Effect of Bipolar Cuff Electrode Design on Block Thresholds in High-Frequency Electrical Neural Conduction Block

Abstract

Many medical conditions are characterized by undesired or pathological peripheral neurological activity. The local delivery of high-frequency alternating currents (HFAC) has been shown to be a fast acting and quickly reversible method of blocking neural conduction and may provide a treatment alternative for eliminating pathological neural activity in these conditions. This work represents the first formal study of electrode design for high-frequency nerve block, and demonstrates that the interpolar separation distance for a bipolar electrode influences the current amplitudes required to achieve conduction block in both computer simulations and mammalian whole nerve experiments. The minimal current required to achieve block is also dependent on the diameter of the fibers being blocked and the electrode–fiber distance. Single fiber simulations suggest that minimizing the block threshold can be achieved by maximizing both the bipolar activating function (by adjusting the bipolar electrode contact separation distance) and a synergistic addition of membrane sodium currents generated by each of the two bipolar electrode contacts. For a rat sciatic nerve, 1.0–2.0 mm represented the optimal interpolar distance for minimizing current delivery.

High-Frequency Stimulation Selectively Blocks Different Types of Fibers in Frog Sciatic Nerve

“…Prior simulation work has indicated that the frequency of the waveform, the computational model used, and the possible interactions between the nodes of Ranvier, are key issues in achieving the localized electrical nerve block and these factors could affect the block threshold at each frequency [5, 9, 10, 23, 24]. Yet in all these computational studies a linear relationship with frequency was found even for smaller diameter axons.…”

Design, fabrication and evaluation of a conforming circumpolar peripheral nerve cuff electrode for acute experimental use

“…The spacing between the contacts is defined as the inter-polar distance (IPD), where the ‘poles’ are the geometric centers of each electrode contact. The IPD was often chosen to be the most efficient configuration for stimulation (Holsheimer and Wesselink, 1997) or blocking (Ackermann et al, 2009) given the nerve diameter, expected fiber diameter distribution within the nerve, and the intended purpose of the electrical stimulation (i.e. activation or conduction block).…”

“…This electrode design has been successfully used in multiple whole nerve neurostimulation studies to date, and has been shown to produce robust and repeatable recruitment of nerve fibers during stimulation (Bhadra et al, 2006; Miles et al, 2007; Bruns et al, 2008; Ackermann et al, 2009; Lewandowski et al, 2009; Mariano et al, 2009; Ackermann et al, 2010; Ackermann et al, in press) and conduction block (Bhadra and Kilgore, 2005; Bhadra et al, 2006; Miles et al, 2007; Boger et al, 2008; Ackermann et al, 2009; Ackermann et al, in press). It has also been used for recording compound action potentials (Lahowetz et al, 2007).…”

Nerve conduction block using combined thermoelectric cooling and high frequency electrical stimulation

“…The distal electrode was used for the delivery of HFAC blocking currents to the nerve. The electrodes were bipolar with a 1.0 mm edge-to-edge contact spacing and 1.0 mm of silicone rubber between the edge of the outer platinum contact and each edge of the cuff (Ackermann et al, 2009). The HFAC waveforms were 40 kHz voltage-controlled sinusoids and were delivered using a Wavetek 395 waveform generator (now Willtek Communications GmbH, Ismaning, Germany).…”