Muscular dystrophy versus mitochondrial myopathy: the dilemma of the undiagnosed hypotonic child

As pediatric anesthesiologists, it is unusual in these days of complex technology and advances in genetic research to find ourselves presented with conflicting information and continued controversy regarding anesthesia plans for a particular group of children. This still occurs, however, when presented with the task of determining the best management for the child with an undiagnosed myopathy (1‐6). Drs Flick et al. (1) in this issue of Pediatric Anesthesia have taken their 13 years of experience to help guide the thought processes for this population of children. The authors reviewed the charts of all children who had undergone muscle biopsies to rule out suspected neuromuscular disorders (NMD). All of the children received volatile anesthetic agents with or without succinylcholine and no child in the review of 274 charts developed malignant hyperthermia (MH) or rhabdomyolysis from the delivered anesthetic. Seven of the patients had biopsies consistent with muscular dystrophy and three consistent with mitochondrial disorder. Although the results of this review should be comforting, no child in their population was subsequently diagnosed with Evans myopathy, King syndrome or central core disease, the only known disorders that are truly associated with malignant hyperthermia (7). Any of these diagnoses would have certainly changed the results, but not the conclusion. Appropriately, Flick et al., rather than assigning a risk of zero based on their findings, have estimated the risk of a patient with NMD to have MH or rhabdomyolysis from exposure to a volatile anesthetic at less than or equal to 1.09%. This is in comparison with the 0.46% risk in an MH-susceptible child of developing an episode of malignant hyperthermia after nontriggering anesthesia (6).