Enhanced transcutaneous electrical nerve stimulation achieved by a localized virtual bipole: a computational study of human tibial nerve stimulation

摘要

Objective. Electrical neuromodulation is a clinically effective therapeutic instrument, currentlyexpanding into newer indications and larger patient populations. Neuromodulation technologiesare also moving towards less invasive approaches to nerve stimulation. In this study, weinvestigated an enhanced transcutaneous electrical nerve stimulation (eTENS) system thatelectrically couples a conductive nerve cuff with a conventional TENS electrode. The objectiveswere to better understand how eTENS achieves lower nerve activation thresholds, and to test thefeasibility of applying eTENS in a human model of peripheral nerve stimulation. Approach. A finiteelement model (FEM) of the human lower leg was constructed to simulate electrical stimulation ofthe tibial nerve, comparing TENS and eTENS. Key variables included surface electrode diameter,nerve cuff properties (conductivity, length, thickness), and cuff location. Enhanced neuralexcitability was predicted by relative excitability (RE > 1), derived using either the activatingfunction (AF) or the nerve activation threshold (MRG model). Main results. Simulations revealedthat a localized ‘virtual bipole’ was created on the target nerve, where the isopotential surface of thecuff resulted in large potential differences with the surrounding tissue. The cathodic part (nervedepolarization) of the bipole enhanced neural excitability, predicted by RE values of up to 2.2(MRG) and 5.5 (AF) when compared to TENS. The MRG model confirmed that action potentialswere initiated at the cathodic edge of the nerve cuff. Factors contributing to eTENS were largersurface electrodes, longer cuffs, cuff conductivity (>1×10~3 S m~(−1)), and cuff position relative to thecathodic surface electrode. Significance. This study provides a theoretical basis for designing andtesting eTENS applied to various neural targets and data suggesting function of eTENS in largemodels of nerve stimulation. Although eTENS carries key advantages over existing technologies,further work is needed to translate this approach into effective clinical applications.