Myotonia

Myotonia is delayed muscle relaxation after voluntary contraction or electrical stimulation, often causing stiffness. It results from prolonged muscle-fiber electrical activity.

Muscle membrane: The specialized cell membrane that conducts electrical signals along a muscle fiber. Myotonic discharges persist in the membrane after a contraction.
Myotonia congenita: An inherited disorder caused by CLCN1 variants, characterized mainly by muscle stiffness and delayed relaxation. It is the classic chloride-channel form of myotonia.
Electromyography: A test that records the electrical activity of skeletal muscles. It detects the characteristic repetitive discharges of myotonia.
Muscle weakness: Reduced ability to generate normal force with a muscle or group of muscles. Myotonia delays relaxation; weakness concerns reduced force production.
Voltage-gated chloride channel: A membrane protein that carries chloride ions in response to changes in electrical voltage. Reduced chloride conductance is a major cause of inherited myotonia.
Thomsen disease: The autosomal dominant form of myotonia congenita, usually beginning in childhood. Its inheritance pattern distinguishes one major CLCN1-related presentation.
Grip myotonia: Delayed opening of the hand after forceful gripping. This visible sign can help identify myotonia during examination.
Muscle spasticity: Increased resistance to passive movement caused by abnormal central nervous system reflexes. Spasticity arises from central nervous system injury, unlike muscle-fiber myotonia.
CLCN1: A gene encoding the skeletal-muscle chloride channel ClC-1. Variants in CLCN1 commonly produce myotonia by impairing muscle-fiber electrical stability.
Becker disease: The autosomal recessive form of myotonia congenita, often more severe than Thomsen disease. It illustrates a more severe inherited chloride-channel presentation.

Linked from 2 pages