Isaacs' Syndrome With Muscle Hypertrophy Reversed by Phenytoin Therapy

James Zisfein, Mark Sivak, Alan M. Aron, Adam N. Bender

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


A 16-year-old boy was seen for severe episodic muscle cramps and generalized myokymia, consistent with Isaacs's syndrome. Bilateral calf hypertrophy (46-cm calf circumference) and ankle areflexia were noted. He was treated with phenytoin sodium, 300 mg/ day. Within three months there was marked decrease in myokymia, total relief of cramps, return of ankle reflexes, and 6-cm reduction in calf circumference. We suggest that the excess muscle activity in Isaacs's syndrome may be responsible for the associated phenomena of muscle hypertrophy and areflexia.

Original languageEnglish
Pages (from-to)241-242
Number of pages2
JournalArchives of Neurology
Issue number4
StatePublished - Apr 1983


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