Objectives: To determine whether the local and referred pain from active myofascial trigger points (MTrPs) reproduce the overall spontaneous fibromyalgia syndrome (FMS) pain pattern and whether widespread pressure hypersensitivity is related to the presence of widespread active MTrPs in FMS.
Methods: Forty-four women with FMS (mean age: 47±8 y) and 50 comparable healthy women (age: 48±7 y) participated in the study. MTrPs in the temporalis, masseter, upper trapezius, splenius capitis, sternocleidomastoid, suboccipital, levator scapulae, scalene, pectoralis major, extensor carpi radialis brevis, extensor digitorum communis, gluteus maximus, piriformis, vastus medialis, and tibialis anterior muscles were explored. Pressure pain thresholds over 18 tender points specified in the 1990 American College of Rheumatology for FMS were also assessed by an assessor blinded to the condition of the participants.
Results: The mean±SD number of MTrPs for each woman with FMS was 11±3, of which 10±2 were active MTrPs and the remaining 1±1 were latent. Healthy controls only had latent MTrPs (mean±SD: 2±1). The combination of the referred pain patterns from active MTrPs fully reproduced the overall spontaneous clinical pain area in patients with FMS. Patients with FMS had significant lower PPT compared with controls (P<0.001). Within FMS, a significant positive correlation was found between the number of active MTrPs and spontaneous pain intensity (rs=0.455; P=0.002).
Conclusions: The local and referred pain elicited from widespread active MTrPs fully reproduced the overall spontaneous clinical pain area in patients with FMS. Widespread mechanical pain hypersensitivity was related to a greater number of active MTrPs. This study suggests that nociceptive inputs from active MTrPs may contribute to central sensitization in FMS.