Charcot-Marie-Tooth disease

This is not one disease but a whole family of inherited conditions in which the peripheral nerves gradually fail — the nerves that carry instructions from the spinal cord out to the muscles and bring sensation back. Another name for it is hereditary motor and sensory neuropathy. It affects roughly one person in two and a half thousand, which makes it the commonest inherited disease of the nerves. The signal reaches the feet and hands weakened, so the muscles furthest from the centre waste and sensation becomes blunted. Everything moves slowly, over years and decades; intelligence and memory are untouched and most people have a normal life expectancy. The main thing to take from this text: there is still no cure, yet much of what spoils life with the condition can be prevented, from badly chosen shoes to one drug that must never be given to a person with this diagnosis.

How it starts

The first signs usually appear between the ages of five and fifteen, though sometimes much later, well into adult life; in some people everything stays so mild that the diagnosis turns up by chance. In a child what stands out is not weakness as such but small things that get blamed on personality:

• unusual clumsiness for the age, frequent trips on level ground, ankles that turn over, tiring quickly where other children do not;
• walking with the knee lifted high and the foot slapping down — the body's way around weakness of the muscles that raise the toes;
• a very high arch or, conversely, a completely flat foot, with the toes curled into claws;
• shoes that wear out fast and unevenly, always along the same edge.

In adults the trigger for suspicion is usually an ankle that gives way more and more often, or being unable to stand on the heels. Another clue is the family: a parent or grandparent who "always had odd feet" or whose leg "withered". Such stories are worth half the investigation.

What changes over time

The disease works from the ends of the limbs inwards; the legs are affected first and always more than the arms.

• the calf muscles waste and the leg takes on a recognisable shape: a full thigh above a thin calf;
• the foot stops lifting and the walk becomes high-stepping, with an exaggerated raise of the knee;
• the feet become deformed, calluses build up and the soles ache; later the hands weaken, and buttons, keys in locks, jar lids and handwriting all become difficult;
• sensation fades, the skin distinguishes heat and pain less well, and hands and feet are cold and often bluish;
• cramps appear in the calves, along with aching in muscles and joints from overload and, less often, burning nerve pain;
• fatigue becomes a constant background: every step costs more effort than it does for other people.

Some things get discussed less. In a proportion of people the spine curves, which is why it is watched through adolescence while growth is fast. Trembling of the hands is common and says nothing about severity. And the most serious: in certain uncommon forms the muscles that support breathing and the voice grow weak. A hoarse voice, choking on food, breathlessness when lying flat, morning headaches and waking unrefreshed should all prompt a prompt appointment, because night-time breathing can be supported.

Why it runs in families

The cause is a fault in one of dozens of genes responsible either for the sheath that wraps the nerve or for the fibre that conducts the impulse. In some forms the sheath breaks down and the signal travels slowly; in others the fibre itself is damaged and the signal arrives on time but weak. Hence the differences between people who share the same diagnosis: within one family a father may have nothing but a very high arch while his son has obvious weakness.

Inheritance works in more than one way, and the risk to children depends on which. In the commonest pattern a faulty gene from one parent is enough, and the chance of passing it to each child is one in two. In another, two copies are needed, one from each parent; the parents themselves are well and have no idea they carry it. There is also a form linked to the X chromosome: a mother passes it to her sons, in whom it runs a heavier course, while daughters often have only mild signs. The exact figures for a particular family come from a genetics specialist, and it is wiser to go before a pregnancy rather than after.

Medicines and anaesthetics to warn about

Some drugs are toxic to peripheral nerves. A healthy person tolerates them with moderate consequences, but in someone with this diagnosis they can take away in weeks what the disease itself would have taken decades to remove. Vincristine, an anticancer drug, is absolutely contraindicated: severe paralysis has been described after it in people whose condition had not been recognised. Used with caution and only on strict grounds are other chemotherapy agents from the platinum and taxane groups, some antibiotics given in long courses, certain heart rhythm and antituberculosis drugs, and vitamin B6 in high doses.

From this comes a simple rule: before cancer treatment, before a long course of antibiotics and before any planned operation, the doctor must know your diagnosis. Say so yourself. The anaesthetist is warned separately: in neuromuscular disease the muscle relaxants are chosen differently and breathing is watched more closely after surgery.

How the diagnosis is made

It all begins with a neurological examination: strength in the feet and hands, reflexes, sensation, the shape of the feet and the pattern of walking. Weak or absent reflexes together with a high arch are already a strong argument.

Next comes a nerve conduction study with electromyography, which measures how fast and how strongly a nerve carries an impulse. That test answers the key question: whether the sheath or the fibre is the part in trouble. The diagnosis is confirmed by a blood test for the genetic change, which also pins down the type and with it the outlook and the risk to future children. In some people no known fault is found; that does not overturn a diagnosis made on examination and electromyography, it simply means the gene involved has not been described yet.

What genuinely helps

There is as yet no medicine that halts the disease, and promises to cure it with stem cells in exchange for large sums remain promises. What has accumulated instead is a set of measures that really do change quality of life.

• Regular exercise therapy and stretching, especially of the Achilles tendon: it does not restore strength, but it delays the stiffness that eventually fixes the foot in an awkward position.
• Moderate aerobic activity — swimming, cycling, walking at a comfortable pace, built up gradually and never pushed into pain.
• An ankle brace for a dropping foot: a well-fitted one removes half the trips and falls.
• Shoes with a firm heel counter and a roomy toe box, made to measure if necessary.
• A daily look at the feet. With reduced sensation a rubbed patch or a burn from a hot water bottle goes unnoticed and turns into a slow-healing wound; test bath water with your hand, not your foot.
• Everyday aids: thickened handles, fastenings instead of buttons, jar openers. Small things that give independence back.
• Keeping weight in check: extra kilograms land on muscles that are already weakened.
• Pain relief matched to the type of pain: ordinary anti-inflammatory drugs suit muscle and joint pain, while nerve pain needs the medicines designed for it.

Surgery is not for everyone and not from the outset. It corrects a foot deformity once walking is affected and footwear no longer solves it, and it corrects a curved spine. An operation does not repair the nerve; it makes the foundation more comfortable, and recovery takes months. The emotional side deserves separate mention: a slowly progressive condition wears a person down as much as physical weakness does, and talking therapy or a support group is no luxury here.

Online consultation

A remote appointment is a good place for the questions that usually hang in the air. What the identified type means and what to expect from it. What the risk to children is and when to see a geneticist. How to structure activity so that it helps rather than exhausts. Which of the medicines prescribed to you by others call for caution. The doctor will ask what began and when, how walking and hand strength have changed, who in the family had similar signs, and will say whether a face-to-face neurological examination, nerve conduction studies or a genetic test are needed. What is not for a screen: breathlessness, choking and hoarseness appearing for the first time. Those need assessment in person, and a growing struggle for breath needs emergency care.

This material is for information only and does not replace medical advice.