Charcot-Marie-Tooth disease (CMT) is an inherited condition of the nerves. The nerves that carry signals between the brain and the muscles slowly stop working. Muscles that no longer get a signal become weak and waste away. The nerves that carry feeling are often affected too, so numbness is common.
The longest nerves are hit first, so the first signs are usually in the feet and lower legs. Over the years the weakness can move up the legs and into the hands. Symptoms often begin in the teens or early adult life. How bad it gets varies a lot, even within one family, but it tends to worsen slowly over time.
CMT affects about one person in 2,500. It is the most common inherited condition of the nerves and muscles. It is usually looked after by a neurologist, with help from a physiotherapist, podiatrist, orthotist and sometimes an orthopaedic surgeon.
Different types of Charcot-Marie-Tooth – Classification and Significance
Many different genes can cause CMT. The types are grouped by which part of the nerve is damaged:
- CMT1, where the fatty coating around the nerve (the myelin) is damaged. Signals travel slowly. The most common type of all, CMT1A, is in this group
- CMT2, where the nerve fibre itself (the axon) breaks down. Signals travel at normal speed but fewer get through
- Rarer types that affect only the nerves to the muscles, and mixed types that do not fit neatly in either group
Knowing the type helps with genetic advice for the family. Treatment of the feet is much the same for all types.
Differential Diagnosis
A few other rare conditions can look like CMT, including nerve damage from other causes, motor neurone disease and some muscle diseases. Nerve tests and genetic testing tell them apart.
Symptoms
Symptoms come on slowly and are usually first noticed in the feet:
- High arches and clawed or hammer toes, as the small muscles of the foot waste
- Weak ankles, with the foot slapping down or catching on the ground (foot drop)
- Tripping, frequent ankle sprains and an awkward walk
- Trouble running and finding shoes that fit
- Numbness in the feet, which many people do not notice until they are checked
- Burning nerve pain, or aching pain from joints that have changed shape
- Later, weakness and wasting in the hands
Loss of feeling is the symptom to watch. A blister, a burn or a stone in the shoe can go unnoticed and turn into an ulcer. Daily checks of the feet are part of living with CMT.
Causes
CMT is caused by a fault in one of the genes that build or maintain the nerves to the arms and legs. The faulty gene is passed down through families.
Some faults damage the nerve fibre itself. Others damage the fatty coating that lets signals travel fast. Either way, fewer messages get through between the brain and the feet and hands.
Muscles that stop getting messages become weak and waste. Feeling is lost as well, so pain messages from the feet may not reach the brain.
Risk Factors
- Family history. This is the main risk factor. Some types are passed from an affected parent to half their children. Some need a faulty gene from both parents. Some are carried on the X chromosome and mostly affect boys
- Some chemotherapy drugs, which can speed up nerve damage in people who already have CMT
Investigations
A neurologist can often make the diagnosis from the story and the examination. Tests confirm it and show the type:
- Nerve conduction studies, which measure how fast and how strongly signals travel along the nerves
- Genetic (DNA) testing on a blood sample, which finds the faulty gene in most people
- Sometimes a nerve biopsy, though this is rarely needed now
Foot and ankle X-rays are used when surgery is being considered, to measure the shape of the foot.
Complications
- Ulcers and infections of the feet from lost feeling and pressure from deformed toes
- Ankle sprains and falls
- Arthritis of the foot and ankle joints that have been pulled out of shape
- Curving of the spine (scoliosis) in some people
- Hand weakness that makes fine tasks difficult
- Loss of the ability to walk. This is uncommon in the most frequent type (CMT1A) but can happen in the more severe types
Treatment
There is no cure for CMT yet, but a lot can be done to keep people walking well and free of foot problems. Care is shared between a neurologist, a physiotherapist, a podiatrist, an orthotist and, when needed, an orthopaedic surgeon.
