Characteristics and Symptoms of CMT
Although there are many different genetic causes of CMT, 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 CMT. As the disease progresses, structural foot deformities take place. The patient may develop a pes cavus (high-arched) foot and hammertoes.
The progressive muscle wasting of CMT 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 CMT. 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 muscles at the base of the thumb and other small muscles in the hand results in weakening or loss of the opposable pinch, and tasks requiring manual dexterity become difficult. Patients have problems holding writing 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, and patients may unknowingly injure themselves. They can be unaware of having developed ulcers of the feet or of cuts or burns on the hands. Sensory loss in CMT patients may also be associated with dry skin and hair loss in the affected areas. In rare cases, sensory loss can lead to gradual hearing impairment and, sometimes, deafness.
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 CMT also have tremor (usually of the hands) and the combination of tremor and CMT is sometimes referred to as Roussy-Levy Syndrome.
Weakness of the respiratory muscles is in rare in people with CMT, 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 CMT 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. (Click here for more information about scoliosis.) 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.