Muscle Ultrasound Shear Wave Elastography as a Non-Invasive Biomarker in Myotonia

Abstract

Myotonia, i.e., delayed muscle relaxation in certain hereditary muscle disorders, can be assessed quantitatively using different techniques ranging from force measurements to electrodiagnostics. Ultrasound shear wave elastography (SWE) has been proposed as a novel tool in biomechanics and neuromuscular medicine for the non-invasive estimation of muscle elasticity and, indirectly, muscle force. The aim of this study is to provide ‘proof-of-principle’ that SWE allows a quantitative measurement of the duration of delayed muscle relaxation in myotonia in a simple clinical setting. In six myotonic muscle disorder patients and six healthy volunteers, shear wave velocities (SWV) parallel to the fiber orientation in the flexor digitorum superficialis muscle in the forearm were recorded with a temporal resolution of one per second during fist-clenching and subsequent relaxation; the relaxation time to 10% of normalized shear wave velocity (RT0.1) was calculated. Forty-six SWE imaging sequences were acquired, yielding a mean RT0.1 of 7.38 s in myotonic muscle disorder patients, significantly higher than in healthy volunteers (1.36 s), which is comparable to data obtained by mechanical dynamometry. SWV measurements during the baseline relaxation and voluntary contraction phases did not differ significantly between groups. We conclude that SWE is a promising, non-invasive, widely available tool for the quantitative assessment of myotonia to aid in diagnosis and therapeutic monitoring.

Analysis of the thenar muscles with ultrasound shear wave elastography: Reliability and preliminary findings

“…This conversion relies on the assumption that the medium is purely elastic without viscous components and perfect isotropy. 29 Muscle tissue is, however, not purely elastic and is not isotropic 17 and therefore, the conversion assumptions are violated.…”

Characterization of Muscle Weakness Due to Myasthenia Gravis Using Shear Wave Elastography

“…Despite such challenges in relating the measured shear wave speed to muscle stiffness, previous studies denoted the promising clinical use of SWE in muscle diagnostics and therapeutic monitoring, e.g., for patients with myositis, stroke, cerebral palsy or multiple sclerosis [ 18 ]. SWE was claimed to be a biomarker in myotonia as the muscle relaxing time estimated using SWE was similar to those obtained with mechanical dynamometers [ 19 ]. Increased shear wave speed under passive conditions of the biceps brachii muscle (BB) was found in patients with Parkinson’s Disease [ 20 ] and it was shown that SWE output correlates with joint rigidity [ 21 ].…”

Ultrasound of the Biceps Muscle in Idiopathic Parkinson’s Disease with Deep Brain Stimulation: Rigidity Can Be Quantified by Shear Wave Elastography

“…Some reported increased SWV with age [29,30], while some reported a decreased value [24,31,32]. More recent studies [5,20] have led to the assumption that the differences regarding age and sex could remain negligible within the respective SD, though those clinical characteristics should be taken more into account in an extended, larger study. (3) We only correlated the SWV with clinical assessments according to the MDS-UPDRS.…”

“…For comparison, 10 healthy control subjects (HC) were examined. Matching by age and sex was omitted as in comparable SWE studies [20], among other reasons because the primary aim of this study was to show a longitudinal effect within PD, not to compare the results of PD patients to those of HC. All participants were over the age of 18 and provided informed consent.…”