What is Charcot-Marie-Tooth Disease?

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Charcot-Marie-Tooth

Charcot-Marie-Tooth disease is an inherited disorder of the peripheral nerves.  The peripheral nerves are situated on the superficial area of the central nervous system — the brain and the spinal cord, which is connected to the rest of the body. The impairment of the disorder is mostly on the peripheral nerves of the upper and lower extremities — the arms and legs. This is why Charcot-Marie-Tooth disease is also medically termed as “peroneal muscular atrophy (PMA) or hereditary motor and sensory neuropathy (HMSN).”

According to the National Institute of Neurological Disorders and Stroke, Charcot-Marie-Tooth disease is one of the most common inherited neurological disorders impacting 1 out of every 2,500 people in the United States today.

With Charcot-Marie-Tooth disease, muscles tend to become weaker and smaller. As a consequence, the person affected by this disease may experience difficulty in walking, muscle contractions, impaired sensation, foot deformities, and high arches are commonly observed.

Charcot-Marie-Tooth disease was named after Dr. Jean-Martin Charcot, Dr. Pierre Marie, and Dr. Henry Tooth. The physicians who discovered the disorder in 1886.

Signs and Symptoms 

The symptoms of Charcot-Marie-Tooth disease usually happen in adolescent years but may also develop in the mid-adulthood year. Typically, symptoms will start from the lower extremities (legs and feet) and will become apparent to the upper extremities (hands and arms).

Common signs and symptoms of Charcot-Marie-Tooth disease include:

  • Weakness in your feet, ankles, and legs
  • Impaired sensation in the legs and feet
  • Difficulty in standing 
  • Difficulty lifting your foot at the ankle 
  • Frequent tripping or falling
  • High stepping when walking
  • Decreased ability to run
  • Inverted lower legs
  • Loss of muscle bulk in your legs and feet
  • Foot deformities like hammertoes (curled toes) or high foot arches

As Charcot-Marie-Tooth disease progresses, the person may experience difficulty in moving the tongue, hands, wrists, feet, and fingers. The symptoms may spread from the lower extremities to the upper extremities. The complexity of the symptoms differ from person to person and even among the members of the family.

Causes 

As it is said, Charcot-Marie-Tooth disease is a congenital genetic disorder. It is caused by one or more defective genes, due to mutations, that affect the nerves of the upper and lower extremities. The mutation of the genes may cause damage to the nerves or to the protective covering that envelops the nerves called — myelin sheaths. The damage tends to disrupt the function and structure of the peripheral nerve sheath and axons resulting in a weakened signal traveling from the nerves between your extremities and to the brain.

There are some very rare cases wherein people are affected by Charcot-Marie-Tooth disorder without inheriting a defective gene from the parents.

Diagnosis

In the diagnosis of Charcot-Marie-Tooth disease, the physician will initially take note of the detailed family history, medical history, and neurological examination.  

Physical Examination 

This is conducted to check for prominent signs and symptoms of the disorder like: 

  • Signs of muscle weakness in the feet, legs, hands, and arms
  • Sensory loss both in hands and feet
  • Reduced muscle bulk in the lower legs resulting in inverted lower legs
  • Impaired tendon reflexes
  • Apparent foot deformities like curled toes or high foot arches
  • Other orthopedic disorders like deformed hip joint and mild scoliosis.

A prominent sign of an individual affected by this disease is the enlarged nerve that may be felt or seen through the skin most especially on the elbow area. The abnormally thickened myelin sheaths cause the enlargement of the nerves — hypertrophic nerves.

To view the severity of the nerve-damaged and determine the causative factors, the physician may recommend the following extensive medical procedures:

Nerve Conduction Studies

This test will measure the strength and function of electrical signals of the nerves. During the test, small electrodes were placed on the skin. Then a small number of electric shocks will be transmitted to stimulate the nerve. A weak or delayed response may be an indication of nerve disorder like Charcot-Marie-Tooth disease.

Electromyography (EMG)

This electromyography (EMG) test is performed by inserting a thin needle electrode through the skin into the muscle. The needle electrode is attached to a wire that is connected to the machine. The patient will be required to gently flex and relax the muscle while the machine measures the electrical activity of the muscle. With the electromyography (EMG) test, the physician will be able to check the extent of the disease by means of testing different muscles.

Nerve Biopsy

The surgeon is the one who conducts this nerve biopsy.  This procedure involves the removal of a small piece of the peripheral nerve from the calf through a small incision in the skin of the leg. The nerve specimen will be subjected to laboratory analysis to distinguish the appearance of Charcot-Marie-Tooth disease from other forms of nerve disorders.

Genetic Testing

This genetic testing uses the blood sample of the patient. This test can detect the defects in the genes caused by Charcot-Marie-Tooth disease. This genetic testing may provide more information for the benefit of family planning. Medical experts suggest that it is important to seek genetic counseling prior to undergoing the test to be aware of the pros and cons of the testing.

Risk Factors

Since Charcot-Marie-Tooth disease is a congenital genetic disorder, there is a higher risk of developing the disease if any of the immediate members of the family is affected by it. 

Other causes of neuropathies that may cause symptoms identical to or worst than the Charcot-Marie-Tooth disease may include:

  • General disease like diabetes
  • Injury to the nerves caused by physical trauma
  • Chronic diseases like kidney disorders and hypothyroidism
  • Deficiency in Vitamins B1, B6, B12 and E
  • Severe alcoholism
  • Toxic chemical exposure like solvents, insecticides, or glue
  • Exposure to heavy metals like mercury and lead
  • Infection — certain bacteria and viruses directly attack the nerve tissue. For viruses like varicella-zoster and herpes simplex. For bacterial infections like Lyme disease. Those infected with HIV or AIDS may also develop peripheral neuropathy.
  • Autoimmune disease like lupus and rheumatoid arthritis also affects the peripheral nervous system
  • Chronic inflammation may also lead to severe nerve pain in the extremities
  • Certain medications may also cause damage to the nerves like anticonvulsants used for seizures, chemotherapy medications, blood pressure medications, antibacterial drugs, some hypercholesterolemia medications, and certain cardiovascular disease medications.

Treatment

Unfortunately, there was no known cure for Charcot-Marie-Tooth disease. Typically, the progress of the disease takes slowly and the lifespan of the person is not at stake.

Some medical management can be done to alleviate the difficulties of the people with Charcot-Marie-Tooth disease, and this may include:

  • Pain reliever medications
  • Physical exercises
  • Physical therapy
  • Occupational therapy
  • Surgery for severe foot deformities
  • Use of orthopedic devices

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