CMT is primarily a disease of the nerves, whereby the myelin or insulating sheath of myelin on the nerves does not stay intact (demyelination) and the messages from the brain to the muscles through the nerves are not carried properly. It differs from muscular dystrophy, in that people who have muscular dystrophy have a problem with their muscles from the beginning, while those with CMT are born with normal muscles. The muscles atrophy, or waste away, because the CMT afflicted nerves that serve them cannot properly send the messages from the brain for them to move. Therefore, muscles can atrophy even though they are being used.
CMT is not well known, but it is not rare. In fact, it is often overlooked by doctors when diagnosing foot deformity, although it accounts for 45% of the disorders that cause them. It has been estimated that the prevailence of CMT is one in 2500, making it the most common inherited peripheral neuropathy. Many people do not know that they have CMT, even though it is carried in families sometimes for generations. CMT can be inherited three ways, but most cases are inherited autosomal dominate pattern, meaning it comes down a line from parent to child. In this form of inheritance there is a 50/50 chance at each conception that the child will have CMT.
CMT is characterized by slow progression of symptoms with initial involvement of the feet and legs, followed several years later by involvement of the hands. Outward signs are what doctors look to begin a diagnosis of CMT. Children with the disease often walk on their toes, and adults consult a doctor because of abnormalities of gait, foot deformities, such as hammertoes, or loss of balance. Tripping over objects on the floor and ankle sprains are frequent due to weakness in the dorsiflexion of the foot produced by weakness of the peroneal and anterior tibial muscles. Balance is usually affected because the muscles of the feet are weak and cannot compensate for a sudden stop or a change in terrain. Even standing still can be very difficult and someone with CMT will often have to reach out and just touch something to be able to stand still. Pes cavus deformity is usually not seen early in the disease, but seems to progress with age. Atrophy of the distal legs may be a prominent feature in some patients, but a thicker layer of subcutaneuos fat may mask the leg muscle atrophy. Cramps are a frequent complaint of CMT people and they are worse after long walks.
Primary symptoms in the upper extremities are finger, hand and grip, as well as wrist weakness, the loss of the muscle that makes the thumb move, and a loss of feeling and/or movement in the hand and wrist. Weakness of the hand muscles usually occurs late in the course of the disease, but may not be related to the degree of leg weakness or atrophy. The most frequent complaint concerning hand involvement is difficulty buttoning and unbuttoning, using zippers, and manipulating small objects when using fine finger movements. In severe cases, the wasting of the intrinsic hand muscles may give the appearance of claw hands. Scoliosis and other spinal deformities are often diagnosed in people who show CMT at an early age, and some people experience hip and knee dislocations, while some are born with deformed hip sockets.
Other symptoms of CMT can include very cold or very hot feet, painful hands, and symptoms not unlike carpal tunnel syndrome, where there is numbness and pain in the wrist and little fingers; in fact, a person can have carpal tunnel and CMT or CMT that is diagnosed as carpal tunnel if the doctor doesn't look at the rest of the patient. Pain from nerve deterioration and weak, tired, overworked muscles is common and a lot of CMT people are in constant pain. Fatigue is one of the prime symptoms that everyone with CMT seems to experience. Pacing and moderation are recommended. A feeling of nerve or muscle crawling (a feeling of small insects crawling all over the skin), called formication, and burning, mainly on the soles of the feet and palms of the hands and sometimes the behind and back of thighs, as well as tremors, can also be part of CMT. Sciatic leg pain and foot pain are also common.
Diagnosis can also be made by doing and electromyogram (EMG) that measures the irritability and function of muscles and motor nerve conduction velocity (MNCV) tests that establish the ability of nerves to send and receive impulses. Electrophysiological studies distinguish two major forms of CMT: CMT type 1 (CMT1) is a demyelinating neuropathy with moderate to severely decreased motor nerve conduction velocity, wherein clinical features appear to be do to fiber loss and denervation, while type 2 (CMT2), the neuronal form, shows normal to only mildly reduced nerve contraction velocity. Although clinical manifestations of CMT1 may not be present until early adolescence or adult-hood, the electrophysiological abnormalities are evident by an early age and usually by the age of two.
CMT can cause severe disability in some cases, but as stated before, most people have it so mildly they do not know they have it. Symptoms of CMT vary greatly in each individual. How it manifests itself all depends on a person's genetic makeup, their lifestyle, activities, diet, and everything else that makes up their life. Extreme or prolonged stressors have been known to make a person with CMT worse. There are also many medications which may aggravate or exacerbate CMT; therefore, people with CMT should ask their doctor or pharmacist to look for the words "could cause peripheral neuropathy" in the drug description before taking any medication. Alcohol and tobacco are also thought to exacerbate CMT, as are mega doses of vitamins A, B6 and D.
There are more alternative therapies and drugs to control pain being learned about all the time. Surgery can help foot, ankle, hand, finger, spine and hip problems. Ankle-foot orthotics (AFOs) can also help a person with foot-drop walk without tripping and in-shoe orthotics can help alleviate pain experienced when walking and give a person an improved gait. There is also much genetic research that is ongoing, and the genes that cause some of the many types of CMT have already been found.
With an early diagnosis and by taking care of themselves, people with CMT will live a normal life span, without too much difficulty. It is said that the best form of dealing with CMT is to live well. People who have CMT should treat themselves, not overdo anything, and learn to pace themselves.