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Muscle surface mechanical and electrical activities in myotonic dystrophy
C Orizio1, F Esposito, V Sansone
1Department of Biomedical Sciences and Biotechnologies, University of Brescia, Italy.
Electromyography and Clinical Neurophysiology
|June 1, 1997
Summary
Mechanomyogram (MMG) and surface electromyography (EMG) signals reveal reduced muscle force and electromechanical coupling efficiency (EMCE) in myotonic dystrophy (DM) patients. This non-invasive technique can monitor disease progression.
Area of Science:
- Neurology
- Biomedical Engineering
- Muscle Physiology
Background:
- Muscle fiber dimensional changes generate mechanomyogram (MMG) signals.
- Electromyography (EMG) and MMG assess motor unit activity.
- Myotonic dystrophy (DM) is a progressive muscle disorder.
Purpose of the Study:
- To evaluate if root mean square (RMS) of surface EMG, MMG, and their relationship (electromechanical coupling efficiency, EMCE) correlate with the clinical stage in myotonic dystrophy patients.
- To compare these measures between less affected (elbow flexors, EF) and more affected (finger flexors, FF) muscles in DM patients and healthy controls.
- To assess the utility of MMG and EMG in monitoring dystrophic changes.
Main Methods:
- Recorded surface EMG and MMG during isometric contractions at 20%, 40%, and 60% of maximal voluntary contraction (MVC).
- Studied 10 DM patients (disease duration 15-22 yr, MDRS scale 3-4) and 10 age-matched controls.
- Analyzed MVC, MMG-RMS, EMG-RMS, and EMCE in EF and FF muscles.
Main Results:
- Maximal voluntary contraction (MVC) was significantly lower in DM patients' finger flexors (FF) but not elbow flexors (EF).
- MMG-RMS and EMG-RMS were significantly lower in DM patients compared to controls at equivalent relative forces.
- Electromechanical coupling efficiency (EMCE) was dramatically reduced in the more affected FF muscles of DM patients.
Conclusions:
- Changes in EMCE due to the dystrophic process in myotonic dystrophy can be monitored using non-invasive EMG and MMG techniques.
- These findings demonstrate a strong correlation between clinical observations and experimental results.
- MMG and EMG offer a promising method for assessing disease progression and treatment efficacy in myotonic dystrophy.