Myotonic Syndrome

Myotonic syndromes are characterized by persistent muscle contraction and slowed decontraction (relaxation).

Action myotonia - slow decontraction occurs during free contraction of the muscle.

Mechanical myotonia - slowed decontraction occurs as a response to mechanical irritation.

The greatest myotonic manifestations are at the beginning of the movement. With repeated movement and exercise, they shrink and disappear.

Therapy

 * There is no curative therapy only symptomatic pharmacological therapy such as phenytoin or hydatoins (of the neuromuscular symptoms, the own myotonia can only be minimally affected by administering phenytoin in a daily dose of 200 mg), carbamazepine, mexiletine

Clinical Types

 * Myotonia congenita – AR or AD hereditary disease. Patients have only myotonic manifestations and tend to be of a muscular habit. Myotonia fluctuans − AD hereditary disorder with manifestations of fluctuating myotonia of varying intensity Mytonia permanens − severe and permanent disorder; caused by a sodium channel defect
 * Myotonic dystrophy – an autosomal dominantly inherited systemic disease, in which myotonic syndrome is combined with manifestations of myopathy, which, however, does not have a typical girdle localization, but more distal involvement prevails. There is also typically weakness of the cervical flexors and sternocleidomastoids, atrophy of the masseters and also mm. temporalis. Polyneuropathy and impairment of other systems are also present - intellectual deficit, cataract, atrophy of the gonads, impairment of the cardiac conduction system and impaired glucose tolerance. Patients are at risk of sudden cardiac death. The disease is incurable.