Myofascial pain syndrome can cause not only the pain, but also the muscle stiffness by the densification of excessive hyaluronic acid in muscle and fascia. The first aim of this study was to evaluate the therapeutic effects of microcurrent electrical neuromuscular stimulation on chronic myofascial pain syndrome of upper trapezius muscles and the second aim was to evaluate the viscoelastic change of myofascial trigger points and neighboring tissues with ultrasonoelastography using acoustic radiation force impulse (ARFI) imaging.

This study was designed as a prospective, randomized, double-blinded, placebo-controlled trial. The patients with chronic neck pain who visited the outpatient clinic voluntarily were included in this study. Total 40 minutes’ microcurrent electrical therapy using a Granthe Advance (8Hz, 25μA, Cosmic Co., Seoul, Korea) or sham stimulation was applied on both upper trapezius muscles daily for 2 weeks, total 14 times. All MENS and control groups took the standard care including postural education, and self-exercise. All participants visited total 3 times; baseline, 2 weeks and 4 weeks follow-up. At every visit, we evaluated the usage of analgesics, existence of trigger points of upper trapezius, Visual Analogue Scale (VAS), pressure pain threshold, neck range of motion (ROM), and viscoelasticity by shear wave velocity using ultrasonoelastography.

There was no significant difference in baseline characteristics. MENS significantly improved pressure pain threshold on upper trapezius muscles (P=0.001). Also, MENS significantly reduced shear wave velocity (P=0.001) on upper trapezius muscles and patients rated pain intensity (P=0.024). The detailed values were summarized in Table 1.

Our findings demonstrate that the microcurrent electrical neuromuscular stimulation improved pressure pain threshold, pain intensity and shear wave velocity in chronic myofascial pain syndrome on upper trapezius muscles. Therefore, MENS can be a useful treatment tool for the myofascial pain syndrome.