Exercise and physiotherapy
Regular moderate exercise keeps the muscles that still work as strong as possible and helps balance. Swimming, cycling and walking are good choices. Heavy weight training and pushing a weak muscle to exhaustion are avoided, as they can make weakness worse. A physiotherapist who knows neuromuscular conditions can set the right level.
Shoes, insoles and braces
Good footwear is the most useful everyday treatment:
- Insoles (orthotics) that support the high arch and spread pressure so calluses and ulcers do not form
- Deep, wide shoes with room for clawed toes
- An ankle brace or a light splint (an ankle foot orthosis) for foot drop and weak ankles, which stops tripping and sprains
See Footwear in Orthopaedics for more on how shoes and insoles help.
Foot care
Because feeling is reduced, check the feet every day for red marks, blisters and cuts. See a podiatrist regularly for nail and callus care. Treat any wound early.
Pain relief
Aching from joints that have changed shape usually responds to paracetamol and sometimes anti inflammatory medicines. Burning nerve pain needs different medicines, and a pain specialist may be involved.
Surgery
Surgery is considered when the foot shape causes pain, instability or pressure sores that shoes and insoles cannot manage. Operations fall into two groups:
- Soft tissue surgery, which moves tendons from a strong muscle to a weak one, or releases tight tissue, to rebalance the pull on the foot
- Bone surgery, which cuts and realigns bones (osteotomy) or fuses stiff painful joints (arthrodesis) to give a flat, stable foot
CMT keeps progressing, so a deformity that is corrected can return as more muscles weaken. Fused joints also raise the chance of arthritis in the joints next to them. Surgeons therefore operate when the benefit is clear, and the expected result is discussed carefully beforehand.
Future Treatments for CMT
Trials of high dose vitamin C for CMT1A did not show a benefit. Research now centres on drugs that protect the nerve coating and on gene therapy, both still in trials. Ask your neurologist about current studies, as the picture changes.
Seeking Advice
Your Family Doctor (GP)
Your Family Doctor will be able to diagnose and help treat your problem. He or she will be able to
- tell you about your problem
- advise you of the best treatment methods
- prescribe you medications
- and if necessary, refer you to Specialists (Consultants) for further treatment
While you might first discuss your symptoms with your family doctor, he or she will probably refer you to a neurologist for further evaluation.
Prevention
As Charcot-Marie-Tooth is an inherited disease, there is currently no way to prevent it.
F.A.Q. | Frequently Asked Questions
Will my children inherit it?
It depends on the type. The most common form is passed on in a dominant pattern, which means each child of an affected parent has a one in two chance of inheriting the gene. Other types follow different patterns, including some that need a gene from both parents and some passed on through the X chromosome. Because the answer varies, genetic counselling is the best way to get a figure for your own family.
Will I end up in a wheelchair?
Most people with CMT keep walking throughout life, often with the help of braces or orthotics. A minority, usually with the more severe types, need a wheelchair for longer distances. It is not the usual outcome, and it is not a sudden event.
Does it shorten life?
For the common forms, no. CMT affects the nerves supplying the limbs; it does not usually affect life expectancy.
Is exercise safe?
Yes, and moderate exercise is encouraged, as it maintains strength, balance and general health. What is discouraged is exercising a weakened muscle to exhaustion, which can be counterproductive. A physiotherapist experienced in neuromuscular conditions can set the level.
Are there medications I should avoid?
Some drugs can worsen nerve damage, so it is important that any doctor prescribing for you knows you have CMT, including before chemotherapy or a general anaesthetic. Ask your neurologist for the current list, as lists found online may be out of date.
What can be done about the foot shape?
A high arch and clawed toes are common and cause pressure problems and instability. Custom orthotics, supportive footwear and ankle braces help most people. Where the deformity is fixed or the foot is unstable, surgery to rebalance tendons, correct bone alignment or fuse joints can improve walking and reduce the risk of skin breakdown. See claw toes and footwear in orthopaedics.