What is CMT?
CMT is a condition that affects the nerves in your legs and arms, known as the peripheral nerves.
Our body’s system of nerves is like a network of electrical wires. Some of them, called sensory nerves, are designed to pass information back to the brain about what you can feel with your fingers, toes, legs and arms, etc. The others are command pathways, telling your muscles to do something, like lift your left foot – and are called motor nerves.
Because CMT affects both types of peripheral nerve, you may experience motor problems as the command pathways fail to respond properly, causing weakness and wasting in your muscles and numbness/sensory problems, arising from the problems with the sensory nerves.
The condition is not life threatening and affects people very differently, even within the same family. It slowly gets worse over time (is progressive), causing gradual deterioration of both the motor nerves and the sensory nerves this deterioration causes atrophy of the muscles in the foot, lower leg, hand and forearm and can cause foot drop walking gait, foot bone abnormalities (including high arches and hammer toes), problems with hand function and dexterity, balance problems, occasional cramping in the legs and arms and loss of some normal reflexes. It may cause long term pain and chronic tiredness. It is usually passed on from parent to child, with a 50% chance of the child inheriting the condition. It is thought to affect approximately 23,000 people in the UK. It affects all ethnic groups equally throughout the world.
The first noticeable signs are often slight difficulty in walking because of problems picking up the feet. The muscles that support the foot in a normal walking gait are among the first to be affected, and therefore the toes drop as the foot is lifted, causing a tendency to trip, and an awkward walking gait.
Children may have problems with apparent clumsiness, or lack of agility, even before any other noticeable symptoms.
Many people with CMT have very highly arched feet (known medically as pes cavus) and this may be noticeable from a very early age. This can often lead to instability of the foot and ankle, with twisting of the ankles becoming very common. However, it is also possible to have a very flat foot, which can also be a problem.
Curled or hammer toes are a very common symptom and can cause problems with shoes causing pain.
The legs can have a characteristic shape – known as the inverted champagne bottle – with the lower legs, below the knees, being very thin, and the thigh muscles retaining a normal shape and muscle bulk.
Symptoms can progress noticeably at the time of the growth spurt associated with puberty.
Some sensory loss and numbness is usual in both the arms and legs, but is rarely troublesome. Rarely, this numbness can be severe, and it is easy then for individuals to injure themselves without knowing it.
Exceptionally cold hands and feet are also common, caused by poor circulation in the extremities.
The hands and forearms tend to become affected as the disease progresses, and can lead to loss of fine motor control, dexterity and overall hand strength, making doing up buttons difficult and undoing jam-jars and bottles almost impossible.
Pain is often a feature of CMT, and is usually a result of poor walking – an unbalanced foot and ankle leads to additional stress on the knees, hips, back and even shoulders and neck. More rarely, the damaged nerves themselves cause pain, known as neuropathic pain, which is much more of a problem to bring under control.
It is also possible to have some tremor in both the arms and legs. Severe tremor and CMT can be known as the Roussy-Levy Syndrome.
Later in life, there can be increased difficulty in walking, and aids may be needed, such as orthoses (splints), walking sticks, and wheelchairs, although it is rare for someone with CMT to become a permanent wheelchair user. Many people use wheelchairs for occasional use, to relieve the pain and effort of walking.