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Background Myofascial trigger points are commonly described in humans, and many studies have shown abnormal spontaneous electrical activity, spike activity and local twitch responses at these sites. Myofascial trigger points have only rarely been described in horses, and studies of their electrophysiological characteristics have not previously been published. The objective of this study was to explore the electromyographic (EMG) and other characteristics of myofascial trigger points in equine muscle, and to compare them with normal muscle tissue. Methods Four horses with chronic pain signs and impaired performance were examined. They had previously been examined at the second author's practice, and showed signs compatible with the diagnosis of myofascial trigger points in their cleidobrachialis (brachiocephalic) muscle, ie localised tender spots in a taut band of skeletal muscle which produced a local twitch response on snapping palpation. They had therefore been selected for treatment with acupuncture. Needle EMG activity and twitch responses were recorded at 25 positions at the trigger point and at a nearby control point during the course of each horse's acupuncture treatment. Results All subjects demonstrated objective signs of spontaneous electrical activity, spike activity and local twitch responses at the myofascial trigger point sites within taut bands. The frequency of these signs was significantly greater at myofascial trigger points than at control sites (P<0.05). Conclusion Equine myofascial trigger points can be identified, and have similar objective signs and electrophysiological properties to those documented in human and rabbit skeletal muscle tissue. The important differences from findings in human studies are that referred pain patterns and the reproduction of pain profile cannot be determined in animals.

Thermographic scanning provides an objective method of detecting sympathetic-autonomic status of vasomotor tone in the horse by imaging thermal gradients. Through observing persistent abnormal sympathetic nervous tone causing hypothermic or hyperthermic regions the clinician is able to diagnose neuromuscular disease - a common but often unrecognised cause of chronic pain and performance problems in horses. Thermography studies at the Equine Veterinary Clinic in Guildford demonstrate that acupuncture often corrects abnormal vasomotor tone within a half to three and a half hours of needling, usually resolving vasoconstriction affecting large thermatomes. Thermal imaging can provide objective, measurable evidence of the ability of acupuncture to restore normal homoeostasis in the autonomic regulation of vasomotor tone and suggests that it may simultaneously relieve associated sensorimotor disease.

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2016-12-23T18:47:23