Charcot Marie Tooth Disease or CMT: Symptoms, Causes, Types, Treatment
This is a neurological disease which is pretty widespread in United States of America. It affects approximately 1 in every 2000 people. Charcot Marie Tooth Disease or CMT is also knows as hereditary sensory and motor neuropathy. It contains a set of impairments that impairs the peripheral nerves. Conditions that affect these nerves are also known as peripheral neuropathy.
Signs and Symptoms of Charcot Marie Tooth Disease or CMT
Neuropathy which arises out of Charcot Marie Tooth Disease or CMT impairs both the motor as well as sensory nerves. One particular feature is that the muscles of the lower leg become weak leading to frequent falls and an impaired gait. There can also be deformities like high arched foot due to the weakness. One additional deformity which can arise due to loss of muscle bulk in the lower extremities is called "champagne bottle deformity." As the disease progresses, the weakness progresses to the upper extremities as well resulting in impairment of fine motor functions in the upper extremities.
The symptoms of Charcot Marie Tooth Disease or CMT generally begin with adolescence, but there have been cases where an individual has developed symptoms in adulthood. The symptoms are variable in their severity from individual to individual. Generally, the symptoms progress gradually and slowly. The pain severity can be mild to fairly severe to the point that some individuals need assistive devices in order to remain mobile. This disease is not life threatening.
Causes of Charcot Marie Tooth Disease or CMT
To understand the causes of Charcot Marie Tooth Disease or CMT, one must know how information is transmitted to brain by the nerves. This communication between the nerves and the brain takes place by a part of cell called as the axon, and for better and faster communication it is protected by myelin that is formed by a cell called as Schwann cell. In Charcot Marie Tooth Disease or CMT, the axon and the myelin sheath is disturbed and hence the nerves are not able to send the signals from the limb to brain.
The main reason behind CMT is the mutation of genes resulting in malfunction of the peripheral nerves and over time the nerves start losing their capacity to interact or communicate with the limb and back to the brain, which results in weakness of the muscle and loss of muscle bulk as well as sensory impairment. The gene mutation that was talked about above is generally inherited.
Types of Charcot Marie Tooth Disease or CMT
There are 5 types of Charcot Marie Tooth Disease or CMT namely CMT-1, CMT-2, CMT-3, CMT-4, and CMT-X, which are described below:
CMT-1: This is basically caused due to myelin sheath abnormality. It has five subtypes CMT1A, CMT1B, CMT1C, CMT1D, and CMT1E.
- CMT1-A: It is an autosomal dominant disorder which is caused due to duplicating genes in chromosome 17. This chromosome is responsible for carrying instructions to produce PMP22 protein, which is a very important part of myelin sheath. This duplication causes abnormality in the function of the myelin sheath. People with CMT1A start having weakness in the lower extremities in their adolescence which progresses to upper extremity weakness and subsequently sensory loss.
- CMT1-B: This is also an autosomal dominant disorder which is due to gene mutation of genes that carry instruction for producing protein P0, another important part of the myelin sheath.
- CMT1-C, CMT1-D, and CMT1-E are rare disorders and have symptoms which are similar to CMT1-A.
- CMT-2: This is different from CMT1 in that this disease is due to abnormality in the axons that are present in the cells of the peripheral nerves and not the myelin sheath. This disease is rare.
- CMT-3: It is a demyelinating neuropathy of a severe nature that starts with infancy with infants having severe muscle weakness and sensory impairments.
- CMT-4: This type of CMT contains several subsets of autosomal recessive motor and sensory neuropathy of a demyelinating nature with each subset being caused by a different gene mutation.
- CMT-X: This disorder is caused by the mutation of the gene called connexin-32 on chromosome-X.
Diagnosis for Charcot Marie Tooth Disease or CMT
- To diagnose Charcot Marie Tooth Disease or CMT, the physician conducts an initial examination comprising of a detailed medical history, family history, and a comprehensive neurological evaluation. When conducting the neurological examination, the physician observes for signs of weakness in the muscles of the extremities, loss of muscle bulk, decrease in the deep tendon reflexes, or any form of impairment in sensation of the individual. Physicians also observe for deformities in the foot like flatfeet etc. A typical sign of CMT in individuals is the enlargement of the nerves which can be clearly observed from the skin.
- If there is a suspected diagnosis of CMT, EMG/nerve conduction studies are ordered. This study is helpful in determining the involvement of the peripheral nerves and to which severity they are involved.
- A physician can also order genetic testing to confirm the diagnosis of CMT.
- If all of the above testing does not give a definite diagnosis of CMT, then a nerve biopsy is performed to confirm diagnosis.
Treatment of Charcot Marie Tooth Disease or CMT
No clear-cut treatment is available for Charcot Marie Tooth Disease or CMT, but the use of physical therapy, occupational therapy, AFOs, and other assistive devices can be used to diminish the symptoms, which are often disabling. Pain medications are also used for severe pain. Exercises such as muscle strengthening, stretching, endurance training, etc. are useful in increasing endurance of an individual so that he or she is able to perform ADLs with relative ease and less fatigue. Braces and other devices are used to provide stability to the joints, which become weak due to the disease.