Charcot-Marie-Tooth Disorder

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Introduction

Even after being a widespread disorder, Charcot–Marie–Tooth Disorder still does not have an apparent recognition in India. This is basically due to unawareness and lack of proper diagnosis. Ignorance of the facets of CMT deprives a person from living a deserved quality life. Hence it has become inevitable to develop and spread the knowledge of this disorder among the patients & medical practitioners in order to fight and refrain it.

An Overview of Charcot–Marie–Tooth Disorder

Charcot-Marie-Tooth Charcot–Marie–Tooth
Charcot–Marie–Tooth, or CMT, is the most commonly inherited neurological disorder, affecting approximately 1 in 2,500 adults. CMT is found world–wide in all races and ethnic groups. It was discovered in 1886 by three physicians, Jean–Martin–Charcot, Pierre Marie, and Howard Henry Tooth.

Charcot–Marie–Tooth Disorder patients slowly lose normal use of their feet/legs and hands/arms as nerves to the extremities degenerate and the muscles in the extremities become weakened because of the loss of stimulation by the affected nerves. Many patients also have some loss of sensory nerve function.

Charcot–Marie–Tooth Disorder is one of the 40 diseases covered by the MDA, but unlike muscular dystrophy, in which the defect is in the muscles, CMT is a disorder in which the defect is in the nerves that control the muscles.

Charcot–Marie–Tooth Disorder usually isn’t life–threatening and almost never affects brain function. It is not contagious, but it is hereditary and can be passed down from one generation to the next. CMT…


Characteristics and Symptoms of CMT

Although there are many different genetic causes of Charcot–Marie–Tooth Disorder, all types tend to have remarkably similar symptoms. What follows is a general description of these symptoms. Individual patients may not experience all of these symptoms, and the severity of the symptoms may vary greatly from one person to the next.

A high arched foot is usually one of the first signs of this disorder, although in some instances extremely flat feet are also typical of Charcot–Marie–Tooth Disorder. As the disease progresses, structural foot deformities take place. The patient may develop a pes cavus (high–arched) foot and hammer toes.

The progressive muscle wasting of Charcot–Marie–Tooth Disorder also leads to problems with walking, running, and balance. Ankle weakness and sprains are common, and many patients develop foot drop. To avoid tripping, patients with foot drop raise their knees unusually high, resulting in the high “steppage” gait associated with Charcot–Marie–Tooth Disorder. In some patients, muscle weakness may also occur in the upper legs.

Later in the course of the disease, hand function may become affected. Progressive atrophy of the thenar muscle and the small muscles in the hand results in weakening or loss of the opposable pinch, and tasks requiring manual dexterity become difficult. Patients have problems writing, holding utensils, buttoning clothing, grasping zipper pulls and turning doorknobs. Many people benefit from occupational therapy which helps people accomplish the tasks of daily living with the use of assistive devices.

The loss of nerve function is often accompanied by tingling and burning sensations in the hands and feet. This usually causes little more than mild discomfort, but some people experience severe neuropathic pain and require medication to control it.

At the same time, loss of nerve function in the extremities can also result in sensory loss. The sense of touch is diminished, as is the ability to perceive changes in temperature. Sensory loss notwithstanding, many patients are extremely sensitive to the cold or even to temperatures a few degrees lower than normal. The “stocking–glove” pattern of atrophy results in the loss of insulating muscle mass, which, combined with reduced muscular activity and circulation, can leave patients with chronically cold hands and feet. Impairment of the normal circulatory process can also result in swelling (edema) of the feet and ankles.

In many patients, deep–tendon reflexes, such as the knee jerk reaction, are lost. This does not cause any particular problem but is often noted on physical exams. Some people with Charcot–Marie–Tooth Disorder also have tremor (usually of the hands) and the combination of tremor and Charcot–Marie–Tooth Disorder is sometimes referred to as Roussy–Levy Syndrome.

Weakness of the respiratory muscles is in rare in people with Charcot–Marie–Tooth Disorder, but when present, it can cause life–threatening problems. If shortness of breath is an issue, a patient should be checked by a respiratory specialist to see if the use of a ventilator is recommended.

