Multimodal Imaging Biomarkers for Investigating Fascia, Muscle and Vasculature in Myofascial Pain

Definition of proposed composite multimodal biomarker-The investigators propose to develop a quantitative tissue-level classifier based on quantitative metrics (features) derived from ultrasound elastography, Doppler, bioimpedance spectroscopy and high-density electromyography, as an indicator of the normal biological process in myofascial tissues, and pathogenic process in active and latent phases of myofascial pain.

Overall approach and scientific rigor: In Aim 1, the investigators will develop methods to generate reproducible metrics (features) from the raw tissue-level measures and determine the minimum detectable change in these features in a pilot study. In Aim 2, the investigators will conduct a longitudinal observational study with two groups of subjects (control and myofascial pain). The investigators will develop a classification algorithm that optimally differentiates between active and latent phase of myofascial pain and normal myofascial tissue.

Study population and anatomical site. The chosen pain condition is chronic neck and shoulder pain. The investigators will recruit two groups of subjects: Group 1: Chronic myofascial pain as determined by baseline clinical examination using Travell and Simon's criteria7 and Group 2: pain free controls. The investigators will focus on two standardized anatomical locations (Figure 4). This will enable imaging the medial upper trapezius and the infraspinatus muscles, which are common locations for MTrPs55 as well as the levator scapulae. These three muscles have quite different morphology and fasciae45. The levator is a fusiform muscle with well-defined fascia that includes the muscle while the trapezius has thinner fascia from where perimysium septae cross the muscle belly. The infraspinatus has multiple fascial layers on its surface and has clear segmental linkages to the C5-6 segment56 Eligibility criteria: The investigators will recruit adults 18-65 years of age. Exclusion criteria: (1) diagnosis of fibromyalgia, chronic fatigue syndrome or chronic Lyme disease; (2) Diagnosis of cervical radiculopathy, neuropathy, or neuritis; (3) History of head, neck, cervical spine, or shoulder girdle surgery; (4) Atypical facial neuralgia; (5) New medication or change in medication in past 6 weeks; (6) Current throat or ear infection.

Masking and Matching: This is a single-blind longitudinal observational study. The team performing the data collection and analysis will not know the group allocation of the subjects and will be blinded to the results of the clinical evaluations. The two groups will be age and gender matched using a paired recruitment strategy57. The investigators will identify a pool of eligible control subjects with no history of pain and divide them into gender and age brackets (18-30; 31-50; and >50). For each Group 1 subject recruited in a bracket, the investigators will recruit a matched Group 2 subject from the pool.

Sex as a biological variable: Myofascial pain is widely prevalent in the community and affects both men and women. Trapezius myalgia is more prevalent in women58. The investigators will utilize age and gender-matched groups, and will test the classifier performance for both the pooled population as well as separately by gender to identify any gender-specific differences in the biomarker measures.