Neuromuscular Junction and Muscle

Neuromuscular Transmission Defects

Neuromuscular transmission defects present with weakness and fatigability. The tendency to fatigue early and the absence of sensory symptoms are clues to these disorders.

These defects are due to impaired synaptic transmission, either from impaired acetylcholine (ACh) release from the presynaptic terminal or reduced available ACh receptors (AChRs) on the postsynaptic terminal. The essential features of the major neuromuscular transmission defects are shown in Chapter 5.5 .

Myasthenia gravis is an autoimmune disorder that presents with weakness that often involves ocular motor function but then extends to involve other muscle groups, including bulbar and respiratory muscles.

Botulism is due to poisoning with the botulinum toxin and is suspected when a patient presents with rapidly progressive weakness and is found to have had recent abdominal complaints, even if there is no known etiology for the toxin entry.

Myasthenic (Eaton-Lambert) syndrome is an autoimmune disorder and is often paraneoplastic. It is suspected when a patient presents with weakness and autonomic symptoms including dry mouth.