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Single motor unit variability with threshold stimulation in patients with amyotrophic lateral sclerosis and normal subjects
Author(s) -
Jillapalli Devanand,
Shefner Jeremy M.
Publication year - 2004
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.20147
Subject(s) - amyotrophic lateral sclerosis , motor unit , stimulation , medicine , electromyography , confounding , degenerative disease , physical medicine and rehabilitation , neuroscience , central nervous system disease , audiology , psychology , disease , anatomy
Repetitive nerve stimulation often shows responses with an abnormal decrement in patients with amyotrophic lateral sclerosis (ALS), suggesting instability of the neuromuscular junction; however, the pathophysiology and response characteristics of this instability are not clear. We evaluated response variability of 47 single motor units from 16 patients with ALS and 51 units from 10 normal subjects, acquired by delivering threshold stimuli sporadically at 0.5 H Z or less. In addition, in 46 other different single motor units obtained from 21 patients with ALS, variability was studied at both 1‐ and 3‐H Z stimulation rates. Motor units from patients with ALS were significantly more variable than those from normal subjects, even when their larger amplitude was accounted for. This increased variability was not rate dependent. Response variability is a critical measure in the statistical method of motor unit number estimation and is attributed to variability in the number of units activated; the fact that variability of single motor units varies with disease state may be a potentially confounding factor in the application of the technique. Muscle Nerve, 2004