T136. Assessing myofiber size without biopsy: A novel application of electrical impedance techniques

Abstract

Introduction In electrical impedance myography (EIM) a weak electrical current is applied to a muscle and the resulting voltages measured. These voltages can provide structural and compositional information on the tissue, including the presence of myofiber loss and the deposition of fat and connective tissue. In addition, based on standard bioimpedance theory, by applying a multifrequency current, structural characteristics of the fibers can be identified, including myofiber size. In this study, we assessed the potential of EIM to identify myofiber size non-invasively in both healthy and diseased muscle. Methods In electrical impedance myography (EIM) a weak electrical current is applied to a muscle and the resulting voltages measured. These voltages can provide structural and compositional information on the tissue, including the presence of myofiber loss and the deposition of fat and connective tissue. In addition, based on standard bioimpedance theory, by applying a multifrequency current, structural characteristics of the fibers can be identified, including myofiber size. In this study, we assessed the potential of EIM to identify myofiber size non-invasively in both healthy and diseased muscle. Results Using the LASSO approach, we successfully predicted myofiber size with high accuracy in the wild type immature (root mean standard error (RMSE) in the range of ±69.05 (16.2% with respect to the average myofiber size of 491 μ m 2 ). Similar accuracy was also achieved in the ALS animals with an RSME of only 14% in mean myofiber area (corresponding to ±207 μ m 2 for a mean area of 1488 μ m 2 ); in addition, in this group of animals we were also able to demonstrate that we could accurately predict the coefficient of variation in fiber size with a RMSE of only 8.8%. Conclusion These results demonstrate that impedance techniques can be used to assess myofiber size without the need for actual tissue biopsy. This approach for assessing the degree of myofiber size demands further development and potential application in a variety of future contexts including the assessment of neuromuscular disease status, disuse-related alterations, and the impact of therapy.