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Paramyotonia and MH 580 CANADIAN JOURNAL OF ANAESTHESIA reports about all cases available so far for analysis. Pend- ence of anaesthetic triggers. In myotonic dystrophy, there ing further evidence, the association of fentanyl with is an abnormal influx of extracellular calcium, leading MAOIs should not be condemned on the basis of a sole, to muscle damage. In a report by Aldridge of 49 an- inconclusive case. aesthetics given to 17 myotonic dystrophy patients, there were no cases of MH, despite the frequent use of volatile Ph. Baele MD agents. 7 This is the largest series reported in such patients, Y. Kestens-Servaye as far as I am aware. Newberg et al. were unable to M. Goenen MD trigger MH episodes in myotonic goats, the classic animal Department of Anesthesiology model of myotonia congenita. 8 Department of Intensive Care Hopefully, as we gain more knowledge about the UCL St-Luc 1200 Brussels pathophysiology of muscle disorders, a number of mis- conceptions regarding the association of MH to other REFERENCES myopathies can be put to rest. 1 Noble WH, Baker A. MAO inhibitors and coronary artery surgery: a patient death. Can J Anaesth 1992; 39: 1061-6. Gregory C. Allen MD FRCPC 2 Fobe F, Kestens-Servaye Y, Baele PH, Goenen M. Heart- Assistant Professor of Anesthesia transplant and mono-amine oxidase inhibitors. Acta Department of Anesthesia Anaesthesiol Belg 1989; 40: 131-8. College of Medicine Penn State University Hershey, Pa 17033 U.S.A. REFERENCES Paramyoton& and MH 1 Howell PR, Douglas MJ. Obstetric Forum - Lupus anti- coagulant, paramyotonia congenita and pregnancy. Can J To the Editor: Anaesth 1992; 39: 992-6. It is incorrect for Drs. Howell and Douglas to include 2 Ashwood EM, Russell W J,, Burrow DD. Hyperkalaemic paramyotonia congenita in "a group of disorders which periodic paralysis and anesthesia. Anaesthesia 1992; 47: are called the myotonic dystrophies. "l While both pa- 579-84. ramyotonia congenita and myotonic dystrophy cause ep- 3 MacKenzie AE, Korneluk RG, Zorzato F, et al. The isodes of myotonia and muscle weakness, only myotonic human ryanodine receptor gene: its mapping to 19q 13.1, dystrophy is characterized by progressive muscle wasting placement in a chromosome 19 linkage group, and exclu- and atrophy. Signs and symptoms of paramyotonia con- sion as the gene causing myotonic dystrophy. Am J Hum genita are limited to skeletal muscle, but myotonic dys- Genet 1990; 46: 1082-9. trophy affects all three types of muscle, as well as other 4 Brownell AKW. Malignant hyperthermia: relationship to organ systems. Finally, paramyotonia congenita and hy- other diseases. Br J Anaesth 1988; 60: 303-8. perkalaemic periodic paralysis appear to be the same dis- 5 Lehmann-Horn F, Iaizzo PA. Are myotonias and periodic order, with a gene locus on chromosome 17 (sodium chan- paralyses associated with susceptibilityto malignant hyper- nel a-subunit). 2 The gene locus for myotonie dystrophy thermia? Br J Anaesth 1990; 65: 692-7. is located on chromosome 19. 3 6 Koch MC, Steinmeyer K, Lorenz C, et al. The skeletal Dr. Crone states that malignant hyperthermia (MH) muscle chlorid channel in dominant and recessive human is associated with the myotonias, without citing refer- myotonia. Science 1992; 257: 797-800. enees. The only myopathy definitely associated with MH 7 Aldridge LM. Anaesthetic problems in myotonic dys- is central core disease. 4 No cause-effect relationship has trophy. Br J Anaesth 1985; 57:1119-30. been made between MH and the myotortias. Contracture 8 Newberg LA, Lambert EH, Gronert GA. Failure to in- test results in myotonic patients have been negative or duce malignant hyperthermia in myotonic goats. Br J equivocal, s Malignant hyperthermia is a disorder of skele- Anaesth 1983; 55: 57-60. tal muscle calcium homeostasis; myotonia congenita is a chloride channel disorder (chromosome 7), 6 and pa- REPLY ramyotonia is due to a sodium channel defect; 2 MH and We wish to thank Dr. Allen for updating our information with myotonic dystrophy are both characterized by raised in- respect to the genetics of the myotonias and hyperkalemic pe- riodic paralysis. At the time that the article was written much tramyoplasmic calcium concentrations, but by two dif- of the information that he quotes was unavailable. In fact, the ferent mechanisms, s In MH, a defect in the sarcoplasmic 1992 ASA Refresher Course on MH still listed myotonia con- reticulum causes uncontrolled calcium release in the pres- genita as a disease that appears possibly related to MH. .
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