Another problem related to Charcot–Marie–Tooth Disorder can be scoliosis or mild curvature of the spine. This often occurs in puberty and tends to be most common in people with early onset of gait abnormalities. Hip dysplasia also affects a small number of CMT patients at an early age.

As noted, the severity of symptoms can vary greatly from patient to patient, even within the same family. A child may or may not be more severely disabled than his/her parent. Some family members may experience significant impairment and require bracing while others have no noticeable symptoms but are found to have CMT upon examination by EMG or nerve conduction studies.

Diagnosis of Charcot–Marie–Tooth Disorder

Charcot–Marie–Tooth Disorder is usually first noticed when someone develops lower leg weakness and foot deformities such as foot drop, hammer toes and high arches, but that alone will not lead to diagnosis. Sensory loss is often identified when the doctor tests for deep tendon reflexes, such as the knee jerk, which are reduced or absent in CMT patients.

Since Charcot–Marie–Tooth Disorder is strongly hereditary, it is important to tell the doctor about any other family members with CMT–like symptoms. Lack of family history does not rule out CMT, but it will cause the doctor to look further to rule out other causes of neuropathy such as diabetes or exposure to certain chemicals or drugs.

Further testing may be electrodiagnostic, genetic, or both. Electrodiagnostic testing used to diagnose CMT usually includes a nerve conduction velocity test (NCV), which measures the strength and speed of electrical signals moving down the peripheral nerves. Delayed responses are a sign of demyelination (type 1) and small responses are a sign of axonopathy (type 2). An electromyogram (EMG) is also used to measure the electrical signal’s strength in the muscles of the arms or legs.

Genetic tests, done by drawing blood, are available to test for many, but not all, of the common chromosomal defects causing Charcot–Marie–Tooth Disorder. A positive genetic test can provide definitive diagnosis and provide useful information for family planning. However, a negative result does not rule out CMT since some forms cannot yet be tested by DNA sampling. Currently, 18 types can be identified by DNA testing: 1A, 1B, 1C, 1D, 1E, 1F, 1X, 2A, 2E, 2I, 2J, 2K, 4A, 4E, 4F, HNPP, CHN, and DSN.

Types and Causes of Charcot–Marie–Tooth Disorder

The nervous system consists of motor neurons and sensory neurons. One set of nerves carries messages from the brain outward to the rest of the body and one brings messages from the extremities back to the brain. Messages that travel from the brain down the spinal cord, through the lower motor neurons (such as the sciatic nerve of the leg) to the muscles of the body are part of the motor neuron circuitry. Messages that travel upward from the sensory input to the spinal cord and finally the brain are sent by sensory neurons.

The peripheral nervous system is also comprised of motor and sensory nerve fibers, and since Charcot–Marie–Tooth Disorder affects the peripheral nerves, it results in both motor symptoms (weakness and muscle wasting) and sensory symptoms (numbness). The peripheral nerves are often described as being like electrical wires with an inner core (the axon), which is wrapped in insulation (a sheath called myelin). When the myelin is damaged (Type 1 CMT), the nerve impulses are conducted more slowly than normal. If the axon itself is damaged (Type 2), the speed of nerve conduction is almost normal, but the strength of the signal is reduced.

All forms of Charcot–Marie–Tooth Disorder are either demyelinating or axonal in nature. Since Charcot–Marie–Tooth Disorder is a multi–gene disorder, there are many different defective genes, which cause the disorder. Since 1991, more than 30 different genes causing CMT have been identified and the loci are known for at least another ten causes.

Treatment and Management of Charcot–Marie–Tooth Disorder

Treatment of Charcot–Marie–Tooth Disorder is done in conjunction with medical professionals of various specialties. After diagnosis by a neurologist, CMT patients are usually directed to either a podiatrist for care of their foot problems, an orthotist for the manufacture and fitting of braces, an orthopaedic surgeon for surgeries to straighten toes, lengthen heel cords or lower arches, or a physical therapist or occupational therapist to design exercise programs to strengthen muscles or learn energy conservation.

