Electrical Impedance Myography and Its Applications in Neuromuscular Disorders

Abstract

Electrical impedance myography (EIM) refers to the specific application of electrical bioimpedance techniques for the assessment of neuromuscular disorders. In EIM, a weak, high-frequency electrical current is applied to a muscle or muscle group of interest and the resulting voltages measured. Among its advantages, the technique can be used noninvasively across a variety of disorders and requires limited subject cooperation and evaluator training to obtain accurate and repeatable data. Studies in both animals and human subjects support its potential utility as a primary diagnostic tool, as well as a biomarker for clinical trial or individual patient use. This review begins by providing an overview of the current state and technological advances in electrical impedance myography and its specific application to the study of muscle. We then provide a summary of the clinical and preclinical applications of EIM for neuromuscular conditions, and conclude with an evaluation of ongoing research efforts and future developments.

Predicting myofiber size with electrical impedance myography: A study in immature mice

“…In addition, we obtained the RMSE of 72.12 µm 2 in a model containing only phase, implying that all 3 components, resistance, reactance and phase, included in a single model improve prediction. A final limitation of the analysis performed is that it does not include any measurement of anisotropy . Anisotropy, or the directional dependence of electrical current flow in muscle, plays a substantial role in muscle because of the cylindrical shape of muscle fibers.…”

“…A final limitation of the analysis performed is that it does not include any measurement of anisotropy. 1 Anisotropy, or the directional dependence of electrical current flow in muscle, plays a substantial role in muscle because of the cylindrical shape of muscle fibers. However, because of the very small size of each of these animals, it would have been challenging in the extreme to obtain 2-directional data with any accuracy.…”

“…Muscle Nerve 58: [106][107][108][109][110][111][112][113]2018 Electrical impedance myography (EIM) is a neurophysiological technique in which a low-intensity, high-frequency current is passed through tissue, and the resulting voltages are measured. 1 From these values, the impedance of the tissue can be identified, including the major parameters of resistance, reactance, and phase angle. Changes in the impedance characteristics of tissue are altered in disease states.…”

Sensitivity distribution simulations of surface electrode configurations for electrical impedance myography

“…Electrical impedance myography (EIM) is an impedance‐based technique for the assessment of neuromuscular disorders (NMDs) . In its standard application, a set of 4 surface electrodes is placed on the skin over a muscle or muscle group of interest and the voltage resulting from the application of a high‐frequency and low‐amplitude electric current is measured.…”

“…Whereas the term “myography” in EIM's name implies that the technique assesses muscle condition alone, in fact, EIM's resistance and reactance values have contributions from all tissues underlying the electrodes. In the frequency range where EIM is typically measured (kilohertz to megahertz), NMD alters the inherent dielectric properties of resistivity and relative permittivity of the muscle itself, which produces changes in the resistance and reactance values . Moreover, EIM changes observed in progressive diseases likely reflect alterations in the size and shape of the muscle in relation to its surrounding tissues.…”