Document Detail

Motor neuron firing dysfunction in spastic patients with primary lateral sclerosis.
MedLine Citation:
PMID:  15829597     Owner:  NLM     Status:  MEDLINE    
Patients with corticospinal tract dysfunction have slow voluntary movements with brisk stretch reflexes and spasticity. Previous studies reported reduced firing rates of motor units during voluntary contraction. To assess whether this firing behavior occurs because motor neurons do not respond normally to excitatory inputs, we studied motor units in patients with primary lateral sclerosis, a degenerative syndrome of progressive spasticity. Firing rates were measured from motor units in the wrist extensor muscles at varying levels of voluntary contraction < or =10% maximal force. At each force level, the firing rate was measured with and without added muscle vibration, a maneuver that repetitively activates muscle spindles. In motor units from age-matched control subjects, the firing rate increased with successively stronger contractions as well as with the addition of vibration at each force level. In patients with primary lateral sclerosis, motor-unit firing rates remained stable, or in some cases declined, with progressively stronger contractions or with muscle vibration. We conclude that excitatory inputs produce a blunted response in motor neurons in patients with primary lateral sclerosis compared with age-matched controls. The potential explanations include abnormal activation of voltage-activated channels that produce stable membrane plateaus at low voltages, abnormal recruitment of the motor pool, or tonic inhibition of motor neurons.
Mary Kay Floeter; Ping Zhai; Rajiv Saigal; Yongkyun Kim; Jeffrey Statland
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Publication Detail:
Type:  Comparative Study; Journal Article     Date:  2005-04-13
Journal Detail:
Title:  Journal of neurophysiology     Volume:  94     ISSN:  0022-3077     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  2005 Aug 
Date Detail:
Created Date:  2005-08-02     Completed Date:  2005-09-22     Revised Date:  2013-06-09    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  919-27     Citation Subset:  IM    
Electromyography Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1404, USA.
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MeSH Terms
Action Potentials / physiology*
Case-Control Studies
Electromyography / methods
Middle Aged
Motor Neuron Disease / complications*
Motor Neurons / physiology*
Muscle Contraction / physiology
Muscle Spasticity / etiology,  physiopathology*
Muscle, Skeletal / pathology*
Physical Stimulation / methods
Sensory Thresholds / physiology
Grant Support
Z01 NS002976-07/NS/NINDS NIH HHS

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