Disorders of the Neuromuscular Junction

The chapter begins with a general discussion of synapses and their neurotransmitters. In humans, all nerve to nerve, nerve to muscle, and peripheral sensory receptor to nerve communication occurs via synapses. An electrical signal traveling along a nerve axon is converted at a specialized nerve ending called a synapse. There are at least 30 different neurotransmitters, with the greatest number occurring in the CNS. Neurotransmitters are classified into simple chemicals (acetylcholine, norepinephrine, dopamine), amino acids (gamma amino butyric acid [GABA], glycine, glutamine), or peptides (substance P, endorphins). Next, the chapter discusses pathological diseases of the synapse called synaptopathies, which may occur from chemical or biologic toxins, antibodies directed against synaptic receptor molecules, or genetic mutations in the synaptic receptor or membrane channel. The major synaptopathies, myasthenia gravis, Lambert–Eaton myasthenic syndrome, and botulism, are reviewed with attention to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.