IN 1886 Eulenberg1 described "paramyotonia congenita," an inherited syndrome in which episodes of myotonia and weakness were induced by exposure to cold. A similar condition was reported independently by Rich.2 During the ensuing years additional cases were published, emphasizing the myotonia rather than the episodic weakness which was also part of Eulenberg's original description. A link with periodic paralysis was not considered until 1957, when French and Kilpatrick3 studied a patient with paramyotonia who was subject to attacks of generalized weakness. An oral dose of potassium chloride induced an attack of weakness lasting several days, without a fall in the serum potassium level.
Just prior to the report of French and Kilpatrick, Helweg-Larsen et al4 in Denmark and Gamstorp5 in Sweden described a hyperkalemic form of periodic paralysis, "adynamia episodica hereditaria." Myotonia was not mentioned in these Scandinavian cases, but paralysis could be induced by
Layzer RB, Lovelace RE, Rowland LP. Hyperkalemic Periodic Paralysis. Arch Neurol. 1967;16(5):455–472. doi:10.1001/archneur.1967.00470230007002
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