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.
Highlights
Myotonia describes delayed muscle relaxation after activation
RT0.1, rSWVmean baseline phase and rSWVmean fist clenching phase were compared between groups
For the differentiation between groups according to RT0.1, a receiver operating characteristic (ROC) curve analysis was performed
Summary
Myotonia describes delayed muscle relaxation after activation. It is the eponymous symptom and clinical sign of myotonic muscle disorders, causing disability and reduction in quality of life [1,2]. Previous clinical studies used the following options: (1) patientreported outcomes, such as the Myotonia Behaviour Scale [7]; (2) clinical observation and timing of myotonia after closing eyes or clenching a fist, as well as the presence of percussion myotonia [3,5]; (3) quantitative measurement of the increased relaxation time of finger flexors with a dynamometer [8,9,10,11]; (4) functional tests of the lower extremities such as the Timed Up And Go or 14 Step Stair Test [6]; and (5) electrophysiological tests such as electromyographical relaxation time [3] or the maximal post-exercise decrement in compound muscle action potential after short and long exercise [5]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
