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Charcot-Marie-Tooth disease

 

Charcot-Marie-Tooth disease (CMT), also known as hereditary motor and sensory neuropathy, is a group of inherited conditions that cause damage to the peripheral nerves (neuropathy).

The peripheral nerves are located outside the main central nervous system (the brain and spinal cord). They control the muscles and relay sensory information, such as the sense of touch, from the limbs to the brain.

People with CMT experience:

  • motor symptoms, such as muscle weakness, an awkward gait (the way that a person walks), and curled toes
  • sensory symptoms, such as numbness or pain

Symptoms of CMT usually begin during the teenage years or in early adulthood, although they can start at any time. CMT is a progressive condition, which means that the symptoms slowly get worse as the sensory and motor nerves deteriorate.

How common is CMT?

CMT is one of the most common inherited conditions that affect the peripheral nerves. It is estimated that in Europe, CMT affects up to 1 person in every 2,500.

Women and men are equally affected by CMT. The condition also affects people of all ethnic groups.

Outlook

CMT causes nerve damage that can lead to deformities in the limbs, such as:

  • flat feet
  • high foot arches
  • curvature of the spine (scoliosis)

CMT can also cause problems with manual dexterity. People living with the condition may have problems performing everyday tasks, such as opening cans, typing or picking up objects.

There is currently no cure for CMT. However, a range of treatments can help to relieve the symptoms, aid mobility and increase the independence and quality of life for people with the condition.

CMT is not life-threatening, and most people with the condition have the same life expectancy as a person who does not have CMT.

Central nervous system
This is made up of your brain and spinal cord.

Peripheral nerves
The network of nerves that run from the brain and spinal cord and carry impulses to and from the rest of the body, such as the limbs and organs are responsible for the body's senses and movements.

The severity of the symptoms of Charcot-Marie-Tooth disease (CMT) can differ from person to person, even among relatives with the condition. There are several different types of CMT. The symptoms of each type can also vary, even within the same type, as well as:

  • the age at which the symptoms first appear
  • how quickly the symptoms progress
  • how severe the symptoms are  

Early symptoms of CMT

CMT is a progressive condition, which means that the symptoms gradually get worse over time. Therefore, it may be difficult to spot any symptoms in children who have CMT.

Signs and symptoms that may indicate that a child has CMT include:

  • appearing unusually clumsy and accident-prone for their age
  • finding it difficult to walk because they may have problems lifting their feet from the ground
  • their toes drop forward as they lift up their feet

Common symptoms of CMT

The symptoms of CMT usually appear before a person is 20 years old. The symptoms may become more apparent after puberty (when a child becomes a sexually developed adult), and the body is fully developed. However, the symptoms of CMT can begin at any time, even when a person is in their 70s.

Common symptoms of CMT include:

  • muscle weakness in your feet, ankles and legs
  • having feet that are very highly arched, which can make your ankle unstable or, alternatively, you may have very flat feet
  • curled toes, which are often referred to as 'hammer toes'
  • difficulty using your ankle muscles to lift your foot up
  • an awkward or higher-than-normal step
  • a lack of sensation in your arms and feet

If you have CMT, you may also develop a distinctive leg shape, which resembles an upside-down champagne bottle. Your thigh muscles will usually retain a normal shape and muscle bulk, but the section of leg below the knee may become very thin.

Symptoms of progressive CMT

As CMT progresses, the muscle weakness and lack of sensation will begin to affect your hands and arms. This can lead to problems with both manual dexterity and hand strength, making tasks such as doing up the buttons of a shirt difficult or, in some cases, impossible.

Problems with walking and posture can put excessive strain on your body, which leads to muscle and joint pain. Less commonly, the damaged nerves may also cause pain, known as neuropathic pain.

Problems with mobility and walking tend to get worse as you get older. Older people with CMT are more likely to need a walking aid to get around.

