Wireless transmission of voltage transients from a chronically implanted neural stimulation device

Abstract

Objective. Consistent transmission of data from wireless neural devices is critical for monitoring the condition and performance of stimulation electrodes. To date, no wireless neural interface has demonstrated the ability to monitor the integrity of chronically implanted electrodes through wireless data transmission. Approach. In this work, we present a method for wirelessly recording the voltage transient (VT) response to constant-current, cathodic-first asymmetric pulsing from a microelectrode array. We implanted six wireless devices in rat sciatic nerve and wirelessly recorded voltage transient measurements throughout a 38-week implantation period. Main results. Electrode maximum cathodic potential excursion (Emc), access voltage, and driving voltage (extracted from each VT) remained stable throughout the 38-week study period. Average Emc(from an applied +0.6 V interpulse bias) in response to 4.7 µA, 200.2 µs pulses was 267 ± 107 mV at week 1 post-implantation and 282 ± 52 mV at week 38 post-implantation. Access voltage for the same 4.7 µA pulsing amplitude was 239 ± 65 mV at week 1 post-implantation and 268 ± 139 mV at week 38 post-implantation. Significance. The voltage transient response recorded via reverse telemetry from the wireless microelectrode array did not significantly change over a 38-week implantation period and was similar to previously reported VTs from wired microelectrodes with the same geometry. Additionally, the voltage transient response recorded wirelessly in phosphate buffered saline before and after device implantation appeared as expected, showing significantly less electrode polarization and smaller access voltage than the VT response in vivo.

A portable neurostimulator circuit with anodic bias enhances stimulation injection capacity

“…We developed a single printed circuit board-based neurostimulator system that simplified such issues while allowing for efficient stackup layer plan and crosstalk and coupling elimination. Application-specific IC-based neurostimulators can further miniaturize overall form-factors [35][36][37].…”

In‐vivo testing of a novel wireless intraspinal microstimulation interface for restoration of motor function following spinal cord injury

“…The ability to capture the electrode's voltage transients (VT) during constant‐current pulsing is of particular importance for ensuring that the electrode can deliver charge safely during stimulation without exceeding the potential limits associated with water electrolysis, electrode damage, or tissue damage. The VT data were wirelessly collected via the WFMA's reverse telemetry function for each of the 16 electrodes within each of the two WFMA devices, according to previously reported methods 14 . VT data were recorded at two time points; prior to device implantation, with the devices submerged in phosphate‐buffered saline (PBS: 0.126 M NaCl, 0.081 M Na 2 HPO 4 , 0.022 M NaH 2 PO 4 , pH 7.1–7.3), and for a second time, upon implantation in the spinal cord.…”

“…V acc is associated with the access resistance of the electrode. Previous studies have shown that V acc in vivo can be three to eight times larger than V access in PBS 14 . An example of a VT recorded from one of the electrodes is shown in Figure 5 and is labeled with each value of interest for assessing electrode performance.…”

“…The VT data were wirelessly collected via the WFMA's reverse telemetry function for each of the 16 electrodes within each of the two WFMA devices, according to previously reported methods. 14 VT data were recorded at two time points; prior to device implantation, with the devices submerged in phosphate-buffered saline (PBS: 0.126 M NaCl, 0.081 M Na 2 HPO 4 , 0.022 M NaH 2 PO 4 , pH 7.1-7.3), and for a second time, upon implantation in the spinal cord. In vitro VT data were collected in PBS at current levels of 20, 40, and 80 μA for both WFMA devices.…”