Acute myotonic reaction during succinylcholine anaesthesia.

A 21-year-old woman developed an acute myotonic reaction while undergoing anaesthesia using succinylcholine. Examination later showed she had shoulder, neck and calf hypertrophy, bilateral symmetrical ptosis and eyelid, handgrip and percussion myotonia. Peripheral neurophysiology studies identified significant, continuous myotonic discharges in both upper and lower limbs. Genetic analysis identified a c.3917G>A (p.Gly1306Glu) mutation in the SCN4A gene, confirming a diagnosis of sodium channel myotonia. Succinylcholine and other depolarising agents can precipitate life-threatening acute myotonic reactions when given to patients with myotonia. Patients with neuromuscular disorders are at an increased risk of perioperative anaesthetic complications. We report a woman who developed an acute myotonic reaction whilst undergoing anaesthesia, in the context of an unrecognised myotonic disorder. We then discuss an approach to the diagnosis of myotonic disorders.

Skeletal Muscle Channelopathies: Rare Disorders with Common Pediatric Symptoms.

OBJECTIVE: To ascertain the presenting symptoms of children with skeletal muscle channelopathies to promote early diagnosis and treatment. STUDY DESIGN: Retrospective case review of 38 children with a skeletal muscle channelopathy attending the specialist pediatric neuromuscular service at Great Ormond Street Hospital over a 15-year period. RESULTS: Gait disorder and leg cramps are a frequent presentation of myotonic disorders (19 of 29). Strabismus or extraocular myotonia (9 of 19) and respiratory and/or bulbar symptoms (11 of 19) are common among those with sodium channelopathy. Neonatal hypotonia was observed in periodic paralysis. Scoliosis and/or contractures were demonstrated in 6 of 38 children. School attendance or ability to engage fully in all activities was often limited (25 of 38). CONCLUSIONS: Children with skeletal muscle channelopathies frequently display symptoms that are uncommon in adult disease. Any child presenting with abnormal gait, leg cramps, or strabismus, especially if intermittent, should prompt examination for myotonia. Those with sodium channel disease should be monitored for respiratory or bulbar complications. Neonatal hypotonia can herald periodic paralysis. Early diagnosis is essential for children to reach their full educational potential.

[Neuromuscular hereditary channelopathies: non-dystrophic myotonias, paramyotonias and periodic paralysis]. / Canalopatias hereditarias neuromusculares: miotonías no distróficas, paramiotonías y parálisis periódicas.

INTRODUCTION: The ionic channels are complex glycoprotein structures, which cross the lipidic cellular membrane and allow the passage of electrically charged ions from one side of it to the other, thanks to the electrochemical gradient. A channelopathy is a disorder due to anomalous function of the ionic channels. DEVELOPMENT: In this study we analyze particularly the hereditary channelopathies with neuromuscular involvement non dystrophic myotonia, paramyotonias and periodic paralysis, and classify the clinical, physiopathological, molecular, genetic and therapeutic aspects. As far as possible we have divided the different conditions according to the channel involved, due to mutations which affect the sodium, calcium, chloride and potassium channels. We have also included neuromyotonic phenomena which are probably caused by channelopathies. CONCLUSIONS: Probably it will not be long before many of the conditions considered in this article have a better physiopathological explanation, more specific diagnostic procedures and a more rational approach to treatment.