Functional monitoring of peripheral nerves from electrical impedance measurements

In this study, we investigate the feasibility of using electrical impedance (EI) measurements as an in vivo functional nerve monitoring technique. The monitoring paradigm includes the synchronized recording of both the evoked endogenous activity as compound action potentials (CAP) and the superimposed sine signal from the EI probe. Measurements were conducted on the sciatic nerve of rodents, chosen for its branchings towards the peroneal and tibial nerves, with both mono- and multi-contact per section electrodes. During stimulation phases, recordings showed CAP with consistent fiber conduction velocities. During coupled phases of both stimulation and sine perturbation, impedance variations were extracted using the mono-contact electrode type for certain frequencies, e.g. 2.941kHz, and were temporally coherent with the previous recorded CAP. Using a MCC, localized evoked CAP were also recorded but the signal to noise ratio (SNR) was too low to distinguish the expected associated impedance variation and deduce an image of impedance spatial changes within the nerve. The conducted in vivo measurements allowed to distinguish both evoked CAP and associated impedance variations with a strong temporal correlation. This indicates the feasibility of functional EI monitoring, aiming at detecting the impedance variations in relation to neural activity. Further work is needed to improve the in vivo system, namely in terms of SNR, and to integrate new multicontact devices in order to move ...

Source: Journal of Physiology Paris - June 3, 2017 Category: Physiology Source Type: research