Charcot-Marie-Tooth disease (CMT)

The nervous system in your body consists of the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system is made up of your brain and spinal cord. The peripheral nervous system is made up of nerves that carry messages from your brain and spinal cord to other parts of your body. 

The peripheral nerves have motor and sensory nerves. Motor nerves carry messages from your brain and spinal cord to your muscles, telling them to contract. Sensory nerves carry stimuli such as touch and pain in the form of signals to your brain and spinal cord. 

Image credit: 123rf

A peripheral nerve's structure can be seen in the image above. The axon is similar to the wiring of an electric cable that transmits messages between our brain and spinal cord and the rest of your body. The myelin sheath wraps around the axon and acts as a protection layer, similar to the insulation of a cable, to make sure electrical messages are not broken while they are being sent.

In CMT, the myelin sheath and axon of peripheral nerves are damaged. This is due to faulty genes. There are many different types of CMT that are caused by different faulty changes in your genes. The main types of CMT include:

• CMT 1
• CMT 2
• CMT 3
• CMT 4
• CMT X.

Read more about the types and classification of CMT(external link)(external link).

If you have CMT, you may have inherited faulty genes from one or both of your parents. 

The symptoms of CMT are different for each person and depend on the types of CMT. As it is a progressive condition (symptoms get worse over time), it is sometimes difficult to spot symptoms and diagnose a child with CMT. 

Early symptoms of CMT in children include:

• clumsiness
• walking difficulty
• foot drop
• difficulty lifting their feet up from the ground.

Symptoms usually start to appear between the ages of 5–15 years old.

Common symptoms of CMT include:

• high-arched feet (also called pes cavus)
• flat feet
• hammertoes or curled toes (middle joint of the toe bends upwards)
• muscle weakness in the lower legs (feet, ankles and legs) at first
• muscle wasting in the lower legs leading to an 'inverted champagne bottle' appearance
• foot drop causing them to lift their knees higher to walk to avoid trips (also called high stepping gait)
• walking difficulty
• loss of sensation in arms and feet
• cold hands and feet
• muscle and joint pain
• tiredness and fatigue. 

As symptoms get worse, it starts to affect your hands and arms more. It then causes problems with daily activities such as buttoning your shirt. Sometimes, damaged nerves can also cause shooting or burning nerve pain, which is also known as neuropathic pain. 

Your GP or doctor will ask questions related to your symptoms, including when your symptoms started and if you have any family history of CMT. Your GP will also examine your legs and arms and test your muscle movements. 

If your GP thinks you may have CMT, you will be referred to a neurologist (a doctor who specialises in nervous system conditions) for further testing and treatment. 

Tests or investigations you may have include the following:

• nerve conduction test – this is to test the strength and speed of electrical signals or messages transmitted through your nerves. The signals will be weak and slow in CMT.
• electromyography (EMG) – this measures the electrical activity in your muscles. 
• genetic testing – your blood samples will be taken to test for faulty genes to confirm and find out which type of CMT you have. 
• nerve biopsy – a sample of your nerve is taken to find out changes in the shape of the nerve under the microscope. This is usually done under a local anaesthetic. 

If you have a family history of CMT and are planning for a baby, ask your doctor for a referral to a genetic counsellor or specialist for advice. A genetic counsellor or specialist can go through the decision-making process with you and explain the tests and options you may want during pregnancy. 

Read more about pregnancy screening tests and checks. 

There is no cure for CMT so treatment aims to reduce your symptoms and help you manage your daily activities. You may have a team of healthcare providers involved in your care such as a physiotherapist, an occupational therapist, a podiatrist, an orthotist, an orthopaedic surgeon, your GP and a neurologist. You may also need to attend regular follow-ups, depending on the severity of your condition. 

Treatment can be categorised to the following:

• self-care measures
• physiotherapy
• occupational therapy
• orthoses and walking aids
• pain control
• surgery. 

Physiotherapy 

Physiotherapy can help improve the symptoms of CMT and reduce the risk of muscle contractures. It can also help strengthen your muscles and help with posture and balance issues. Not all people with CMT have the same problem, so ask your physiotherapist for a personalised exercise programme. 

Occupational therapy

Occupational therapy helps to improve your daily functioning and activities, eg, dressing, cooking, writing, buttoning and other daily tasks that involve the movements of your arms and hands. 

Orthoses and walking aids

Orthoses are devices that are worn inside your shoes to help improve the strength of your legs and correct how you walk and deformities of your legs. There are different devices available. Ask your orthotist (a healthcare professional specialises in braces and splints) for one that is suitable for you. 

Pain control 

In CMT, there are 2 types of pain:

• Joint and muscle pain – this type of pain can be relieved by regular painkillers such as non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen.
• Neuropathic or nerve pain – regular painkillers don't usually work for nerve pain. Medicines that have been found to be more effective in relieving nerve pain include amitriptyline, nortriptyline, gabapentin, pregabalin or carbamazepine. 

If your pain doesn't respond to one option, your doctor may suggest changing to another or combining more than one medicine. Your doctor will start you on a low dose and gradually increase the dose until you notice an effect.

Surgery

Sometimes, surgery may be needed to correct serious deformities caused by CMT. Your neurologist or doctor will let you know whether you need surgery. 

Self-care measures include:

• having a good balanced diet and maintain a healthy weight to avoid unnecessary strain on your joint and muscle
• regularly cleaning, checking and taking good care of your feet as there is a higher chance of injury and infection when you have a loss of sensation of your feet
• avoiding too much alcohol, caffeine and nicotine
• avoiding medicines that can cause nerve damage – ask your pharmacist or GP for a list of medicines to avoid if you are unsure. 

Living with CMT can be difficult and challenging both physically and mentally. Talk through your feelings with your family and friends to get the support you need. 

CMT disease NZ(external link)(external link) is an online support group on Facebook for people who have been diagnosed with CMT to share experiences and knowledge about CMT. There is also a face-to-face CMT group that meets once a month in Christchurch. Phone 03 354 3943 or email info@mda.org.nz to find out more. 

Muscular Dystrophy NZ(external link) (Facebook page) provides services and support for people who are affected by neuromuscular condition.