In order to understand the causes of Charcot-Marie-Tooth disease (CMT), it is useful to first understand how the peripheral nerves work.

The peripheral nerves

The peripheral nerves are a network of nerves that run from the brain and spinal cord (the central nervous system) and carry impulses to and from the rest of the body, such as the limbs and organs. Peripheral nerves are responsible for the body's senses and movements.

A peripheral nerve is similar to an electrical cable, which is made up of two parts: the axon and the myelin sheath.

  • The axon is like the wiring in an electrical cable. It is the part of the nerve that transmits the electrical information between your brain and limbs.
  • The myelin sheath acts like the insulation of an electrical cable. It is wrapped around the axon to protect it and ensure that the electrical signal does not get broken up.

Damage to the nerves

In some types of CMT, faulty genes (units of genetic material) cause the myelin sheath to disintegrate. Without the protection of the myelin sheath, the axons become damaged, and the muscles and senses no longer receive the proper messages from the brain. This leads to the muscle weakness and numbness.

In other types of CMT, the axons are directly affected. Due to faulty genes, the axons do not transmit the electrical signals at the proper strength, which means that the muscles and senses are under-stimulated. Again, this leads to the symptoms of muscle weakness and numbness.

The genetics of CMT

CMT is an inherited (genetic) disorder, which is caused by mutated (changed) genes that you inherit from your parents. The genes involved produce the proteins that affect either the axon of the peripheral nerve, or the myelin sheath.

There is no single mutated gene that causes CMT. The many varieties of CMT are caused by different genetic mutations.

CMT is an unusual genetic disorder because the mutated genes can be inherited in several different ways. These ways are described below.

Autosomal dominant

Autosomal dominant inheritance of CMT occurs when one copy of a mutated gene is enough to cause the condition. If either parent carries a defective gene, there is a 1-in-2 chance that the condition will be passed on to any children that they have.

Autosomal recessive

Autosomal recessive inheritance of CMT occurs when two copies of the defective gene are needed to cause the condition. You inherit one copy from each parent. As your parents have only one copy of the gene, they do not develop CMT themselves.

If both you and your partner are carriers of the autosomal recessive CMT gene:

  • there is a 1-in-4 chance that your child will develop CMT
  • there is a 1-in-2 chance that they will inherit one of the defective genes and become a carrier (although they will not have any of the symptoms of CMT)
  • there is a 1-in-4 chance that they will receive a pair of healthy genes

If only you have the autosomal recessive gene, and your partner does not, your child will not develop CMT. However, there is a 1-in-2 chance that your child will carry the defective gene.

X-linked inheritance

In X-linked inheritance, the mutated gene is located on the X chromosome and is passed from a mother to her child. Chromosomes are the sections of your body's cells that carry your genes.

Men have XY sex chromosomes. They receive the X chromosome from their mother and the Y chromosome from their father. Women have XX sex chromosomes. They receive one X chromosome from their mother and the other X chromosome from their father.

A woman with the defective X chromosome (a female carrier) may have none or mild symptoms because the other healthy X chromosome may counter the effect of the defective one. However, some women may be as severely affected as men.There is a 50% chance that a female carrier will pass on the defective gene to her son who will then be affected with CMT.

If a female carrier passes on the defective gene to her daughter, the daughter may have no symptoms or be mildy affected or may be as severly affected as a male. However even if the daughter does not have symptoms, she may pass the gene onto her children and therefore CMT may appear to skip a generation. If a woman with the defective X chromosome only has daughters, CMT can skip a generation until one of her grandsons inherits it.

Other causes

As well as identifying the different genes that are involved in CMT, future research may also consider other factors that could affect the development of the condition.

Even among family members with the same type of CMT, symptoms can vary widely. It is therefore possible that other genetic or environmental factors affect the development of CMT.

