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What is myotonia?

Myotonia is a neuromuscular disorder characterized by slow relaxation of the muscles after voluntary contraction or electrical stimulation and is caused by an abnormality in the muscle membrane. Individuals with the disorder may have a stiff, awkward gait and trouble releasing their grip on objects or rising from a sitting position. The disorder can affect all muscle groups and may be acquired or inherited.

Myotonia is a symptom commonly seen in patients with myotonic muscular dystrophy and in a group of disorders called channelopathies (hereditary diseases that are caused by mutations in the chloride sodium or potassium channels that affect the muscle membrane). Myotonia also may be triggered by exposure to cold.

Generally, repeated effort is needed to relax the muscles, and the condition improves after the muscles have warmed up.

This Answer is based on source information from the National Institute of Neurological Disorders and Stroke .

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