Single and modeled multifrequency electrical impedance myography parameters and their relationship to force production in the ALS SOD1G93A mouse

Abstract

Objective The relationship between muscle force production in ALS SOD1G93A mice and single and modeled multifrequency electrical impedance myography (EIM) parameters is unknown. We evaluated the relationship between multifrequency EIM data and paw grip and in situ force measurements, as well to standard measures in including body weight and compound motor action potential (CMAP) amplitude. Methods Twenty-nine SOD1 G93A mice aged 13-18 weeks (approximately 4-5 per week) and a group of similarly aged wild-type mice (N=7) were studied with single and multifrequency EIM, CMAP, front and hind-limb paw grip measures, and in situ force measurements of the gastrocnemius. Results Significant differences among WT, presymptomatic, and symptomatic ALS animals were identified for all standard measures and single 50 kHz frequency EIM parameters. Of the modeled multifrequency measures, the center frequency, fc, an index of cell size, showed the strongest relationship to force output. The two other multifrequency parameters corresponding to cell size distribution and cell density showed consistent although mostly non-significant differences. Conclusion Reductions in force are reflected in single 50 kHz impedance values and in the fc. These data support the construct validity of EIM as an assessment tool of muscle dysfunction in diseases associated with motor neuron loss.

Estimating Myofiber Size With Electrical Impedance Myography: a Study In Amyotrophic Lateral Sclerosis MICE

“…Those studies identified a strong relationship between EIM and these parameters. In addition, we have evaluated the relationship between EIM and force output in ALS mice and again found a robust relationship . It is perhaps not unexpected, therefore, that we identified a similar relationship between EIM and muscle fiber size here.…”

Non-invasive evaluation of muscle disease in the canine model of Duchenne muscular dystrophy by electrical impedance myography

“…Recent studies suggest that multi-frequency EIM is a better option in diagnosing normal from diseased muscle and even in distinguishing different neuromuscular diseases [26, 32, 37, 55]. By profiling three impedance parameters (resistance, reactance and phase), we obtained distinctive patterns between normal and affected dogs, suggesting EIM is a sensitive measure in the canine model of DMD (Fig 3).…”

“…Since sex may influence EIM [57], we need to expand our study to include both male and female normal dogs; (3) for the convenience, we have only studied one dog muscle (biceps femoris) in the current study. With the further development of the technique (for example, the custom-designed EIM apparatus), we may evaluate a variety of different surface muscles to gain a more global evaluation of the disease in the dog model; (4) in this study, we have focused on correlating the pathological findings with the EIM data, there is a need to determine whether the EIM data relate well with the results of physiological assays such as muscle force measurement, gait analysis and activity monitoring in dogs [12, 17, 18]; results in mdx mice (Seward B. Rutkove, unpublished results) and ALS mice suggest a relationship between muscle force measurement and impedance values [26]. Similarly, it will be worthwhile to compare EIM with muscle ultrasound and MRI [38, 40]; (5) as a cross-sectional study, we only selected two age groups.…”

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

“…Multifrequency resistance and reactance data were reduced to a set of 4 standard modeled parameters (the Cole parameters) by using the standard impedance model described elsewhere. 6,11,12 The first parameter is R 0 , which would be the highest resistance value were it possible to measure at 0 Hz frequency. The second parameter is R inf , which would be lowest resistance value were it possible to measure at infinite frequency.…”