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
Central nervous system
This is made up of your brain and spinal cord.
Chromosomes
Chromosomes are the parts of your body's cells that carry genes. A human cell usually has 23 pairs of chromosomes.
Gene
A gene is a unit of genetic material that determines your body's characteristics.
Genetic
Genetic is a term that refers to genes. Genes are the characteristics inherited from a family member.
Periphery nerves
The network of nerves that run from the brain and spinal cord and carry impulses to and from the rest of the body, such as the limbs and organs. They are responsible for the body's senses and movements.

Types of CMT

There are many different types of CMT, which are all caused by different mutations (changes) in your genes. More than 50 different genes are now known to cause CMT and many more are still unknown. The most common types of CMT are outlined below.

CMT 1

CMT 1 is caused by defective genes that are involved in the production of the myelin sheath. The defects cause the myelin sheath to slowly break down. CMT 1 is the most common type of CMT, accounting for around a third of cases.

CMT 2

CMT 2 is caused by defects in the axon. It is less common than CMT 1, accounting for around one in six cases.

CMT 3

CMT 3, also known as Dejerine-Sottas disease, is a rare and severe type of CMT that affects the myelin sheath. It is characterised by extreme muscle weakness and sensory problems. Unlike many other types of CMT, the symptoms usually begin in early childhood.

CMT 4

CMT 4 is another rare type of CMT that also affects the myelin sheath. As with CMT 3, the symptoms of CMT 4 usually begin in childhood, and many people with the condition are unable to walk.

CMT X

CMT X is a type of CMT that is caused by a mutation in the 'x' chromosome, which is one of the chromosomes that determine what sex you are. CMT X is more common in men than in women, and is estimated to account for around 1 in 10 CMT cases

Useful Links

During the initial stages of diagnosing Charcot-Marie-Tooth disease (CMT), your GP will ask you about your symptoms and whether there is any history of CMT in your family.

Your GP may want to know:

  • when your symptoms started
  • how severe your symptoms are
  • if anyone in your family has CMT

Physical examination

After asking you about your symptoms and family history, your GP will carry out a physical examination. During the examination, your GP will be looking for evidence of the condition, such as:

  • muscle weakness
  • reduced muscle tone
  • foot deformities, such as high arches or flat feet

Further tests

If CMT is suspected, you may be referred to a neurologist (a doctor who specialises in treating conditions of the nervous system) for further testing. Some of the tests you may have are described below.

Nerve conduction test

A nerve conduction test measures the strength and speed of the signals being transmitted through your periphery nerves (the network of nerves that run from the brain and spinal cord to and from the rest of the body, such as the limbs and organs).

Electrodes (small metal discs) are placed on your skin, which release a small electric shock that stimulates the nerves. The speed and strength of the nerve signal is then measured. An unusually slow or weak signal could indicate CMT.

Electromyography (EMG)

An electromyography (EMG) uses a small needle-shaped electrode which is placed in your skin to measure the electrical activity of your muscles. Some types of CMT cause a distinctive change in the pattern of electrical activity that can be detected by an EMG.

Nerve biopsy

A nerve biopsy is a minor surgical procedure where a tiny sample of a peripheral nerve is removed from your leg for testing. CMT can cause physical changes to the shape of the nerve, which can be seen under a microscope.

The biopsy is carried out under a local anaesthetic, so you will be awake but unable to feel any pain.

Genetic testing

Genetic testing involves taking a sample of your blood and testing it for the defective genes (units of genetic material) that are known to cause CMT. So far, over 50 of these genes have been found. However, there may be many more that have not yet been identified.

It is estimated that 70% of people with CMT may be able to have their diagnosis confirmed by genetic testing, and find out exactly which type of CMT they have. For others, genetic testing may prove inconclusive because an unidentified gene may be involved in their CMT.

Pre-natal testing

Pre-natal testing may help to determine whether an unborn baby has CMT. This may be useful if you or your partner has CMT, or if you know that you are carrying a gene that causes it, and you are going to become a parent.

There are two possible tests that might be used:

  • chorionic villus sampling (CVS)
  • amniocentesis

These tests are described briefly below.

