Needle Impedance-Electromyography (I-EMG): a New Technique for the Electrodiagnostic Laboratory (P2.454)

Objective: We created a novel impedance-electromyography (I-EMG) needle electrode that expands needle electromyography (EMG) diagnostic capabilities by simultaneously measuring electrical impedance (I). Background: Needle EMG remains the standard clinical test for neuromuscular disease assessment, but it only characterizes myofiber membrane depolarization. On the other hand, impedance allows for quantitative measurement of muscle structure and composition, which could otherwise only be interrogated with muscle biopsy. To date, needle EMG and impedance could not be measured simultaneously with the same device. Design/Methods: We designed the first-of-its-kind needle electrode integrating impedance and EMG measurement capabilities. I-EMG recording characteristics were optimized via finite element method simulations. We compared measurements taken with our I-EMG needle and conventional EMG needle in muscle at rest and during activity in wild-type (wt, n =5) and muscular dystrophy ( mdx , n =5) mice at 6 weeks of age. Comparisons were assessed with Mann-Whitney test, two-tailed, p Results: The spontaneous EMG signal recorded using our I-EMG needle is similar to that obtained with a standard commercial monopolar EMG needle. Mdx muscle had lower impedance values as compared to wt muscle (p mdx mice. In addition, for the first time, our device demonstrates that impedance decreases simultaneously with EMG activation, likely due to increased myofiber membrane ion permeability during muscle activation. Conclusions: Needle I-EMG is a feasible and valuable improvement over conventional needle EMG, as it can provide muscle compositional and structural information that needle EMG cannot. Needle I-EMG could serve as a new bedside tool to assess neuromuscular disease without increasing the complexity or duration of the standard needle EMG. Disclosure: Dr. Rutkove has nothing to disclose. Dr. Kwon has nothing to disclose. Dr. Sanchez has nothing to disclose.