Near-fiber electromyography.

Area of Science:

• Neurophysiology
• Biomedical Engineering
• Clinical Electrophysiology

Background:

• Neuromuscular disorders and aging can alter motor unit (MU) morphology and electrophysiology.
• Conventional electromyography (EMG) may not detect subtle, early-stage changes.
• Near fiber electromyography (NFEMG) offers a potential method for earlier detection.

Purpose of the Study:

• To describe and evaluate near fiber electromyography (NFEMG) and its key features.
• To assess the utility of NFEMG in detecting early neuromuscular alterations.
• To introduce NFMUP segment jitter as a novel measure for neuromuscular junction (NMJ) transmission and near fiber jitter.

Main Methods:

• Extraction of near fiber motor unit potential (NFMUP) trains from needle-detected EMG signals.
• Utilizing high-pass filtered MUPs to analyze MU morphology and electrophysiology.
• Evaluation using simulated EMG data and presentation of human data examples.

Main Results:

• NFEMG features, including NFMUP duration, dispersion, and segment jitter, can detect axonal sprouting, conduction slowing, and NMJ transmission delays.
• These NFEMG measures can identify changes in MU fiber diameter variability and near fiber jitter.
• Detected changes can precede alterations in MU size or number.

Conclusions:

• NFMUP duration and dispersion correlate with distal axonal branching, conduction slowing, and NMJ transmission delay.
• NFMUP jiggle and segment jitter accurately reflect near fiber jitter.
• NFEMG demonstrates potential for augmenting the clinical diagnosis and monitoring of neuromuscular disorders through early detection of morphological and electrophysiological changes.