system.

CMT takes its name from the three doctors who first recognised the disorder in the late 1800s.  Jean-Martin Charcot, Pierre Marie from France and Howard Henry Tooth from the United Kingdom.

Other names for CMT include peroneal muscular atrophy, hereditary motor and sensory neuropathy, and progressive muscular atrophy.

There are at least 90 known subtypes of CMT.  CMT is the most common inherited disease of the peripheral nervous system, affecting about 1 in 2,500 people.

The peripheral nervous system controls our ability to move and feel parts of our body, such as our hands and feet. Disorders of the peripheral nerves – the nerves that travel from the spinal cord to the muscles – are known as ‘neuropathies’.

Effects of CMT

The effects of Charcot-Marie-Tooth disease can vary widely. Some people may be only slightly affected – for example, shoes providing extra ankle support may be enough to support weak muscles in the feet and legs. Other people may need walking aids like sticks. Some people may need to use a wheelchair. 

In people with CMT, the nerves of the arms and legs work less well than usual.  This usually develops gradually, leading to wasting (thinning) of the muscles that are served by those nerves.  The onset of symptoms usually occurs in childhood or during the teenage years. The legs are most usually affected first. Over time muscles become weaker and harder to control.

There is no cure for CMT, but supportive care can help limit its impact, and new therapies are being examined in clinical trials. 

People with CMT generally have normal learning abilities and a normal life expectancy.

Symptoms of CMT

Symptoms of CMT are progressive and can include:

• Weakness in the muscles of the hands and feet
• Weakness of the muscles around the ankle
• Weakness of the hands  
• High foot arches (this is known as ‘pes cavus’) and clawed toes
• High-stepping gait and ‘slapping’ of the feet on the floor while walking
• Muscle wasting in the legs and arms
• Poor balance and occasional falls
• Loss of sensation, such as reduced ability to feel pain in the feet and hands  
  

Diagnosis of CMT

CMT is usually diagnosed through several tests including:

• Physical examination – strength testing and assessment of reflexes and sensation.  Common findings in CMT are loss of the muscle stretch reflexes (especially the ankle jerks), and weakness with lifting the feet (ankle dorsiflexion)
  
• Nerve conduction tests – used to determine which form of CMT is present
  
• Genetic tests – to identify the abnormal gene. CMT Type 1A, the most common form of CMT, can be diagnosed using a relatively routine test called a chromosomal microarray. Genetic testing for other types of CMT is less readily available, but may be done by gene panels. 

Treatment for CMT

While there is no cure for CMT, treatment can help manage some of the symptoms.

Options can include:

• regular stretching
• regular, moderate exercise involving low impact activities such as swimming or cycling
• physiotherapy
• occupational therapy
• orthotics
• orthopaedic surgery

Where to get help

Neurology Department, Royal Children’s Hospital Tel. (03) 9345 5661

Your local doctor

Charcot-Marie-Tooth Association of Australia (CMTAA) Tel. (02) 9767 5105

Things to remember

Charcot-Marie-Tooth disease (CMT) is the umbrella term for a range of inherited genetic disorders affecting the peripheral nervous system.

The way people are affected can vary widely. With supportive care, many people affected by CMT have minimal or no functional limitations.

People with CMT have normal learning abilities and a normal life expectancy.