Severe Masseter Muscle Rigidity Following Succinylcholine Administration in a Patient with Inconclusive Pharmacogenetic Results for Susceptibility to Malignant Hyperthermia: A Case Report

Jedniphat Intrapongpan; Naruemon Vattanasiriporn; Thitinuch Ruenhunsa; Saranyoo Nonphiaraj; Sarinya Chanthawong; Chanapat Charoensuk

Authors

Jedniphat Intrapongpan Department of Anesthesiology, Faculty of Medicine, Khon Kaen University
Naruemon Vattanasiriporn Department of Anesthesiology, Faculty of Medicine, Khon Kaen University
Thitinuch Ruenhunsa Department of Anesthesiology, Faculty of Medicine, Khon Kaen University
Saranyoo Nonphiaraj Department of Anesthesiology, Faculty of Medicine, Khon Kaen University
Sarinya Chanthawong Department of Anesthesiology, Faculty of Medicine, Khon Kaen University
Chanapat Charoensuk Department of Anesthesiology, Faculty of Medicine, Khon Kaen University

Keywords:

masseter muscle rigidity, succinylcholine, malignant hyperthermia, RYR1 protein, CACNA1S protein, anesthesia

Abstract

Masseter muscle rigidity following succinylcholine is traditionally viewed as a potential early indicator of malignant hyperthermia (MH), although most adult cases remain isolated without systemic progression. We report a 50-year-old woman who developed immediate, severe bilateral masseter rigidity after succinylcholine during induction of general anesthesia. Despite profound limitation in mouth opening of approximately 1.5 cm, videolaryngoscopic intubation was achieved on the first attempt, and mask ventilation remained uncomplicated. The rigidity persisted even after administration of cisatracurium, yet the patient demonstrated no systemic signs of MH, with normal hemodynamics, end-tidal CO₂, temperature, and laboratory values. Surgery was cancelled, and the rigidity gradually resolved during recovery in the intensive care unit. Targeted genetic testing for RYR1 and CACNA1S variants did not identify pathogenic mutations. However, given the limited scope of the tested variants, the result was considered inconclusive for determining MH susceptibility. This case illustrates that marked succinylcholine-induced masseter rigidity can occur without progression to systemic MH. It also highlights that nondiagnostic targeted genetic testing reflects current limitations in variant detection and should not be interpreted as definitively excluding susceptibility. In patients presenting with significant isolated masseter rigidity, continued MH preparedness remains warranted despite the absence of systemic manifestations during the initial event.

References

Litman RS, Rosenberg H. Malignant hyperthermia: Update on susceptibility testing. JAMA 2005;293(23):2918-24. doi:10.1001/jama.293.23.2918.

Wappler F. Malignant hyperthermia. Eur J Anaesthesiol 2001;18(10):632-52. doi:10.1046/j.1365-2346.2001.00888.x.

Larach MG, Gronert GA, Allen GC, et al. Clinical presentation, treatment, and complications of malignant hyperthermia in North America from 1987 to 2006. Anesth Analg 2010;110(2):498-507. doi:10.1213/ANE.0b013e3181c6b9b2.

Rosenberg H, Pollock N, Schiemann A, et al. Malignant hyperthermia: A review. Orphanet J Rare Dis 2015;10:93. doi:10.1186/s13023-015-0310-1.

Hopkins PM. Malignant hyperthermia: Pharmacology of triggering. Br J Anaesth 2011;107(1):48-56. doi:10.1093/bja/aer132.

Riazi S, Kraeva N, Hopkins PM. Malignant hyperthermia in the post-genomics era: New perspectives on an old concept. Anesthesiology 2018;128(1):168-80. doi:10.1097/ALN.0000000000001878.

Hopkins PM, Rüffert H, Snoeck MM, et al. European malignant hyperthermia group guidelines for investigation of malignant hyperthermia susceptibility. Br J Anaesth 2015;115(4):531-9. doi:10.1093/bja/aev225.

Kim DC. Malignant hyperthermia. Korean J Anesthesiol 2012;63(5):391-401. doi:10.4097/kjae.2012.63.5.391.

Carpenter D, Robinson RL, Quinnell RJ, et al. Genetic variation in RYR1 and malignant hyperthermia phenotypes. Br J Anaesth 2009;103(4):538-48. doi:10.1093/bja/aep204.

Klingler W, Rueffert H, Lehmann-Horn F, et al. Core myopathies and risk of malignant hyperthermia. Anesth Analg 2009;109(4):1167-73. doi:10.1213/ANE.0b013e3181b5ae2d.

Glahn KP, Ellis FR, Halsall PJ, et al. Recognizing and managing a malignant hyperthermia crisis: Guidelines from the European Malignant Hyperthermia Group. Br J Anaesth 2010;105(4):417-20. doi:10.1093/bja/aeq243.

Gonsalves SG, Dirksen RT, Sangkuhl K, et al. Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for the use of potent volatile anesthetic agents and succinylcholine in the context of RYR1 or CACNA1S genotypes. Clin Pharmacol Ther 2019;105(6):1338-44. doi:10.1002/cpt.1319.

Hopkins PM, Girard T, Dalay S, et al. Malignant hyperthermia 2020: Guideline from the association of anaesthetists. Anaesthesia 2021;76(5):655-64. doi:10.1111/anae.15317.

Gupta PK, Bilmen JG, Hopkins PM. Anaesthetic management of a known or suspected malignant hyperthermia susceptible patient. BJA Educ 2021;21(6):218-24. doi:10.1016/j.bjae.2021.01.003.

Rüffert H, Bastian B, Bendixen D, et al. Consensus guidelines on perioperative management of malignant hyperthermia suspected or susceptible patients from the European Malignant Hyperthermia Group. Br J Anaesth 2021;126(1):120-30. doi:10.1016/j.bja.2020.09.029.