Comparison of in vitro contracture testing with ryanodine, halothane and caffeine in malignant hyperthermia and other neuromuscular disorders.

In vitro exposure of living skeletal muscle to ryanodine has been proposed as a potentially specific test for malignant hyperthermia (MH). In this study we have compared in vitro contracture responses to halothane, caffeine and ryanodine in skeletal muscle specimens obtained from 155 patients attending for diagnosis of susceptibility of MH and also from six patients having muscle biopsy for diagnosis of other neuromuscular disorders. Although the ryanodine contracture test was not specific for MH, the results suggest it may greatly aid (in conjunction with the standard halothane and caffeine contracture tests) the accurate phenotyping of individuals that is essential for the further genetic analysis of MH.