Chorionic villus sampling (CVS)

Pre-natal testing for conditions such as CMT can be carried out around 10 to 12 weeks into the pregnancy using chorionic villus sampling (CVS).

CVS involves taking a small sample of cells from the placenta (the organ that links the mother's blood supply with her unborn baby's). The sample is tested for genetic (inherited) conditions.

Amniocentesis

Amniocentesis can also be used to test for CMT. This test is carried out around 15-18 weeks into the pregnancy. It involves taking a small sample of amniotic fluid (the fluid that surrounds the unborn baby in the womb) for examination.

Caution

It is important to remember that although these tests may help to determine whether your child has the defective gene, they will not indicate how serious the CMT will be. This is because the symptoms and the progression of the condition can vary widely, even among family members with the same type of CMT.

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
Central nervous system
This is made up of your brain and spinal cord.
Gene
A gene is a unit of genetic material that determines your body's characteristics.
Genetic
Genetic is a term that refers to genes. Genes are the characteristics inherited from a family member.
Peripheral nerves
The network of nerves that run from the brain and spinal cord and carry impulses to and from the rest of the body, such as the limbs and organs. They are responsible for the body's senses and movements.
Placenta
The organ that links a pregnant woman's blood supply to her unborn baby's.
Spinal cord
The spinal cord is a column of nervous tissue located in the spinal column. It sends messages between the brain and the rest of the body.
Uterus
The uterus (or womb) is a hollow, pear-shaped organ in a woman where a baby grows during pregnancy.

Treatment for Charcot-Marie-Tooth disease (CMT) is based on rehabilitation techniques to help you live with your symptoms, and surgery to correct any deformities in your bones, for example, in your feet.

As CMT is a progressive condition (it gets worse over time), you will need to be assessed regularly in order to check for any new developments in your condition. How often you are assessed will depend on the type of CMT that you have, and the severity of your symptoms. 

Your treatment programme may involve a number of healthcare professionals working together in a multidisciplinary team (MDT). You will usually have a doctor who co-ordinates your treatment programme and makes sure that every aspect of your condition is closely monitored and treated if necessary.

See the box (right) for some of the healthcare specialists that may be included in your MDT.

Physiotherapy

Physiotherapy is one of the most important treatment methods for relieving the symptoms of CMT and slowing the progression of the condition.

Physiotherapy, often referred to as physio, uses physical methods, such as massage and manipulation, to promote healing and wellbeing. It usually involves low-impact exercises such as:

  • stretching
  • swimming
  • moderate weight-training

Exercise 

There is a lack of good quality medical research into the benefits of exercise for people with CMT. However, it is possible that some types of exercise are beneficial. For example:

  • strengthening exercises, which focus on strength training, such as lifting weights, may help to improve muscle strength
  • aerobic exercise, which raises your heart rate and makes you breathe harder, such as walking or swimming, may improve your fitness and your ability to function on a day-to-day basis
  • posture and balance exercises, such as yoga, may also have benefits

Any exercise needs to be carefully planned as part of a personalised exercise programme. While a certain level of exercise may be safe, you risk making your symptoms worse if you do not follow proper instructions.

Speak to your GP or physiotherapist about arranging a suitable exercise programme.

Occupational therapy

Occupational therapy involves identifying problem areas in your everyday life, such as dressing yourself, then working out practical solutions.

Occupational therapy will be very useful if muscle weakness in your arms and hands makes it difficult for you to do day-to-day tasks, such as dressing or writing.

An occupational therapist will teach you how to use adaptive aids to compensate for your difficulties, such as clothing that has clasps instead of buttons, and magnetic tubes that allow you to pick up objects.

Orthoses

Orthoses are devices that are worn inside your shoes or on your legs to improve the strength and functionality of your limbs, or to correct your gait (the way you walk).

