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Abnormal single motor unit behavior in the upper motor neuron syndrome
Author(s) -
Shahani Bhagwan T.,
Wierzbicka Margaret M.,
Parker Stephen W.
Publication year - 1991
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.880140111
Subject(s) - upper motor neuron , precentral gyrus , biceps , hyperreflexia , lesion , lower motor neuron , motor unit , medicine , motor neuron , magnetic resonance imaging , anatomy , psychology , neuroscience , amyotrophic lateral sclerosis , anesthesia , pathology , radiology , spinal cord , disease
We studied the discharge pattern of single motor units (SMUs) in the left and right biceps muscles from a patient with nonspastic weakness of the left arm. Detailed statistical analysis of the behavior of discharge patterns of 4 of 4 single motor units on the affected side showed abnormalities with characteristic features of an upper motor neuron lesion. Five out of 5 single motor units recorded from the right biceps were normal. An upper motor neuron lesion affecting the left arm, predicted by our results, was confirmed by magnetic resonance imaging (MRI), which showed a lesion in the right precentral gyrus. It appears that changes in single motor unit firing characteristics, caused by an upper motor neuron lesion, can be detected at a time when there is no evidence of increased “tone” and/or hyperreflexia (spasticity) in the affected extremity.