Electrical impedance myography in individuals with collagen 6 and laminin α‐2 congenital muscular dystrophy: a cross‐sectional and 2‐year analysis

Abstract

Introduction: Electrical impedance myography (EIM) is a noninvasive electrophysiological technique that characterizes muscle properties through bioimpedance. We compared EIM measurements to function, strength, and disease severity in a population with congenital muscular dystrophy (CMD). Methods: Forty-one patients with CMD, either collagen 6 related disorders (COL6-RD; n 5 21) or laminin a-2-related disorders (LAMA2-RD; n 5 20), and 21 healthy pediatric controls underwent 2 yearly EIM exams. In the CMD cohorts, EIM was compared with functional and strength measurements. Results: Both CMD cohorts exhibited change over time and had correlation with disease severity. The 50-kHZ phase correlated well with function and strength in the COL6-RD cohort but not in the LAMA2-RD cohort. Discussion: EIM is a potentially useful measure in clinical studies with CMD because of its sensitivity to change over a 1-year period and correlation with disease severity. For COL6-RD, there were also functional and strength correlations.

Magnetic resonance imaging correlates with electrical impedance myography in facioscapulohumeral muscular dystrophy

“…In FSHD we showed test–retest reliability of EIM variables and broad correlations with FSHD disease measures . Despite its increasing use in muscular dystrophies, what EIM is measuring in the muscle is not well understood. Magnetic resonance imaging quantitative intramuscular Dixon fat fraction (FF) and a T1‐based muscle severity score (T1 muscle score) are promising biomarker candidates for alterations in FSHD muscle structure.…”

“…In congenital muscular dystrophy, EIM 50 kH Z phase was useful in tracking function and strength in ambulatory collagen VI patients but had no correlation with strength or function in the nonambulatory LAMA2 cohort . In Duchenne muscular dystrophy (DMD), EIM phase ratio showed a slope of decline steeper than traditional functional measures, likely reflecting the disease progression in muscles .…”

Electrical impedance myography in facioscapulohumeral muscular dystrophy: A 1‐year follow‐up study

“…It is still unclear which EIM variables are best suited to measure changes, and the choice for a specific variable depends on the disease being studied. Consequently, multiple studies have used different outcomes including, among others, single and multifrequency measures, single muscle and composite measures, single phase values, and phase ratios . Prior studies have shown that reactance is least susceptible to variability in subcutaneous fat content or electrode configuration .…”

“…Consequently, multiple studies have used different outcomes including, among others, single and multifrequency measures, single muscle and composite measures, single phase values, and phase ratios. 11,[13][14][15]25 Prior studies have shown that reactance is least susceptible to variability in subcutaneous fat content or electrode configuration. 26 Despite this, several studies have used phase ratios rather than reactance; this value appears to be optimized for function versus subcutaneous fat in muscle disease and, as a derived measure, uses both elements of reactance and resistance.…”

“…8,9 In a previous cross-sectional study on EIM in FSHD, we showed that EIM is a reliable measure of muscle composition in FSHD that correlates with functional outcome measures. 10 Studies on other neuromuscular disorders such as amyotrophic lateral sclerosis, congenital myopathies, and Duchenne muscular dystrophy have shown that EIM is able to capture changes over time, [11][12][13][14] although research is ongoing regarding what variables are most suitable to use in each different disorder.…”