There are several different types of orthoses, including:

  • insoles in your shoes
  • custom-made shoes that support your ankles
  • ankle or leg braces
  • thumb splints that can improve your hand strength

Wheelchairs 

In the most severe cases, someone with CMT may require a wheelchair. However, it is estimated that a wheelchair is necessary for less than 1 in 20 people.

Pain management

There are two types of pain that are associated with CMT:

  • joint and muscle pain - caused by the stresses that CMT places on your body
  • neuropathic pain - caused by the damage to your nerves

Joint and muscle pain

Joint and muscle pain can usually be controlled by taking non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen.

Neuropathic pain

Neuropathic pain may be treated with medicines that are known as tricyclic antidepressants (TCAs). As the name suggests, TCAs were originally designed to treat depression, but they have also successfully treated some cases of neuropathic pain.

Common side effects of TCAs include:

  • dry mouth
  • constipation (being unable to empty your bowels)
  • sweating
  • problems passing urine
  • slight blurring of vision
  • drowsiness

These side effects should ease after 7 to 10 days as your body gets used to the medication. Do not smoke cannabis when taking TCAs because it may cause a rapid heart beat

Alternatively, you may be prescribed an anti-convulsant medicine (a medicine that is often used to prevent seizures), such as carbamazepine, gabapentin or pregabalin. These are often used to treat other conditions that cause neuropathy because they calm down nerve impulses and help to relieve pain.

In some cases, anti-convulsants can cause several side effects, such as:

  • drowsiness
  • dizziness
  • nausea (feeling sick)
  • vomiting

For full details of possible side effects, see the patient information leaflet that comes with your prescribed medication.

Lifestyle

The treatment of CMT aims to lessen the effect the condition has on your everyday life. However, there are precautions that you should take - for example, certain medicines may need to be avoided. You may be given the following advice:

  • avoid medicines that are known to cause nerve damage, such as vincristine (a medicine used to treat cancer)
  • avoid caffeine (found in tea, coffee and cola) and nicotine (found in tobacco) if you have tremors (shaking), as they can make this worse
  • avoid drinking too much alcohol as this has many health risks, which may be worse if you have CMT
  • avoid becoming obese (very overweight) because this can make walking more difficult

Ask your MDT if they have specific lifestyle recommendations for you, as the risks may vary from person to person. 

Surgery

If CMT causes significant deformities in your feet that cause you pain, surgery may be needed to correct them. There are three main surgical techniques for correcting deformities. They are:

  • osteotomy
  • arthodesis
  • plantar fascia release

These are described in more detail below.

Osteotomy

An osteotomy is a surgical procedure that is used to correct severe flatness of the feet. An incision (cut) is made in your foot and the surgeon removes or repositions the bones in your foot in order to correct its shape.

After surgery, your foot (or feet) will need to be kept in plaster for several weeks until the bones have healed.

Arthrodesis

Arthrodesis can also be used to correct flat feet, as well as relieve joint pain and correct heel deformities. It involves fusing the three main joints in the back of your feet in order to strengthen your feet, correct their shape and relieve pain.

After surgery, your foot (or feet) will be placed in a cast (a hard covering that is usually made of plaster), and you will not be able to place any weight on them for six weeks. During this time, you will need to use crutches or a wheelchair.

Once you can put weight on your feet, you will need to wear the cast for another six weeks (12 weeks in total). However, it may take up to 10 months for you to fully recover from the operation.

Plantar fascia release

Plantar fascia release is a surgical procedure that is used to relieve the persistent heel pain caused by inflamed (red and swollen) tendons. Tendons are the white, fibrous cords that join bones to muscle.

During the procedure, part of the tendon is removed and the remaining tendon is repositioned and allowed to heal. Afterwards, you will need to wear a cast for three weeks, and you will not be able to put any weight on your feet during this time.

Scoliosis

If you have curvature of the spine (scoliosis), you may need to wear a back brace to correct it. In more severe cases of scoliosis, surgery may be required.

