title: ["Fatiguability" in myasthenic syndromes].
abstract: Neuromuscular disorders accompanied by a "myasthenic reaction", but without other symptoms of myasthenia gravis and no therapeutic response to cholinergic drugs may be called myasthenic syndromes. The abnormal fatigability can be shown in the electromyogram. Lasting voluntary contraction of a muscle shows a rarefication of the EMG-pattern. Sometimes during repetitive stimulation of the motor nerve a decrease in the amplitude of the muscle potential may occur. This decrease is poorly influenced by cholinergic drugs. Often this observation was present in patients with myositis and myotonic dystrophy, sometimes in other myopathies and seldom in neurogenic disorders. A failure in the neuromuscular transmission is discussed not only in myasthenia gravis, but also in myasthenic syndromes. But there may be another explanation. A decreased number of intact muscle fibers during lasting innervation will cause a more rapid fatigation of the muscle fibers and in this way there will be an exhaustion. It is discussed, whether the symptoms in myasthenic syndromes can be explained by an abnormal "fatigability".
mesh_terms: D000293:Adolescent; D003937:Diagnosis, Differential; D004576:Electromyography; D005260:Female; D006801:Humans; D009119:Muscle Contraction; D009135:Muscular Diseases / Q000175:diagnosis / Q000503:physiopathology*; D009157:Myasthenia Gravis / Q000175:diagnosis; D009469:Neuromuscular Junction / Q000503:physiopathology*
vernacular_title: "Ermüdungsreaktion" bei myasthenischen Syndromen