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any disorder involving tonic spasm of muscle. adj., adj myoton´ic.
myotonia atro´phica myotonic dystrophy.
myotonia conge´nita a hereditary disease marked by tonic spasm and rigidity of certain muscles when attempts are made to move them. The stiffness tends to disappear as the muscles are used.
myotonia dystro´phica myotonic dystrophy.