Disorders of Neuromuscular Transmission

Most disorders of neuromuscular transmission (NMT) are autoimmune diseases, including myasthenia gravis (MG) and the less common Lambert-Eaton myasthenic syndrome (LEMS). Toxic/infectious causes, such as botulism, and genetic disorders, such as congenital myasthenic syndromes, are rare. In contrast to most other neuromuscular diseases, most NMT disorders cause early weakness of ocular and other cranial muscles. Because they can lead to life-threatening bulbar and respiratory muscle weakness and they are generally treatable, either with immunotherapy (MG, LEMS) or antitoxin treatment (botulism), their prompt recognition is of critical importance. The principles of diagnosis by serum antibody and electrophysiologic testing, including repetitive nerve stimulation and single-fiber EMG, and the principles of symptomatic and disease-specific treatment of those conditions, are summarized in this chapter.