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Pontocerebellar hypoplasia, malignant hyperthermia, and inappropriate use of secondary references

SIR—We were recently consulted to give an opinion about a 2-year-old female child diagnosed with TSEN34related pontocerebellar hypoplasia (PCH) Type 2 who required general anesthesia for radiologic studies. As per the parents, the child’s neurologist warned that children with PCH are predisposed to the development of malignant hyperthermia (MH) during general anesthesia. We consulted the Malignant Hyperthermia Association of the U.S. (MHAUS) and performed a detailed literature search to confirm this association. PCH is an autosomal recessive neurodegenerative disorder characterized by microcephaly, dyskinesia, seizures, and severe cognitive and language impairment. PCH was considered confined to the central nervous system until 2008 when Barth et al. demonstrated a myopathic component in two patients who developed hyperthermia and rhabdomyolysis (1). The only mention of MH in that paper was the statement: ‘Anesthetic accidents resulting in malignant hyperthermia have not been documented in PCH-2, and also are not known to the authors by experience’. But, this same group then published reviews of PCH in which it was stated that MH was, indeed, an anesthetic risk in these patients (2). No references were cited for these claims. This incorrect association was then furthered by additional authors citing these secondary sources (3). A ‘secondary source’ is an account of a scholarly subject that has been previously published elsewhere in its original form, the primary source. At best, a secondary source can be a comprehensive and accurate summary of a compilation of studies or findings concerning a single subject. In the process of preparing a scholarly article, many authors will rely on secondary sources to avoid the workload of reading and digesting all the possible primary sources, as well as to cut down on references to include in their paper. However, a major limitation of the use of a secondary source is that it presents the primary references from someone else’s viewpoint. This viewpoint is oftentimes helpful, but at times may be incorrect because of inaccurate citation or misinterpretation of the findings of the primary reference. When an author relies on incorrect information from a secondary reference, patients can be harmed. When a patient is deemed to be MH susceptible, it leads to significant alterations in anesthetic and perioperative care. For example, the anesthesia machine has to be specially prepared to purge the system of all anesthetic gases, and the anesthesiologist must only use intravenous anesthetics (e.g., propofol, opioids, midazolam, etc.) and nondepolarizing neuromuscular blockers (e.g., vecuronium, rocuronium, etc.). The disadvantages of using this ‘nontriggering’ technique include not only additional time and expense but also the inability to use succinylcholine, one of the most important anesthetic medications because of its role in the immediate relief of life-threatening upper airway obstruction. For these reasons, the designation of ‘MH susceptible’ is not to be taken lightly. The propagation of misinformation due to inaccurate citations is common in the medical literature (4). In our own specialty of anesthesiology, the citation error rate is estimated to be as high as 56% (5). Many of these errors will be composed of inconsequential mistakes in title, volume, etc., but misinterpretations of findings carry the potential to subsequently alter clinical care. Following detailed discussions with the patient’s parents about the lack of relationship between PCH and MH, the patient successfully received routine general anesthesia for her diagnostic studies without complication. The patient’s neurologist was informed of our findings, and the authors of the secondary references were contacted and asked to alter their recommendations, and we are grateful for their cooperation and support. We call on authors and journal editors to discourage the use of secondary sources whenever possible, as inaccurate citation or interpretation may lead to detriments in clinical care.