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Repetitive CMAPs: Mechanisms of neural and synaptic genesis
Author(s) -
van Dijk J. Gert,
Lammers Gert Jan,
Wintzen Axel R.,
Molenaar Peter C.
Publication year - 1996
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/(sici)1097-4598(199609)19:9<1127::aid-mus7>3.0.co;2-1
Subject(s) - refractory period , synapse , neuromuscular junction , anatomy , neuroscience , repetitive nerve stimulation , medicine , chemistry , electromyography , anesthesia , biology
Repetitive compound muscle action potentials (R‐CMAPs) occur when a single nerve shock excites muscle fibers repeatedly. “Double discharges” are due to intramuscular nerve reexcitation. “Synaptic” R‐CMAPs, due to excess acetylcholine in the neuromuscular synapse, can occur in congenital myasthenia, the slow‐channel syndrome, and acetylcholinesterase inhibition. Secondary nerve excitation can reexcite muscle fibers. Synaptic R‐CMAPs in a patient consisted of two discharges. The second diminished during repetitive stimulation and began 3.5–4.0 ms after the first, which is slightly longer than the synapse‐muscle refractory period. Neural R‐CMAPs, due to ectopic nerve activity, occur in neuromyotonia (NMT). R‐CMAPs in a patient consisted of about 20 discharges at 200–300 Hz. Studies in healthy subjects showed that such trains represent added single CMAPs. Impulse frequency in the patient lies close to the threshold of refractoriness. Refractoriness of the synapse‐muscle cell assembly determines the characteristics of R‐CMAPs regardless of the primary cause. © 1996 John Wiley & Sons, Inc.