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Updated size index valid for both neurogenic and myogenic changes
Masahiro Sonoo1, Go Ogawa1, Keiichi Hokkoku1
1Department of Neurology, Teikyo University School of Medicine, Tokyo, Japan.
Muscle & Nerve
|September 17, 2020
Summary
The size index (SI) effectively distinguishes neurogenic motor unit potentials (MUPs) and shows promise for myogenic MUPs in electromyography. A revised SI (rSI) offers comparable sensitivity for neurogenic MUPs.
Area of Science:
- Neurology
- Electromyography
- Motor Unit Potential Analysis
Background:
- The size index (SI) is a motor unit potential (MUP) parameter used in concentric needle electromyography.
- SI is calculated from amplitude and area/amplitude, effectively discriminating between control and neurogenic MUPs.
Purpose of the Study:
- To investigate the application of SI to myogenic MUPs using expanded datasets.
- To evaluate a revised SI (rSI) incorporating a logarithmic scale for area/amplitude.
Main Methods:
- MUPs were collected from biceps brachii (BB) and tibialis anterior (TA) muscles.
- A revised SI (rSI) was defined using a logarithmic scale for area/amplitude, with optimized coefficients.
- Muscles with clear neurogenic or myogenic changes were selected for analysis.
Main Results:
- For neurogenic MUPs, SI and rSI demonstrated high sensitivity (e.g., 82.1% for SI in BB) exceeding conventional parameters like area.
- For myogenic MUPs, the revised SI (rSIm) showed sensitivity (e.g., 24.5% in TA) comparable to duration.
Conclusions:
- The size index (SI), including its revised form (rSI), shows potential as a novel parameter for MUP analysis.
- SI demonstrates effectiveness in differentiating neurogenic MUPs and emerging utility for myogenic MUPs.
