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Myofascial trigger points show spontaneous needle EMG activity
1Department of Neurosciences, University of California, San Diego.
Spine
|October 1, 1993
Summary
Spontaneous electrical activity was detected in the trigger points (TrPs) of the trapezius muscle in patients with tension headaches and fibromyalgia. This finding suggests a link between these trigger points and sympathetic nervous system activity.
Area of Science:
- Neurology
- Pain Medicine
- Musculoskeletal Disorders
Background:
- Myofascial trigger points (TrPs) are associated with chronic pain conditions.
- The underlying physiological mechanisms of TrPs remain incompletely understood.
Purpose of the Study:
- To investigate the electromyographic (EMG) activity within trapezius myofascial trigger points (TrPs) and adjacent non-trigger points (non-TrPs).
- To compare EMG activity in normal subjects with patients suffering from tension headache and fibromyalgia.
Main Methods:
- Simultaneous monopolar needle electromyogram (EMG) recordings were performed.
- EMG activity was measured from trapezius TrPs and non-TrPs in normal subjects, tension headache patients, and fibromyalgia patients.
Main Results:
- Sustained spontaneous EMG activity was consistently found in the nidus (1-2 mm) of all TrPs.
- This spontaneous activity was absent in the non-TrPs of the same muscles.
- Mean EMG amplitude was significantly higher in the patient groups (tension headache and fibromyalgia) compared to normal subjects.
Conclusions:
- The study provides evidence for distinct, sustained spontaneous electromyographic activity within myofascial trigger points.
- These findings support the hypothesis that TrPs may be caused by sympathetically activated intrafusal muscle contractions.
- This research offers potential insights into the pathophysiology of tension headache and fibromyalgia.