Is early diagnosis of myofascial pain syndrome possible with the detection of latent trigger points by shear wave elastography?

Myofascial pain syndrome (MPS) is a painful condition characterized by trigger points in taut muscle bands, with the upper trapezius being the most commonly affected in the cervical-scapular region. This study investigated whether shear wave elastography (SWE) can detect latent trigger points, which are clinically silent but may become active and cause symptoms later. The research enrolled 60 young women (mean age 20.6 years), divided into two groups: 30 with latent trigger points in the upper trapezius and 30 healthy controls. The diagnosis was based on the Travell and Simons criteria, which include five major criteria (spontaneous localized pain, altered sensations in the referred area, palpable taut band, localized tenderness, and reduced range of motion) and at least one minor criterion.

The myofascial syndrome group performed a self-stretching exercise program for 4 weeks, executing the movements 3 times per day with 10 repetitions each. The control group received no intervention. Elastography was performed by two experienced radiologists (13 and 14 years of experience) blinded to patient diagnosis, using a 9-12 MHz linear transducer. Measurements were standardized at the midpoint between the C7 spinous process and the acromion, with volunteers seated in a relaxed position.

Results showed significant differences in initial muscle stiffness between the groups. The myofascial syndrome group had mean stiffness of 60.3 ± 15.8 kPa, whereas the control group had 41.7 ± 9.6 kPa (p < 0.001). After 4 weeks of treatment, there was a significant reduction in muscle stiffness in the myofascial group (44.2 ± 12.0 kPa), with a mean difference of 16.1 kPa, while the control group remained unchanged. Inter-observer agreement was high (r = 0.97 initial, r = 0.93 final), confirming the reliability of the method.

The study also assessed pain via the Visual Analog Scale (VAS), finding moderate correlation (r = 0.595) between pain reduction and decreased muscle stiffness. The clinical implications are significant, since elastography offers an objective and quantitative tool for early diagnosis of myofascial syndrome, enabling intervention before clinical symptoms develop. The method also proved useful for monitoring treatment response. The pathophysiology of myofascial syndrome involves a vicious cycle in which increased acetylcholine at the motor end plate leads to permanent depolarization of the muscle fiber membrane, resulting in excessive contractions.

This causes hypoperfusion and ischemia, increasing inflammatory mediators and acidification, sensitizing nociceptors and perpetuating pain. Treatment with stretching exercises aims to break this cycle and is considered the therapeutic foundation of the condition. The study has important limitations, including the homogeneous young population, which may not represent all age groups affected by myofascial syndrome. In addition, it did not compare active and latent trigger points, focusing specifically on clinically silent cases.

The choice to use only stretching exercises as the intervention was motivated by ethical considerations, since the volunteers had no active symptoms.