Abstract Details

Title ICU Management of Severe Myotonic Crisis in the Setting of Beta-Adrenergic Agonist Use: A Case Report

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P10 - Poster Session 10 (5:00 PM-6:00 PM)

Poster/Presentation
Number 11-012

Objective NA

Background Nondystrophic myotonias (NDM) include skeletal muscle sodium and chloride channelopathies, which result in muscle hyperexcitability due to a postsynaptic channel mutation. Rarely, myotonic disorders are complicated by “myotonic crisis,” a severe, generalized, sustained muscle contraction classically caused by succinylcholine. These crises are distinct from malignant hyperthermia (MH) because they lack features of hypermetabolism including hyperthermia and acidosis. We describe critical care management of a pediatric patient with SCN4A-associated NDM who developed a severe MH-like crisis in the setting of recent illness and beta-adrenergic agonist use.

Design/Methods NA

Results A 10-year-old female with SCN4A-associated NDM and asthma presented to the ED with status asthmaticus and was treated with continuous albuterol and intravenous steroids. She developed worsening myotonia, rhabdomyolysis, and acidosis. Despite mexiletine and lorazepam, she developed progressive respiratory failure necessitating intubation. Due to severe masseter spasm, she was intubated via a trans-laryngeal mask airway fiberoptic approach. Her ICU course included worsening respiratory failure, persistent severe muscle rigidity with associated rhabdomyolysis, and hyperthermia. Multi-modal pharmacologic therapy targeted both presynaptic and postsynaptic signaling in the myocyte contractile apparatus, allowing for muscle relaxation. She was extubated after 13 days and discharged after 28 days with rehabilitation to near-baseline function. Genetic testing did not reveal additional risk factors for MH susceptibility. Six and ten months post-discharge, she had two short admissions for asthma exacerbations managed without beta-adrenergic agonists, and was discharged both times without myotonic crisis.

Conclusions

Existing literature suggests myotonic crises are physiologically distinct from MH. However, severe generalized muscle contraction, in this case precipitated by an SCN4A gain-of-function mutation and exacerbated by beta-adrenergic agonist use, can lead to features of hypermetabolism including hyperthermia and acidosis. This case promotes careful consideration when prescribing beta-adrenergic agonists to patients with known or suspected myotonia, and provides guidance for early critical care management of patients presenting with severe crises.

Authors/Disclosures
Ashna Aggarwal PRESENTER	Miss Aggarwal has nothing to disclose.
Anil Wadhwani, MD, PhD (Hospital of the University of Pennsylvania)	Dr. Wadhwani has stock in Eli Lilly. The institution of Dr. Wadhwani has received research support from NIH.
Steven Loscalzo, MD	Dr. Loscalzo has nothing to disclose.
Megan McSherry, MD	The institution of Dr. McSherry has received research support from NIH Postdoctoral Research Training in Perioperative Medicine (5T32GM112596-09).
Justin Lockman, MD	Dr. Lockman has nothing to disclose.
John Brandsema, MD (Children's Hospital of Philadelphia, Division of Neurology)	Dr. Brandsema has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Biogen. Dr. Brandsema has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Genentech. Dr. Brandsema has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for PTC Therapeutics. Dr. Brandsema has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Sarepta. Dr. Brandsema has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Novartis. Dr. Brandsema has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Argenx. Dr. Brandsema has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Janssen. Dr. Brandsema has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Dyne. Dr. Brandsema has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Takeda. Dr. Brandsema has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Scholar Rock. Dr. Brandsema has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Edgewise. Dr. Brandsema has received personal compensation in the range of $500-$4,999 for serving as an officer or member of the Board of Directors for CureSMA. The institution of Dr. Brandsema has received research support from Novartis. The institution of Dr. Brandsema has received research support from Biogen. The institution of Dr. Brandsema has received research support from Alexion. The institution of Dr. Brandsema has received research support from CSL Behring. The institution of Dr. Brandsema has received research support from Pfizer. The institution of Dr. Brandsema has received research support from PTC Therapeutics. The institution of Dr. Brandsema has received research support from Sarepta. The institution of Dr. Brandsema has received research support from Astellas. The institution of Dr. Brandsema has received research support from Fibrogen. The institution of Dr. Brandsema has received research support from Genentech. The institution of Dr. Brandsema has received research support from Janssen. The institution of Dr. Brandsema has received research support from Scholar Rock.
Jennifer McGuire, MD (Children's Hospital of Philadelphia)	Dr. McGuire has received research support from NIH.
Susan Matesanz, MD	Dr. Matesanz has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Sarepta. Dr. Matesanz has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Novartis. Dr. Matesanz has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Atamyo . The institution of Dr. Matesanz has received research support from Sarepta . The institution of Dr. Matesanz has received research support from Pfizer. The institution of Dr. Matesanz has received research support from Genentech/Roche.

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