Genetic counselling

If you or your partner has CMT and you want to have a child, you may be referred to a genetic counsellor.

A genetic counsellor is someone who specialises in helping people with genetic conditions who want to have children. They will be able to explain the exact risks of you passing CMT on to your child.

In some cases, it may be possible to test an unborn baby for CMT during the initial stages of pregnancy. If the test is positive, you will have to decide whether you wish to proceed with the pregnancy. The decision is for you and your partner to make. Nobody should pressure you into making a particular choice.

Research

There is some promising research that may provide new ways of treating people with CMT. This research includes:

  • using stem cells (cells that are at an early stage of development) to repair nerve damage
  • using hormones (powerful chemicals) and gene therapy to slow the progression of the condition

Ascorbic acid (vitamin C) is currently being tested in a number of clinical trials (medical research that tests one type of treatment against another). It is thought that ascorbic acid may improve the neuropathy (nerve damage) that is caused by CMT. 

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
Central nervous system
This is made up of your brain and spinal cord.
Gene
A gene is a unit of genetic material that determines your body's characteristics.
Genetic
Genetic is a term that refers to genes. Genes are the characteristics inherited from a family member.
Incision
An incision is a cut made in the body with a surgical instrument during an operation.
Peripheral nerves
The network of nerves that run from the brain and spinal cord and carry impulses to and from the rest of the body, such as the limbs and organs. They are responsible for the body's senses and movements.
Spinal cord
The spinal cord is a column of nervous tissue located in the spinal column. It sends messages between the brain and the rest of the body.

Multidisciplinary team (MDT)

Your treatment will usually be organised by a multidisciplinary team (MDT). Your MDT may include some of the following healthcare specialists:

  • a neurologist - a doctor who specialises in treating conditions of the nervous system (the nerves, brain and spinal cord)
  • an orthopaedic surgeon - a surgeon who specialises in treating conditions that affect the muscles, joints and bones
  • a physiotherapist - a healthcare professional who is trained to use physical methods, such as massage and manipulation, to promote healing
  • an occupational therapist - a healthcare professional who can help to identify problem areas in your everyday life, such as dressing yourself, then helps you to work out practical solutions

Charcot-Marie-Tooth disease (CMT) can cause a number of further health complications, and this condition may affect your lifestyle in general.

Breathing difficulties

In rare cases, Charcot-Marie-Tooth disease (CMT) affects the nerves that control your diaphragm (a muscle that is used to help you breath). This can lead to breathing difficulties. For example, you may always feel out of breath.

Always report any breathing-related symptoms to your GP as soon as possible because any problem with your ability to breathe needs prompt treatment.

If you have breathing difficulties, you may be prescribed bronchodilator medicines, which can assist your breathing by widening your airways. See the Health A-Z topic about Bronchodilator medicines for more information. In more severe cases, you may need to use a mechanical breathing aid, such as a ventilator.

If you are overweight, try to lose weight. Reaching your healthy weight will reduce the stress on your diaphragm and make breathing easier.

Depression

Living with a long-term (chronic) condition that you know will get worse can be very stressful. This can lead to depression.

If you have been feeling down during the past month and you take no pleasure from things you used to enjoy, you may have depression.

Talking to other people who are living with CMT may reduce feelings of isolation and stress.

Cognitive behavioural therapy (CBT)

Some studies have shown that a type of therapy called cognitive behavioural therapy (CBT) can help people to cope better with a chronic condition, such as CMT.

CBT is based on the principle that the way you feel partly depends on the way you think about things.

Training yourself to react differently to your condition, using relaxation techniques and keeping a positive attitude has been shown to reduce pain and stress levels. You are also more likely to maintain a healthy lifestyle and diet, which will also help you to cope better with your CMT.

Studies have shown that people with CMT who are employed tend to cope better with their condition than people who do not work. If finding paid work is difficult, you could consider doing voluntary activities.


Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.