Neuromuscular transmission syndromes

Neuromuscular blockade. Aminoglycosides may impair neuromuscular transmission and aggravate (or reveal) myasthenia gravis, or cause a transient myasthenic syndrome in patients whose neuromuscular transmission is normal. 

Buchwald B, Weishaupt A, Toyka KV, Dudel J (1998) Pre- and post-synaptic blockade of neuromuscular transmission by MiUer-Fisher syndrome IgG at mouse motor nerve terminals. Eur J Neurosci 10 281-290. 

While the exact cause of muscle weakness was unclear, this case argues against the use of botulinum toxin in patients with myasthenic syndromes. When the margin of safety is reduced with regard to neuromuscular transmission, botulinum toxin can result in increased morbidity or even mortality. Generalized muscle weakness after botulinum toxin has also been reported in patients with other neuromuscular disorders (18). In addition, it should be remembered that both dysphagia and muscle weakness can occur after botulinum toxin injection, even in patients who do not suffer from generalized neuromuscular disorders (19). 

Acute encephalopathy (cholinergic syndrome) neuromuscular transmission dysfunction acetylcholinesterase inhibition... 

Skin rashes occur in approximately 10% of patients treated with clindamycin, and may be more common in patients with HIV infection. Other reactions, which are uncommon, include exudative erythema multiforme (Stevens-Johnson syndrome), reversible elevation of aspartate aminotransferase and alanine aminotransferase, granulocytopenia, thrombocytopenia, and anaphylactic reactions. Local thrombophlebitis may follow intravenous administration of the drug. Clindamycin can inhibit neuromuscular transmission and may potentiate the effect of a neuromuscular blocking agent administered concurrently. 

Fig. 6.6 Characteristics of neuromuscular response following repeated nerve stimulation. Depolarisation block, with no fade, is characteristic of failure of neuromuscular transmission in the cholinergic syndrome produced by antichohnesterase compounds such as sarin...

The degree of recorded jitter in SFEMG is directly related to the release of ACh and the function of the ACh receptors in the NMJ. SFEMG therefore provides a window into the operation of the NMJ. Jitter is characteristically increased in conditions (both pre- and post-junctional) of the NMJ which reduce the safety margins of neuromuscular transmission. Thus, there is increased jitter in conditions such as myasthenia gravis and Lambert-Eaton syndrome. Jitter is also increased following the administration of small doses... 

Central Serotonin Syndrome is manifest by autonomic, neuromuscular, and cognitive symptoms. Mild symptoms can include tremor, incoordination, and confusion. Moderate symptoms can manifest as shivering, sweating, hyperreflexia, and agitation, and severe symptoms include fever, myoclonus, and diarrhea. This syndrome is usually associated with two or more drugs that increase central serotonin transmission and affect the 5-HTia receptor (see Table 5.4). 

Myasthenia gravis is a neurological disease of autoimmune origin. The basic defect is the reduction of ificotinic acetylcholine receptors (AChR) at the neuromuscular junction, resulting in inadequate transmission through the neuromuscular junction and hence the clinical syndrome of weakness, frequently worsened by exercise or effort. 

One of the clinical signs associated with MeHg intoxication is a myasthenia gravis-like muscle weakness in adults (Rustam et al. 1975), a syndrome which responded well to therapy with neostigmine, a reversible acetylcholinesterase inhibitor. In this syndrome, two effects of MeHg on synaptic transmission at the neuromuscular junction were demonstrated using intracellular microelectrode recording techniques (Atchison and Narahashi 1982 Atchison et al. 1984). First, nerve-evoked, synchronous quantal release of acetylcholine (ACh) is inhibited, as indicated by a decrease in end-plate potential (EPP) amplitude. Second, spontaneous quantal release... 

---