Optimizing measurement of the electrical anisotropy of muscle

Chin, Alexander F.; Garmirian, Lindsay P.; Nie, Rui; Rutkove, Seward B.

doi:10.1002/mus.20981

Cited by 38 publications

(44 citation statements)

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“…Frequency-dependence to the changes was observed in our one other study assessing anisotropy alterations in the tibialis anterior muscle of human subjects (Chin et al, 2008), although drawing comparisons between these two investigations is difficult since in that study only two ALS individuals were studied. Interestingly, in that study, the subject with very longstanding atrophy and weakness of the tibialis anterior (the one muscle studied) showed a flattening of the spectrum and reduction in anisotropy, whereas the one with only moderate weakness of the tibialis anterior muscle showed an elevation across the frequency spectrum, suggesting that the duration of neurogenic injury also affects the muscle’s anisotropy.…”

Section: Discussionmentioning

confidence: 84%

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Alteration in surface muscle electrical anisotropy in the rat SOD1 model of amyotrophic lateral sclerosis

Rutkove

2012

Clinical Neurophysiology

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Objective To evaluate the effects of progressive neurogenic change on surface-measured anisotropy via study in the rat superoxide dismutase 1 (SOD1) G93A amyotrophic lateral sclerosis (ALS) model. Methods Eight male ALS rats were studied over a period of 10 weeks. In each, the 20 kHz to 1 MHz electrical impedance of the gastrocnemius-soleus complex was measured with electrodes placed at 0° and at 90° relative to the major muscle fiber direction. The major outcome measure, the anisotropy difference (AD) for each of the resistance, reactance, and phase, was calculated as 90° – 0° values. Results All three parameters showed substantial alterations with disease progression. However, the phase AD demonstrated the most substantial change, increasing from 1.8 ± 1.58° to 10.2 ± 2.13° (mean ± standard error) comparing the first and last set of measurements (p = 0.028). Conclusions Anisotropy increases substantially with disease progression in the ALS rat. Significance Measurement of surface electrical anisotropy offers a non-invasive means for quantifying neurogenic change in muscle.

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Section: Discussionmentioning

confidence: 84%

“…There is also a strong frequency-dependence to this property. In fact, this characteristic of muscle was recognized nearly 50 years ago (Rush 1962; Fatt 1964), but its potential value for muscle disease assessment has only recently been appreciated (Garmirian et al, 2009; Chin et al, 2008). …”

Section: Introductionmentioning

confidence: 99%

Alteration in surface muscle electrical anisotropy in the rat SOD1 model of amyotrophic lateral sclerosis

Rutkove

2012

Clinical Neurophysiology

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“…perpendicular to them) (Aaron et al 1997; Tarulli et al 2006). We have also previously demonstrated that patients with a variety of neuromuscular diseases have a disrupted muscle anisotropy compared to healthy individuals (Chin et al 2008; Garmirian et al 2009). …”

Section: Introductionmentioning

confidence: 84%

Loss of electrical anisotropy is an unrecognized feature of dystrophic muscle that may serve as a convenient index of disease status

Rutkove

Zaidman

et al. 2016

Clinical Neurophysiology

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Objective We sought to understand the alteration in the anisotropic, or direction dependent, character of muscle as measured by electrical impedance myography (EIM) in subjects with Duchenne muscular dystrophy (DMD) and its potential to serve as a biomarker of disease status. Methods Thirty-six boys with DMD and 27 healthy controls were measured with EIM, with electrical current applied both parallel and perpendicular to the major muscle fiber direction. In addition, muscle extracted from10 mdx and 10 wild-type mice were measured analogously. Results Normalized reactance anisotropy, a direction-dependent measure of membrane charge storage capability, was significantly lower in the four muscles of DMD subjects as compared to controls (p < 0.01). Normalized reactance anisotropy also decreased with increasing age in DMD subjects (r = −0.36, p = 0.031), but not in healthy boys. Analogous changes were observed in mdx mouse gastrocnemius as compared to wild type (p = 0.019). Conclusion These results support that loss of electrical anisotropy is a previously unrecognized feature of dystrophic muscle. Significance Anisotropic alterations may offer novel indices to assist in neuromuscular disease diagnosis and to serve as easy-to-obtain biomarkers in clinical therapeutic trials.

