Quantifying Myofascial Dysfunction in Post-Stroke Pain

Shoulder pain is extremely common after stroke and occurs in 30-70% of patients. Chronic post stroke shoulder pain (PSSP) contributes to depression, interferes with motor recovery, and decreases quality of life. Although PSSP is thought to be caused by damage to the myofascial tissues around the shoulder joint, the pathophysiology of myofascial dysfunction and pain in PSSP has not been elucidated, leading to missed opportunities for early diagnosis, and variable success with pain management. The accumulation of HA in muscle and its fascia can cause myofascial dysfunction. HA is a GAG and a chief constituent of the extracellular matrix of muscle. In physiologic quantities, it functions as a lubricant and a viscoelastic shock absorber, enabling force transmission during muscle contraction and stretch. Reduced joint mobility and spasticity can result in focal accumulation and alteration of HA in muscle, leading to the development of taut bands, dysfunctional gliding of deep fascia and muscle layers, Reduced Range of Motion (ROM), and pain. Muscle HA concentrations can be imaged using T1ρ MRI, and myofascial dysfunction can be assessed using echo texture analysis and shear strain mapping on quantitative US, which may serve as useful biomarkers to elucidate the pathophysiology of myofascial dysfunction in PSSP.