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A congenital myasthenic syndrome refractory to acetylcholinesterase inhibitors
Author(s) -
Triggs William J.,
Beric Aleksandar,
Butler Ian J.,
Roongta Suresh M.
Publication year - 1992
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880150302
Subject(s) - repetitive nerve stimulation , edrophonium , neuromuscular transmission , medicine , congenital myasthenic syndrome , electromyography , neuromuscular junction , stimulation , anesthesia , weakness , compound muscle action potential , refractory period , acetylcholinesterase , myasthenia gravis , anatomy , neuroscience , electrophysiology , psychology , acetylcholine receptor , physical medicine and rehabilitation , chemistry , enzyme , biochemistry , receptor
We studied 4 siblings (3 men and 1 woman), ages 22 to 43 years, with congenital ptosis, external ophthalmoplegia, proximal muscle weakness and fatigability unresponsive to acetylcholinesterase (AChE) inhibitors. Repetitive nerve stimulation showed a significant compound muscle action potential (CMAP) area decrement at 2 or 3 Hz. Nerve conduction studies and concentric needle electromyography were normal, and repetitive CMAPs to single nerve stimulation were not observed. Voluntary single fiber electromyography (SFEMG) showed increased jitter and blocking. Assessment of individual end‐plates using SFEMG with intramuscular axonal microstimulation showed no uniform relationship between jitter and the rate of stimulation, consistent with a postsynaptic defect of neuromuscular transmission. Edrophonium eliminated the decremental response to repetitive nerve stimulation, but caused no significant clinical improvement, suggesting an additional mechanism for weakness in these patients.