Muscle Pressure Correlates With Pain Levels in Fibromyalgia Patients

We evaluated patients with fibromyalgia syndrome (FMS) to determine whether there is a correlation between pain scores based on a 0- to 10-point visual analog scale (VAS) and muscle pressure.

One hundred forty-two patients who satisfied the American College of Rheumatology classification criteria for FMS and 38 non-FMS controls comprised the study groups. Muscle pressure was measured in mm Hg using a pressure gauge attached to a no. 22 needle inserted into the midportion of the trapezius muscle. The muscle pressure was then correlated with the VAS pain score of 0 to 10, some with an increment of 0.5. A second muscle pressure was obtained from 19 patients at a subsequent visit, which was compared with their pain scores.

The mean (SD) pain score for 142 patients with FMS was 6.6 (SD, 1.84) on a 0- to 10-point VAS. The mean pain score in the non-FMS subjects was 0.7 (SD, 1.26). The mean muscle pressure in the FMS group was 32.9 (SD, 6.57) mm Hg. The mean muscle pressure in the non-FMS subjects was 10.6 (SD, 3.85) mm Hg. The calculated Pearson correlation coefficient for muscle pressure versus pain score was 0.8312 ( p < 0.0001). This indicates a highly significant association between subjects' muscle pressure and pain scores. For the repeat muscle pressures, the change in muscle pressure was correlated with the change in pain score, and the resulting Pearson correlation coefficient was 0.9255 ( p < 0.0001). These results again indicate a highly significant association between subjects' muscle pressure and pain scores.

The results show that increased muscle pressure may be a significant cause of pain in FMS, and the etiology of the pain may have a large peripheral component in addition to a centralized origin of the pain.