Stimulation of myofascial trigger points causes systematic physiological effects

Stimulation of myofascial trigger points causes systematic physiological effects

John Srbely and James P. Dickey
Purpose
Myofascial trigger points (TrP) are discrete palpable hyperirritable loci within taut bands of skeletal muscle; pressure application elicits a referral sensation/paresthesiae.1 There is growing body of evidence suggesting that a substantial proportion of common adult musculoskeletal pain syndromes are manifestations of myofascial trigger point activity.2 The possible role of neuroadaptive processes such as long-term potentiation/central sensitization, and potential management via modalities such as spinal manipulative therapy,3 is of special interest to the authors. This study will explore the neurophysiological interactions of the trigger point complex by evaluating whether stimulation of one TrP site can influence the pain sensitivity at another trigger point site innervated by the same neurological segment(s).

Methods
The study involves stimulation of a trigger point locus within the supraspinatus muscle (via intramuscular dry needling). The supraspinatus TrP will be confirmed by the presence of a visible local twitch response within the muscle, evoked during needle penetration. Raw pain-pressure threshold values (PPT) will be recorded from a trigger point site within the ipsilateral infraspinatus muscle at selected time intervals of 1, 2, 5 and 15 minutes. A baseline (pre-needling) reading will be recorded and the absolute PPT readings at each time interval (1–15 min) represented as a ratio of this baseline value.

Results
PPT readings in the infraspinatus sharply increase (i.e. decreased trigger point sensitivity) for the first two minutes post-needling. At the 2 minute mark, the PPT values tend to stabilize. Interestingly, the PPT values once again demonstrate a gradual, distinct rise between the 5 to 15 minute period, suggestive of a further decline in sensitivity at the infraspinatus site.
Conclusion
Preliminary results suggest that systematic physiological effects on a trigger point complex may be induced by stimulation of other trigger point sites specifically innervated by the same neurological level(s). This data may suggest two distinct processes at play in the neuromodulation effect: an early segmental effect which gives way to subsequent supraspinal/non-segmental effects.

References

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Boal RW. J Manipulative and Physiol Ther. 2004;27:314–326.