Paramyotonia congenita is a disorder that affects skeletal muscles used for movement.It causes problems with the tone and contraction of skeletal muscles.People with this condition experience bouts of sustained muscle tensing which prevent muscles from relaxing normally. Myotonia causes muscle stiffness that typically appears after exercise and can be induced by muscle cooling. This stiffness chiefly affects muscles in the face, neck, arms, and hands, although it can also affect muscles used for breathing and muscles in the lower body.
HOW IS PARAMYOTONIA CONGENITA DIAGNOSED?
It is diagnosed by an electromyographic (EMG) examination. During this test fine needles are inserted into the muscle and the muscle’s electrical signals are recorded. The muscle is chilled for this test, as chilling brings on the myotonia. Evidence of myotonia supports the diagnosis of PMC.
HOW IS PARAMYOTONIA CONGENITA TREATED?
Some patients do not require treatment to manage the symptoms of paramyotonia congenita. Others, however, require treatment for their muscle stiffness and often find mexiletine to be helpful. Others have found acetazolamide to be helpful as well. Avoidance of myotonia triggering events is also an effective method of myotonia prevention.
DID YOU KNOW?
Sodium channels normally open to cause muscle excitation, and then close to end the excitation. In paramyotonia congenita, mutations in the muscle sodium channel gene prolong the channel’s opening, causing higher-than-normal muscle excitation. It is inherited in an autosomal dominant pattern, meaning it is produced by a defective gene contributed by one parent.