Detecting motor unit abnormalities in amyotrophic lateral sclerosis using high-density surface EMG.
Clin Neurophysiol 2022;
142:262-272. [PMID:
35902304 DOI:
10.1016/j.clinph.2022.06.016]
[Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 06/27/2022] [Accepted: 06/30/2022] [Indexed: 12/12/2022]
Abstract
OBJECTIVE
The purpose of this study was to detect specific motor unit (MU) abnormalities in people with amyotrophic lateral sclerosis (ALS) compared to controls using high-density surface electromyography (HD-SEMG).
METHODS
Sixteen people with ALS and 16 control subjects. The participants performed ramp up and sustained contractions at 30% of their maximal voluntary contraction. HD-SEMG signals were recorded in the vastus lateralis muscle and decomposed into individual MU firing behavior using a convolution blind source separation method.
RESULTS
In total, 339 MUs were detected (people with ALS; n = 93, control subjects; n = 246). People with ALS showed significantly higher mean firing rate, recruitment threshold, coefficient of variation of the MU firing rate, MU firing rate at recruitment, and motoneurons excitability than those of control subjects (p < 0.001). The number of MU, MU firing rate, recruitment threshold, and MU firing rate at recruitment were significantly correlated with disease severity (p < 0.001). Multivariable analysis revealed that an increased MU firing rate at recruitment was independently associated with ALS.
CONCLUSIONS
These results suggest increased excitability at recruitment, which is consistent with neurodegeneration results in a compensatory increase in MU activity.
SIGNIFICANCE
Abnormal MU firing behavior provides an important physiological index for understanding the pathophysiology of ALS.
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