Electrical impedance myography: Transitioning from human to animal studies

Objective: To determine the feasibility of performing electrical impedance myography (EIM) in rats. Methods: EIM was performed on the hamstring muscles of 6 healthy adult rats with applied frequencies of 2-300 kHz. Studies were performed over a 6-week period, with 3 rats having recordings made from the skin (surface EIM) and 3 with recordings directly from the muscle (direct-muscle EIM). In addition, sciatic nerve crush was performed on one rat and comparisons made pre- and post-injury. Reactance and resistance were measured and the primary outcome variable, the phase angle (0), calculated. Results: EIM patterns in the rat hamstring muscles were qualitatively similar to those observed in human subjects. This held true for both surface and direct-muscle recordings, although direct-muscle data appeared less repeatable. Sciatic nerve crush data in the single rat showed a dramatic reduction in phase and a relative loss of frequency-dependence. Conclusions: EIM data similar to that obtained from human subjects can be acquired from rat muscles with surface recordings proving more consistent and easier to obtain than direct-muscle recordings. Changes seen with sciatic nerve crush mirror those seen in patients with neurogenic injury. Significance: These results support the possibility of performing EIM on rat models of neuromuscular disease. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.