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Patterns of Motoneuron Dysfunction and Recovery

Published online by Cambridge University Press:  18 September 2015

Alan McComas ,
Adrian Upton  and
Per Jorgensen
Alan McComas*
Affiliation:
Medical Research Council’s Developmental Neurobiology Research Group and the Department of Medicine, McMaster University Medical Center, 1200 Main St. W., Hamilton, Ontario
Adrian Upton
Affiliation:
Medical Research Council’s Developmental Neurobiology Research Group and the Department of Medicine, McMaster University Medical Center, 1200 Main St. W., Hamilton, Ontario
Per Jorgensen
Affiliation:
Medical Research Council’s Developmental Neurobiology Research Group and the Department of Medicine, McMaster University Medical Center, 1200 Main St. W., Hamilton, Ontario
*
McMaster University Medical Center, 1200 Main St. W, Hamilton, Ontario
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Electrophysiological studies have been carried out on five patients with neuropathies of different etiologies. In each patient serial estimates were made of the numbers of functioning motor units in various muscles. It was found that the intensity of the neuropathic process and the rate of recovery differed in a consistent way among the motoneuron pools investigated. The lesion was more severe in extensor digitorum brevis neurons than in thenar neurons, while the hypothenar ones were least affected. A stage of partial synaptic failure has been recognized in which a motoneuron appears to be no longer able to excite a muscle fiber, but still capable of maintaining certain trophic activities. By comparing the number of functioning motor units with the size of the maximum evoked muscle response it has been possible to detect the adoption of denervated muscle fibers by axonal sprouts from ‘healthy’ surviving neurons (collateral reinnervation). Lastly, in some muscles it appears that the adopted muscle fibers may subsequently be recaptured by the original motoneurons following recovery of the latter from the neurotoxic insult.

Type
Research Article
Information
Canadian Journal of Neurological Sciences , Volume 2 , Issue 1 , February 1975 , pp. 5 - 15
Copyright
Copyright © Canadian Neurological Sciences Federation 1975

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