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What is Charcot-Marie-Tooth disease?
Charcot-Marie-Tooth disease is a group of clinical conditions that affects the body's peripheral nervous system. Charcot-Marie-Tooth disease is a disorder of the peripheral nerves, which are the nerves that lie in the periphery of the body that arise from the brain and the spinal cord. It is a genetic disorder where there is a defect in the formation of the protective insulator sheath around the nerves called myelin sheath. Due to the lack of an intact myelin sheath, conduction of electrical signals along the nerves is interrupted, resulting in muscle weakness and numbness of the skin.
There are different forms of Charcot-Marie-Tooth disease. While in one type there is damage to the myelin sheath, in another type there is damage to the actual nerve fiber itself. The end result is the same, and patients experience muscle weakness and numbness of the skin.
What causes Charcot-Marie-Tooth disease?
Charcot-Marie-Tooth disease is an inherited disorder, meaning it is passed along through generations. In some cases, the chances of developing the disease is around 50 percent (autosomal dominant), while in other cases it can be around 25 percent that exhibit the symptoms and another 25 percent who carried the gene that causes the disease (autosomal recessive). In other words, if both parents do not carry the gene, there is no chance that the child will suffer from Charcot-Marie-Tooth disease.
In certain rare cases, the gene that is responsible for Charcot-Marie-Tooth disease is bound to the X chromosome. Inheritance is a lot more complicated in such a situation.
Symptoms and Diagnosis
The symptoms can vary between patients. Early on in the disease, patients may find that they have become increasingly clumsy and may find it difficult to walk short distances. Symptoms become a lot more prominent as the patient gets older, especially after they pass puberty. The common symptoms that they may experience include weakness of the muscles of the leg and feet, loss of the arch of the foot leading to a flatfoot, difficulty walking and taking very high steps when trying to walk, which is called a high stepping gait. Patients will also lose sensation in their feet and in their arms. When asked to lift their knee up to their chest, their foot points towards the floor rather than staying upright. This is called foot drop.
As the condition gets progressively worse, patients find it harder and harder to perform simple tasks. The alterations in the muscle strength in the lower limbs can cause additional stress elsewhere in the body, leading to joint pains and muscle pains.
On examination, the leg is classically described as having an inverted champagne bottle appearance. The arch of the foot can either be flat or can be exaggerated, causing a high arch or "pes cavus." Patients lose the sensation to position and vibration but are still able to feel hot, cold and pain. Sometimes, the nerve fibers that are involved can also be felt under the skin.
Clinical history and examination are key to making a diagnosis. Certain specialized tests such as genetic testing are required to ascertain the cause and type of Charcot-Marie-Tooth disease. Sometimes, biopsy of the nerve fibers may be performed.
How is Charcot-Marie-Tooth disease treated?
Unfortunately, there is no cure. Simple lifestyle modifications such as cutting down on alcohol intake and caffeine intake and maintaining an ideal body weight should be observed. Treatments are aimed at improving posture and maintaining mobility. Pain relief can help manage joint pains and muscle aches. Painkillers that are offered include antidepressant medication such as tricyclic antidepressants or even anticonvulsant medications, such as carbamazepine.
Surgical treatments are offered in cases where the tendons and muscles are either too tight or too weak. These can include procedures such as joint fusion, or arthrodesis, bone repositioning, or osteotomy, and plantar fascia release.
Physical therapy plays a major role in the treatment of Charcot-Marie-Tooth disease. The aim of physical therapy treatment is maintaining patient independence by performing a variety of exercises that tone and strengthen muscles. In some cases, custom-made orthopedic support devices, like braces or splints, may be offered. In cases where one of the parents suffers from Charcot-Marie-Tooth disease, it may be wise to see a geneticist before embarking on the journey of having a child.