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Relation between maximum discharge rates on electromyography and motor unit number estimates
W J Schulte-Mattler1, D Georgiadis, K Tietze
1Neurologische Klinik und Poliklinik, Martin-Luther-Universität, Halle-Wittenberg, Ernst-Grube-Strasse 40, D-06097 Halle, Germany. wilhelm.schulte-mattler@medizin.uni-halle.de
Muscle & Nerve
|January 20, 2000
Summary
Maximal motor unit discharge rate in electromyography (EMG) can indicate motor unit loss. High discharge rates in hypothenar muscles suggest denervation, providing an estimate of motor unit number.
Area of Science:
- Neurology
- Neurophysiology
- Biomedical Engineering
Background:
- Quantitative assessment of motor unit recruitment in electromyography (EMG) requires improvement.
- Standard concentric needle electromyography (CNEMG) is a common diagnostic tool.
Purpose of the Study:
- To evaluate the utility of maximal motor unit discharge rate for assessing motor unit loss.
- To explore the correlation between motor unit number and maximal discharge rate.
Main Methods:
- Conducted CNEMG on hypothenar muscles of healthy subjects, patients with denervation, and patients with myopathy.
- Measured motor unit discharge rates and performed motor unit number estimation (MUNE) using the manual incremental method.
Main Results:
- A strong nonlinear correlation (r = 0.88) was observed between motor unit number and maximal discharge rate.
- Increased discharge rates were noted in most paretic muscles with denervation but not in myopathic muscles.
- The upper 95% limit of discharge rate in controls was 16.2/s.
Conclusions:
- Maximal motor unit discharge rate is a simple, reliable indicator of motor unit loss.
- Elevated discharge rates in hypothenar muscles can infer motor unit loss and estimate the remaining motor units.
- Recommends incorporating maximal discharge rate into routine electromyographic reports.