Although there is no cure for Charcot–Marie–Tooth Disorder at the present time, there are many therapies that can greatly improve life and function for CMT patients. The general advice for patients seeking assistance is to look first for the least invasive way to correct their problems.

In general, it is important for people with Charcot–Marie–Tooth Disorder to maintain what movement, muscle strength and flexibility they have. Hence, physical therapy and moderate activity are recommended. Overexertion, however, should be avoided. Swimming or water therapy is an excellent form of exercise since it does not put undue stress on the joints. A physical therapist can design an exercise program that fits a patient’s personal strengths and flexibility. It is impossible to build up muscles already atrophied by CMT, so the best program works on strengthening unaffected muscles that can help do the work of those that have atrophied because of CMT.

Bracing is another non–invasive form of correcting problems caused by CMT. Often gait abnormalities can be corrected by the use of either articulated (hinged) or unarticulated, molded braces called AFOs (ankle–foot orthoses). These braces help control foot drop and ankle instability and often provide a better sense of balance for patients. There are many new forms of bracing available for CMT patients, depending, of course, on the severity of their foot deformities and muscle weaknesses.

Appropriate footwear is important for people with CMT. Because of lack of good sensory reception in the feet, Charcot–Marie–Tooth Disorder patients may also need to see a podiatrist for help in trimming nails or removing calluses that develop on the pads of the feet. It is important to consult a medical professional so that the patient does not injure himself/herself doing these procedures.

The final decision a patient might make in caring for his/her foot or leg deformities is to have surgery. Many patients choose to stabilize their feet or correct progressive problems. These procedures include straightening and pinning the toes, lowering the arch, and sometimes, fusing the ankle joint to provide stability. Recovery from these surgeries can be long and sometimes difficult. Before considering surgery, a patient should always ask what the benefits may reasonably be considered to be and that must be weighed against the problems that might be incurred.

An additional problem related to Charcot–Marie–Tooth that needs to be addressed by a medical professional is the pain that some patients experience. Pain might be sharp and sudden or the gnawing, continuous ache of chronic pain. Some pain is associated with dysfunctional nerves that fire off sporadically and some can be attributed to weakened and poorly functioning muscles. Joints and ligaments in the feet and ankles are often painful because of the extra strain put on them by other muscles that have been rendered useless by CMT. Because the causes of pain vary, so will the treatments. No one, however, should be told that there is no pain associated with CMT, since pain is experienced in a very personal and individual way.

Although medical professionals are involved in many stages and forms of treatment, the patients themselves are responsible for much of the management of their CMT. Basically, people with Charcot–Marie–Tooth Disorder are healthy individuals and they must work to maintain that health. Because circulation is a problem in individuals with Charcot–Marie–Tooth, people must take care to keep their hands and feet as warm as possible. They also should take extra care to avoid falling because fractures take longer to heal in someone with an underlying disease process. Additionally, the resulting inactivity may cause the CMT to worsen. Falls can generally be avoided by watching where one walks and by wearing appropriate footwear.

There is no magic nutritional diet to treat Charcot–Marie–Tooth Disorder, but it is important for CMT patients to control their weight. Not only does extra weight make physical activity more difficult, but it also increases the stress on already compromised joints and muscles.

It is also important for patients to maintain as much strength and flexibility as possible. Generally, patients should consult a physical therapist or physician before beginning an exercise program, and avoid strenuous activity and overwork. Moderate activity and physical exercise can be beneficial, but patients must be conscious of their physical limitations. Patients must learn to say no to tasks that overwhelm them and to delegate tasks to other members of their family when possible.

Finally, stress management is important in maintaining a healthy body. Any disabling condition can affect the way people think and feel about themselves, but having a chronic illness like Charcot–Marie–Tooth Disorder, which is often unseen, places stress on individuals and often causes depression. People with Charcot–Marie–Tooth Disorder can suffer from low self–esteem and relationships with others can be affected. Even when a person has learned to live with Charcot–Marie–Tooth Disorder, the progressive nature of the disorder may bring about more loss and the grieving process can begin again.

Some patients cope successfully on their own or with the support of family and friends; others find it therapeutic to talk to a professional counselor or to participate in a support group

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