Detecting motor unit abnormalities in amyotrophic lateral sclerosis using high-density surface EMG.

Area of Science:

• Neurology
• Neurophysiology
• Biomedical Engineering

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting motor neurons.
• Understanding motor unit (MU) dysfunction is crucial for diagnosing and managing ALS.
• High-density surface electromyography (HD-SEMG) offers advanced insights into MU behavior.

Purpose of the Study:

• To identify specific motor unit (MU) abnormalities in individuals with ALS compared to healthy controls.
• To utilize high-density surface electromyography (HD-SEMG) for detecting these abnormalities.

Main Methods:

• HD-SEMG signals were recorded from the vastus lateralis muscle in 16 ALS patients and 16 controls during voluntary contractions.
• Motor unit (MU) firing behavior was analyzed using a convolution blind source separation method.
• Key parameters including firing rate, recruitment threshold, and excitability were assessed.

Main Results:

• A total of 339 MUs were analyzed (93 in ALS, 246 in controls).
• Individuals with ALS demonstrated significantly higher mean firing rate, recruitment threshold, coefficient of variation of MU firing rate, MU firing rate at recruitment, and motoneuron excitability (p < 0.001).
• Increased MU firing rate at recruitment was independently associated with ALS, and these parameters correlated with disease severity.

Conclusions:

• The findings suggest increased motoneuron excitability at recruitment in ALS patients.
• This heightened excitability likely represents a compensatory increase in MU activity in response to neurodegeneration.
• Abnormal MU firing behavior serves as a significant physiological marker for ALS pathophysiology.