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“…The anisotropy of the muscle can also be assessed by using this approach since the direction of applied current flow can be varied along with the voltage electrodes, by rotating the four-electrode set around a center point over the muscle of interest (Figure 4), and thus providing a detailed assessment of the impedance characteristics of the muscle in different directions 7. The one major disadvantage to this approach is the effect of the skin-fat layer the current must traverse.…”

Section: General Approaches To Performing Impedance Measurement On Mumentioning

confidence: 99%

Electrical impedance myography: Background, current state, and future directions

2009

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Electrical impedance myography (EIM) is a new non-invasive technique for the evaluation of neuromuscular disease that relies upon the application and measurement of high-frequency, lowintensity electrical current. EIM assesses disease-induced changes to muscle's normal composition and architecture, including myocyte atrophy and loss, edema, reinnervation, and the deposition of endomysial connective tissue and fat. With application of single-frequency electrical current, EIM can be used to help grade the severity of neuromuscular disease. Assessing electrical impedance across a spectrum of applied frequencies and with current flow at multiple orientations relative to the major muscle fiber direction can provide a more complete picture of muscle condition. EIM holds the promise of serving as an indicator of disease status, thus being useful in clinical trials work and in monitoring effectiveness of treatment in individual patients; ultimately, it may also find diagnostic application. Ongoing efforts have been focused on obtaining a deeper understanding of the basic mechanisms of impedance change, studying EIM in a variety of clinical contexts, and further refining the methods of EIM data acquisition and analysis. KeywordsElectrical impedance; muscle; neuromuscular disease; technique; anisotropy Electrical impedance myography (EIM) is a non-invasive, painless approach to muscle assessment based upon the application and measurement of high-frequency, low-intensity electrical current (Figure 1). In contrast to conventional needle electromyography (EMG) and most standard neurophysiological techniques, EIM does not focus on measuring the inherent electrical activity of the tissues. Rather, similar to diagnostic ultrasound, measurements are made over a small area of interest, with energy being applied to the body and the resultant surface patterns analyzed. Unlike ultrasound, however, in which energy is in the form of sound waves and the main interest is image reconstruction, in the case of EIM, electrical current is used and the output is a set of quantitative parameters describing the state of the muscle, with presently little emphasis on imaging (though this remains possible). Although still in a relatively early stage of development, EIM may have important clinical uses in the future, both as an indicator of neuromuscular disease status and as a diagnostic tool. This review will begin with a brief history of bioelectricity in neuromuscular disease, exploring why electrical impedance measurements have been essentially overlooked as a potential means of muscle assessment. It will then detail the basic concepts underlying impedance measurements in general and the substantial challenges of applying them effectively to muscle.Please address correspondence to: Seward B. Rutkove, MD, Beth Israel Deaconess Medical Center, Department of Neurology, 330 Brookline Avenue, Shapiro 810, Boston, MA 02215; srutkove@bidmc.harvard.edu, Tel: 617-667-8130; Fax: 617-667-8747. NIH Public Access It will then review the data tha...

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Optimizing measurement of the electrical anisotropy of muscle

Cited by 38 publications

References 12 publications

Alteration in surface muscle electrical anisotropy in the rat SOD1 model of amyotrophic lateral sclerosis

Alteration in surface muscle electrical anisotropy in the rat SOD1 model of amyotrophic lateral sclerosis

Loss of electrical anisotropy is an unrecognized feature of dystrophic muscle that may serve as a convenient index of disease status

Electrical impedance myography: Background, current state, and future directions

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