RESUMO
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.
Assuntos
Anestesia , Miotonia , Transtornos Miotônicos , Feminino , Humanos , Adulto Jovem , Adulto , Succinilcolina/efeitos adversos , Força da Mão , Transtornos Miotônicos/induzido quimicamente , Transtornos Miotônicos/diagnóstico , Miotonia/induzido quimicamente , Miotonia/genética , Canal de Sódio Disparado por Voltagem NAV1.4/genéticaAssuntos
Inibidores de Hidroximetilglutaril-CoA Redutases/efeitos adversos , Miotonia/induzido quimicamente , Rabdomiólise/induzido quimicamente , Sinvastatina/efeitos adversos , Idoso , Eletromiografia , Feminino , Humanos , Inibidores de Hidroximetilglutaril-CoA Redutases/uso terapêutico , Hipercolesterolemia/tratamento farmacológico , Miotonia/fisiopatologia , Agulhas , Rabdomiólise/diagnóstico , Rabdomiólise/fisiopatologia , Sinvastatina/uso terapêuticoAssuntos
Idoso , Feminino , Humanos , Inibidores de Hidroximetilglutaril-CoA Redutases/efeitos adversos , Miotonia/induzido quimicamente , Rabdomiólise/induzido quimicamente , Sinvastatina/efeitos adversos , Eletromiografia , Inibidores de Hidroximetilglutaril-CoA Redutases/uso terapêutico , Hipercolesterolemia/tratamento farmacológico , Miotonia/fisiopatologia , Agulhas , Rabdomiólise/diagnóstico , Rabdomiólise/fisiopatologia , Sinvastatina/uso terapêuticoRESUMO
Experimental myotonia was induced in rats by 2,4-dichloro-phenoxyacetic acid (2,4-D). After 4 to 24 h of treatment, the anterior tibialis muscles exhibited increased fatigue at low frequency (30 Hz) nerve stimulation, but they developed normal tension at high-frequency (100 Hz) stimulation. Glycogen content and the activities of glycogen phosphorylase, lactate dehydrogenase and malate dehydrogenase remained normal. The absence of correlation between fatigability and energetic metabolism in this experimental model of myotonia suggests a dysfunction in excitation-contraction coupling.
Assuntos
Metabolismo Energético , Contração Muscular/efeitos dos fármacos , Miotonia/metabolismo , Ácido 2,4-Diclorofenoxiacético , Animais , Modelos Animais de Doenças , Eletromiografia , Injeções Intraperitoneais , L-Lactato Desidrogenase/metabolismo , Malato Desidrogenase/metabolismo , Masculino , Miotonia/induzido quimicamente , Fosforilases/metabolismo , Ratos , Ratos Sprague-Dawley , Estimulação Química , Fatores de TempoAssuntos
Ratos , Animais , Masculino , Contração Muscular/efeitos dos fármacos , Miotonia/metabolismo , Ácido 2,4-Diclorofenoxiacético , Modelos Animais de Doenças , Eletromiografia , Malato Desidrogenase/metabolismo , Miotonia/induzido quimicamente , Miotonia/enzimologia , Fosforilases/metabolismo , Ratos Wistar , Estimulação Química , Fatores de TempoRESUMO
The relation between resistance to fatigue and intramuscular pH was studied in fast muscles (anterior tibialis and extensor digitorum longus) from rats treated with 2,4-dichlorophenoxyacetic acid (2,4-D) to induce myotonia. Fatiguability was studied in muscles indirectly stimulated at 30 Hz (330 ms/s; 1 train/s) for 2 min. The resistance to fatigue decreased significantly 1 h after drug treatment and remained low 24 h later. The intramuscular pH was lower than normal in resting muscles from 2,4-D-treated rats. After 2 min of stimulation the pH decreased in both control and drug-treated muscles. However, this decrement was reduced in the experimental muscles. The pH of control and of 2,4-D-treated muscles were similar after the stimulation period, but only the drug-treated muscles were fatigued. Therefore, a decrease in intramuscular pH would not be the cause of the observed decrease in muscle resistance to fatigue after 2,4-D treatment. The reduced endurance of drug-treated muscles could not be attributed to impaired neuromuscular transmission.