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What is Charcot Marie Tooth Disease (CMT)? What is Peroneal Muscular Atrophy?

charcot marie tooth disease
CMT affects the feet.

Note that Charcot Marie Tooth disease is NOT the same as Charcot Joint or Charcot’s Arthropathy.  These are a complication of diabetes and are covered in Podiatry FAQ 99.

Charcot-Marie-Tooth disease (CMT) is one of the most common inherited neurological disorders, affecting approximately 1 in 2,500 people. Males slightly out number female sufferers. It is also known by its more anatomical description – peroneal muscular atrophy – which describes the nature of the disease.  The term ‘peroneal muscles’ relates to the muscle group that sits to the outside of the shin bone in the lower leg. The word ‘atrophy’ means wasting away. CMT effects the nerves that supply the peroneal muscle group causing it to lose size, strength and the ability to perform its function properly. The nerve damage affects both motor (movement) and sensory (feeling) parts of the nerves. Physically, the nerve enlarges with an excessive amount of myelin sheath coating it which stops its normal function.  In the body, muscles have an ‘equal but opposite’ partner with which they balance.  In the leg, this is the tibial muscle group on the inside of the shin bone. The classic, very high arch of CMT comes about because the tibial muscles are no longer properly opposed by the peroneal group.  They get free reign then to work without an opposing balance and they pull up the arch, tipping the foot outwards.  This creates instability, tiredness and can lead to ankle sprains.

Examination of a person with CMT will show weakness of some leg and foot muscles, clawing of the toes and progressively higher and higher arches as the person ages. Often they will walk with a ‘high stepping’ gait and have impaired balance resulting in trips and falls. The lower legs come to look like an “inverted champagne bottle” due to the loss of low down muscle bulk. Later, weakness and muscle atrophy may progress to the hands, resulting in difficulty with fine movements. CMT symptoms most often start in adolescence or early adulthood but can be delayed until mid-adulthood. They progress gradually with age and the severity of the symptoms varies quite a lot between people, even within the same family. Some suffers will experience very little pain and some a lot. Life expectancy is normal and mental aptitude is not affected.  Children who may have CMT should have their hip function tested as there is an increased chance of a condition called hip dysplasia which has complications later in life.

Diagnosis of CMT begins with a family history and assessment of muscle strength in the arms, legs, hands, and feet. There will be signs of decreased muscle size, poor tendon reflexes, and loss of feeling The feet will usually show high arches, hammertoes and supinated (tipped out) heels.  Electrical conduction tests might be used to assess the sped at which an electrical current can travel from one end of the nerve to the other.  Occasionally, a small piece of the nerve may be extracted for examination under a microscope. Genetic testing can detect some types of CMT and can be used for genetic counseling for parents who carry the genetic condition. Most types of CMT have a 50% chance of being inherited by offspring though some have a lesser chance.

How is Charcot-Marie-Tooth disease treated?

charcot marie tooth disease
An AFO brace used later to cope with foot drop.
charcot marie tooth disease
An ankle brace that might be used early in the condition.

There is no cure for CMT with management focusing on stretching exercises, strengthening and bracing of the foot and leg for the most part.  Orthopaedic surgery may be used to fuse together a joint affected by the disease and pain relieving drugs may be necessary if your CMT is of a painful variety. The physical therapy is best prescribed by a professional, probably a physiotherapist, with relevant experience and is best started as early as the diagnosis is made. Swimming and cycling will often be preferred over walking as a method to maintain fitness.

If CMT has progressed beyond mild to moderate,  ankle braces will be required to maintain mobility and prevent injury. High cut boots and shoe heels that flare to the outside can also help.  As the disorder worsens, the brace may be extended upwards to the thigh and have a non-pivoting ankle area to prevent the foot from drooping down as the heel is lifted off the ground.

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