Neuromuscular transmission in myasthenic single motor units

In patients with myasthenia gravis neuromuscular transmission has been tested in individual hypothenar and thenar motor units using trains of near threshold electrical stimuli delivered to the motor nerve. The most important observations included: (1) the proportion of motor units with pathological...

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Bibliographic Details
Published in:Journal of neurology, neurosurgery and psychiatry neurosurgery and psychiatry, 1978-03, Vol.41 (3), p.205-214
Main Authors: Kadrie, H A, Brown, W F
Format: Article
Language:English
Subjects:
Action Potentials - drug effects
Adolescent
Adult
Aged
Edrophonium - pharmacology
Electric Stimulation
Electromyography
Female
Humans
Male
Median Nerve - physiopathology
Middle Aged
Muscles - innervation
Myasthenia Gravis - physiopathology
Neuromuscular Junction - physiopathology
Recruitment, Neurophysiological - drug effects
Refractory Period, Electrophysiological - drug effects
Synaptic Transmission - drug effects
Ulnar Nerve - physiopathology
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Summary:In patients with myasthenia gravis neuromuscular transmission has been tested in individual hypothenar and thenar motor units using trains of near threshold electrical stimuli delivered to the motor nerve. The most important observations included: (1) the proportion of motor units with pathological decrements varied from 0 to 90%, (2) the decrements in surface voltage were frequently much more normal in individual motor units than in the corresponding maximum compound potentials evoked by supramaximal nerve stimulation, and (3) the most abnormal decrements were observed in motor units at the low end of the surface voltage range. These observations can be interpreted to suggest important neurogenic factors in the pathogenesis of myasthenia gravis. An attractive alternative would be to suggest that the small motor units have the most abnormal neuromuscular transmission because they normally have a lower margin for safe neuromuscular transmission and, as a consequence, fail first in diseases of neuromuscular transmission.
ISSN:0022-3050
1468-330X
DOI:10.1136/jnnp.41.3.205