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Quantitative EMG in cervical dystonia
L Ostergaard1, A Fuglsang-Frederiksen, O Sjö
1Department of Neurology, Hvidovre Hospital, University of Copenhagen, Denmark.
Electromyography and Clinical Neurophysiology
|April 1, 1996
Summary
Botulinum toxin A injections are key for cervical dystonia. This study reveals abnormal EMG activity in neck muscles, even seemingly unaffected ones, impacting treatment guidance.
Area of Science:
- Neurology
- Biomedical Engineering
Background:
- Cervical dystonia treatment increasingly uses botulinum toxin A (BT).
- Electromyography (EMG) guides BT injections, necessitating deeper understanding of muscle electrical activity.
- Quantitative EMG analysis can reveal subtle muscle changes in cervical dystonia.
Purpose of the Study:
- To quantitatively evaluate electromyographic (EMG) changes in neck muscles of cervical dystonia patients using turns-amplitude analysis.
- To compare EMG findings with clinical presentation and identify patterns of muscle involvement.
Main Methods:
- Turns-amplitude analysis of EMG signals from sternocleidomastoid and posterior neck muscles.
- Inclusion of 44 treatment-naive cervical dystonia patients and 12 healthy controls.
- Assessment of resting and voluntary contraction EMG activity.
Main Results:
- Abnormal resting EMG activity (>100 turns/s) was detected in various neck muscle combinations in most patients.
- Clinical examination did not always predict the distribution of abnormal muscle activity.
- Reduced EMG activity during maximal voluntary contraction in apparently unaffected muscles (CPN, IS) suggests impaired motor unit activation.
Conclusions:
- Quantitative EMG analysis reveals widespread, often clinically unexpected, muscle abnormalities in cervical dystonia.
- Findings highlight the utility of EMG in guiding botulinum toxin A injections by identifying affected muscles.
- Impaired voluntary activation in seemingly normal muscles warrants further investigation in cervical dystonia pathophysiology.