Objective: To investigate somato-sensory nerve fibre function by applying different quantitative sensory testing including thermal, mechanical and vibration thresholds over latent trigger points (TrP) and in its associated referred pain area.
Methods: A total of 20 subjects with unilateral latent TrPs in the extensor carpi radialis brevis were included. Warmth detection threshold (WDT), cold detection threshold CDT) and heat/cold pain thresholds (HPT, CPT), mechanical detection (MDT) and pain (MPT) thresholds, vibration threshold (VT), and pressure pain thresholds (PPT) were blinded assessed over the TrP, in the referred pain area, and in the respective contra-lateral mirror areas. A multilevel mixed-model ANOVA with site (TrP, referred pain area) and side (real or contra-lateral) as within-subjects factors and gender as between-subjects factor was conducted.
Results: No significant differences for thermal detection (WDT, CDT) or thermal pain thresholds (HPT, CPT) were found (all, P>0.141). The assessments over the TrP area showed lower PPT and MDT compared to the mirror contra-lateral TrP area (P<0.05). MDT were higher (P=0.001) but PPT (P<0.001) and MPT (P=0.032) were lower over the TrP area and contra-lateral mirror point compared to their respectively referred pain areas. Finally, VT was higher over the TrP area than in the referred pain area and over both mirror contra-lateral points.
Discussion: Assessing sensory changes over latent myofascial TrPs reveal mechanical hyperesthesia, pressure pain hyperalgesia, and vibration hypoesthesia compared to a contra-lateral mirror area.
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