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October 1992

Myotonia Fluctuans

Arch Neurol. 1992;49(10):1010-1011. doi:10.1001/archneur.1992.00530340026009

To the Editor.  —Ricker et al1 recently described a family with an autosomally inherited myotonic disorder that they called myotonia fluctuans. There were no dystrophic features; it differed from myotonia congenita and paramyotonia congenita in fluctuating in severity, being unaffected by cold, and showing delayed worsening after excercise. There were no episodes of weakness, and the myotonia was exacerbated by potassium loading. We report similar features in another family, confirming that myotonia fluctuans is a clinically recognizable entity and emphasizing its relatively benign nature.

Report of a Case.  —A 22-year-old woman gave a history of myotonia from the age of 9 years, at times causing painful spasms. The myotonia affected all her muscles, including the rectus abdominis muscle after sneezing. She had periods during which her symptoms worsened substantially for no definite reason; she felt that these fluctuations were loosely associated with spells of damp weather. There was no