Abstract
Brief resolved unexplained events (BRUEs) have numerous and varied causes posing a challenge to investigation and management. A subset of infants with the neuromuscular disorder sodium channel myotonia, due to mutations in the SCN4A gene, experience apnoeic events due to laryngospasm (myotonia) of the upper airway muscles that may present as a BRUE. We sought to ascertain the frequency, severity and outcome of infants carrying the G1306E SCN4A mutation commonly associated with this presentation. We report 14 new cases of individuals with the G1306E mutation from three unrelated families and perform a literature review of all published cases. Infants with the G1306E mutation almost universally experience laryngospasm and apnoeic events. The severity varies significantly, spans both low and high-risk BRUE categories or can be more severe than criteria for a BRUE would allow. At least a third of cases require intensive care unit (ICU) care. Seizure disorder is a common erroneous diagnosis. Apnoeas are effectively reduced or abolished by appropriate treatment with anti-myotonic agents. Probands with the G1306E mutation who are family planning need to be counselled for the likelihood of post-natal complications. There is readily available and extremely effective treatment for the episodic laryngospasm and apnoea caused by this mutation. Proactively seeking clinical evidence of myotonia or muscle hypertrophy with consideration of CK,EMG and genetic testing in high risk BRUEs or more complex apnoeic events may reduce avoidable and prolonged ICU admissions, patient morbidity and potentially mortality.
Highlights
Brief resolved unexplained events (BRUEs) have numerous and varied causes posing a challenge to investigation and management
Any further responses from the reviewers can be found at the end of the article Introduction Brief resolved unexplained events BRUEs are defined by the American Academy of Pediatrics (AAP) as a sudden, brief (
A subset of infants, present with respiratory symptoms and/or laryngospasm due to myotonia of the respiratory and upper airway muscles[5,6]. The severity of these episodes varies from self-resolving in seconds to prolonged or recurrent events known as SNEL: severe neonatal episodic laryngospasm associated with hypertonia, apnoea, loss of consciousness and bradycardia[7]
Summary
Any reports and responses or comments on the article can be found at the end of the article. Keywords Sodium channel, Muscle Disease, Myotonia, Laryngospasm, Stridor, Apnoea, Channelopathy, Paediatric. This version takes account of both reviewer’s comments. A subset of infants, present with respiratory symptoms and/or laryngospasm due to myotonia of the respiratory and upper airway muscles[5,6] The severity of these episodes varies from self-resolving in seconds to prolonged or recurrent events known as SNEL: severe neonatal episodic laryngospasm associated with hypertonia, apnoea, loss of consciousness and bradycardia[7]. Even in adults this mutation is regarded as somewhat of an outlier causing myotonia at the severe end of the spectrum, the description of symptoms caused by the mutation being termed “myotonia permanens”[8]. We report 14 new cases from three unrelated families with the G1306E mutation and review the literature of all described cases to determine the extent, severity and treatment of myotonic symptoms and in particular respiratory complications
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