Two non-invasive strategies for measuring muscle function and its properties, electromechanical delay and ultrasound shear wave elastography, may help detect muscle impairments and assist in monitoring Duchenne muscular dystrophy (DMD) patients’ responses to therapy.
The study “Effects of Duchenne muscular dystrophy on muscle stiffness and response to electrically-induced muscle contraction: A 12-month follow-up,” was published in the journal Neuromuscular Disorders.
As new therapies are under development for children with DMD, it is equally important to develop non-invasive and sensitive methods to assess muscle function and properties. Currently, two approaches show great potential: The first, electromechanical delay (EMD), detects the time lag between muscle activation and force production; a second approach, ultrasound shear wave elastography, assesses the ability of muscle stiffness using a newer type of ultrasound.
“The assessment of both muscle stiffness and responses to electrically-induced contractions (EMD and torque amplitude) can provide important information related to muscle function and structure with potential relevance to clinical and therapeutic assessments,” researchers wrote.
In the study, researchers assessed the ability of both methods to detect alterations in the properties of muscles from children with DMD.
“We hypothesized that both muscle stiffness and the electromechanical delay would be increased after a 12-month period in patients with DMD,” researchers explained.
To this end, they recruited 10 DMD children and nine age-matched healthy males in a control group. Both DMD patients and the control subjects participated in two experimental sessions, at time zero and after 12 months, where they were submitted to electrically induced contractions and measurements of muscle stiffness.
Researchers found that both non-invasive strategies were capable of detecting changes in muscle function and properties in children with DMD. Moreover, they highlighted that “the present data showed a progressive lengthening of the time required for the muscle force to be transmitted to the skeleton in patients with DMD.”
These results suggest, the authors wrote, “that during childhood, growth and maturation may partly compensate for strength decrease but not for force transmission deterioration, which in turn is more inherent to the disease process.”
In DMD patients, they also detected increased localized muscle stiffness in certain muscles.
Overall, both non-invasive methods proved efficacious in measuring muscle stiffness, force transmission and force production in patients with DMD. This is particularly important in the assessment of DMD patients’ responses to therapeutics.