Charcot-Marie Tooth Disease

Charcot-Marie Tooth Disease (CMT) is an inherited condition of the peripheral nervous system that results in muscle wasting and progressive change in the mechanical properties of the leg and foot. The impact of CMT on the foot is directly due to peroneal muscle atrophy.

CMT is characterized by two types;

Type I

The characteristic finding of Type I CMT begin to develop in the late teens to early 20's. The most pronounced finding is the 'stork leg deformity' that occurs as the peroneal muscles of the lower leg begin to atrophy (become weak). Muscular wasting of the hands does occur but typically happens well after the onset of atrophy of the legs. Type I CMT progresses slowly over the patient's lifetime.

Neurological findings of Type I CMT include;

A decrease in the ability of the peripheral nerves of the hand and feet (a stocking glove distribution) to sense vibration, pain and temperature

Deep tendon reflexes are absent

EMG testing shows slow nerve conduction velocities with prolonged distal latencies.

Enlarged peripheral nerves that can be felt

Type II

Type II CMT shows many of the same neurological finding, only that they appear much later in life.

Treatment: Currently, there is no available method to slow or stop the progression of CMT therefore treatment is based upon symptoms. Many CMT patients require no treatment at all. Others find comfort in soft prescription orthotics or AFO braces that stabilize the leg.

No information is available for this topic.

Charcot-Marie Tooth Disease is also referred to as peroneal atrophy.  So let's take a look at the peroneal muscles, their origin (where they originate and attach proximally), their insertion (where they attach distally) and their function (what they do).

Peroneus brevis -

Origin - Just below the knee on the lateral (outside) aspect of the leg on the posterior margin of the fibula (outside bone of the leg). Continues down the leg rounding the ankle just behind the fibula (outside bone of the ankle).
Insertion - Base of the 5th metatarsal bone on the lateral (outside) aspect of the midfoot.
Function - Acts to stabilize the foot during the mid-stance phase of the gait cycle (as the body passes over the foot). Also acts to assist the Achilles tendon to plantarflex the foot.

Peroneus longus -

As peroneal muscle wasting progresses in CMT, several biomechanical events begin to take place. Consider the fact that every muscle in our bodies requires an antagonist; a muscle that works against it to balance and decelerate its' function.

Example; to hit a tennis ball with a backhand shot you need a strong triceps (back of the arm) muscle. But that action needs to be slowed by another muscle on the other side of the arm (the biceps muscle). Without this slowing effect, the elbow wear out very quickly. This fine balance is also a physiological characteristic that allows for fine tuning of motion.

Now let's consider the imbalance that occurs with CMT. The muscle that is the antagonist of the peroneus longus is the tibialis anterior, located on the top of the foot. This tendon can easily be seen on the top of the foot as you pull your foot and toes towards you and roll in your foot. With the progressive loss of the peroneal muscles, especially the peroneus longus, the tibialis anterior muscle and tendon begin to acquire more power. Loss of one, gain of the other results in structural change of the foot which is seen as an increase in the height of the arch.

As a result of peroneal muscle atrophy, the leg becomes increasingly more and more thin.  A characteristic high arch will develop as a result of loss of the peroneal muscles.  Inversion of the heels occurs and callus appears beneath the 1st and 5th metatarsal heads.

CMT patients will often exhibit the same symptoms of other patients who have very high arches. In many cases, the fat pad beneath the metatarsal heads, just behind the toes on the bottom of the foot, will atrophy. This results in painful calluses. Other CMT patients will have difficulty being able to wear lace up shoes due to the height of the arch and the pressure that is focused on the top of the foot by a lace up shoe. Additional symptoms include lateral ankle instability as a result of a plantarflexed 1st metatarsal and inverted heel.

The differential diagnosis for CMT includes:

Clubfoot
Traumatic injury to the peripheral nerves that supply the peroneal muscles
Peroneal Palsy
Stroke
Paralysis
Muscular dystrophy

• Peripheral Neuropathy

• Peroneal Tendon Subluxation

• Peroneal Tendon Rupture

• Peroneal Palsy

• CT Band Syndrome

This article was written by Jeffrey A. Oster, DPM and last updated 2/5/13. No additional information is available for this topic.