Evaluation of myotonometry for myotonia, muscle stiffness and elasticity in neuromuscular disorders

Abstract

Neuromuscular disorders show extremely varied expressions of different symptoms and the involvement of muscles. Non-invasively, myotonia and muscle stiffness are challenging to measure objectively. Our study aims to test myotonia, elasticity, and stiffness in various neuromuscular diseases and to provide reference values for different neuromuscular disease groups using a novel handheld non-invasive myometer device MyotonPRO®. We conducted a monocentric blinded cross-sectional study in patients with a set of distinct neuromuscular diseases (NCT04411732, date of registration June 2, 2020). Fifty-two patients in five groups and 21 healthy subjects were enrolled. We evaluated motor function (6-min walk test, handheld dynamometry, Medical Research Council (MRC) Scale) and used ultrasound imaging to assess muscle tissue (Heckmatt scale). We measured muscle stiffness, frequency, decrement, creep, or relaxation using myotonometry with the device MyotonPRO®. Statistically, all values were calculated using the t test and Mann–Whitney U test. No differences were found in comparing the results of myotonometry between healthy and diseased probands. Furthermore, we did not find significant results in all five disease groups regarding myotonometry correlating with muscle strength or ultrasound imaging results. In summary, the myometer MyotonPRO® could not identify significant differences between healthy individuals and neuromuscular patients in our patient collective. Additionally, this device could not distinguish between the five different groups of disorders displaying increased stiffness or decreased muscle tone due to muscle atrophy. In contrast, classic standard muscle tests could clearly decipher healthy controls and neuromuscular patients.

Novel Assessment of Viscoelastic Skeletal Muscle Properties in Chronic Kidney Disease: Association with Physical Functioning

“…In support of our results, previous research has shown relatively poor correlations between viscoelastic variables and objective muscle properties (muscle thickness and isometric strength) in chronic stroke patients with limited hypertonia [31]. Similar findings have also been reported elsewhere [32,33], including in adults with knee osteoarthritis where muscle stiffness of the rectus femoris was not associated with disability [18] and in those with neuromuscular disorders [34]. The concurrent measurement of muscle properties in relaxation and under contraction with a myotonometer and electromyography or dynamometer is suggested for future studies.…”