Shear wave elastography for upper limb muscle stiffness assessment in patients with rigidity-dominant Parkinson's disease

Abstract Background Myotonia is the central clinical symptom of Parkinson's disease(PD), and myotonic conditions can be used to assess the severity of PD.Therefore, the aim of this study was to characterize the stiffness of limb muscles using ultrasound shear-wave elastography (SWE), and the validity of this method in assessing myotonia in PD. Methods From April 2019 to January 2020, SWE of the longitudinal biceps brachii and brachioradialis was performed on 60 PD patients and 30 healthy controls. The stiffness of the limb muscles, as measured by quantitative Young's modulus (YM), was compared between the remarkably symptomatic and mildly symptomatic sides of PD, as well as between PD patients and controls. The correlation between YM of the biceps brachii and brachioradialis with age, duration, and motion scores assessed by the unified PD Rating scale (UPDRS) part III was analyzed by Pearson's correlation coefficient. The reliability of SWE was tested using the intraclass correlation coefficient (ICC). Results (1) YM of the long axis of the biceps brachii and brachioradialis in PD patients were higher than in the control group (P<0.05), and were higher on the remarkably symptomatic side than on the mildly symptomatic side (P<0.05). The ICC for interobserver and intraobserver variations in measuring YM were 0.86 (95% confidence interval 0.54–0.96) and 0.93 (95% confidence interval 0.70–0.98), respectively, for biceps brachii and 0.84 (95% confidence interval 0.47–0.96) and 0.91(95% confidence interval 0.64–0.98), respectively, for brachioradialis. (2) A positive linear correlation was found between YM of longitudinal biceps brachii and brachioradialis on the remarkably symptomatic side in PD patients with the motion scores (r=0.462, P<0.001; r༝0.356, P0.05). Conclusions SWE can be used as a quantitative assessment of muscle stiffness in patients with PD.