source: American Academy of Neurology
Seward Rutkove, Kush Kapur, Jim Wu, Craig Zaidman, Amy Pasternak, Lavanya Madabusi, Heather Szelag, Tim Harrington, Adam Pacheck, Sung Yim, Basil Darras
To evaluate the capability of electrical impedance myography (EIM) to detect disease progression in boys with Duchenne muscular dystrophy (DMD).
Easily applied tools to serve as biomarkers for clinical trials in DMD to evaluate disease progression and response to therapy are needed. EIM has been shown to be sensitive to disease progression in other conditions and to be highly repeatable and to correlate to functional assessments in DMD. Here we evaluate its ability to detect disease progression in DMD boys by comparing their data to those of healthy controls.
Thirty boys with DMD (7.4±3.6 years) and 29 healthy boys (7.1±3.1 years) underwent intermittent multifrequency EIM on 6 muscles unilaterally (deltoid, biceps, forearm flexors, quadriceps, tibialis anterior, and medial gastrocnemius) over 2 years. Analysis was performed using a linear mixed-effects model for each muscle’s EIM data with random intercept and slope terms to account for within-subject correlations and between-subject variability.
Significant differences in slopes between healthy and DMD boys were evident. In the older boys, these differences were more significant in upper extremity muscles, whereas as in younger, they were more marked in the lower extremities. For example, at 24 months, in boys 7 years and older, the reactance ratio of biceps showed a slope of -0.00771 compared to healthy controls (p<0.0001). In the children under 7 years, the 100 kHz transverse phase in gastrocnemius showed a slope of +0.2264 (p=0.0012) at 24 months. In both cases, significant differences were already present at 1 year.
EIM parameters sensitively detect disease progression in muscle in boys with DMD. The nature of these temporal alterations appears-age dependent and will require further analysis so as to most effectively apply them in a clinical therapeutic trial setting.