Myotonic dystrophy is a form of muscular dystrophy that causes progressive weakening of the muscles. Symptoms include muscle stiffness, weakness in the neck muscles, frontal baldness, heart disorders, and metabolic problems. The disease affects various systems in the body and can result in cognitive dysfunction and hypersomnia.
Myotonic dystrophy, also known as myotonic dystrophy (DM) or Steinert’s disease, is a form of muscular dystrophy. Muscular dystrophies, or myotonias, are a group of conditions that cause progressive weakening of the muscles. Symptoms of myotonic dystrophy can vary widely due to the involvement of many systems in the body. One of the most distinguishing symptoms is muscle stiffness; muscle relaxation, which normally occurs after muscle contraction, is significantly delayed in this condition, resulting in general stiffness. This can be demonstrated by a patient trying to relax their hand after gripping an object for an extended period of time. In myotonic dystrophy, the patient would not be able to immediately relax the grip without assistance.
Symptoms of myotonic dystrophy begin in the face, progressing down to the shoulder girdle. Subsequently, foot movements, such as dorsiflexion, are lost. Facial manifestations of myotonic dystrophy symptoms include a characteristic “axe-face” appearance. This physiognomy presents itself as a hollow of the muscles around the temples due to the involvement of the temporal muscles with a “hooding” of the eyes. In later stages, the lower half of the face sags, with a drooping of the lower lip due to atrophy of the masseter and orbicularis muscles of the mouth.
Another distinguishing feature of myotonic dystrophy is that proximal muscles remain relatively stronger than their distal counterparts throughout the disease. However, quadriceps weakness can occur in a number of patients. For example, a patient may have relatively strong leg muscles but profound ankle dorsiflexion weakness, resulting in a striking foot drop.
Early symptoms of myotonic dystrophy may include weakness of the neck muscles, especially the sternocleidomastoids and flexors. Frontal baldness is another early manifestation, along with severe muscle weakness of the distal extremities. Later manifestations include involvement of the tongue and pharynx, resulting in a nasal voice, severe swallowing problems, and dysarthric speech patterns, in which a patient would have difficulty articulating words.
The symptoms of myotonic dystrophy are also present in other systems of the body, especially in the circulatory system. Heart disorders are quite common in myotonic dystrophy, especially in DM1 patients. These heart problems are mainly concentrated in electrical disturbances of the myocardium or heart muscle. First-degree heart blocks are also common. Complete heart blocks are less common than first degree, but can still occur in a good number of patients. Other heart abnormalities, such as congestive heart failure and heart-pulmonary disease, may also occur.
In fact, various systems within the body are affected during the course of myotonic dystrophy. For example, metabolic problems such as insulin resistance and diabetes are common. Gastrointestinal disturbances including constipation and decreased gastrointestinal motility may also occur. Myotonic dystrophy also produces mental disorders, leading to cognitive dysfunction and hypersomnia. Testicular atrophy and cataracts can also occur in this condition.
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