Electrode contact configuration and energy consumption in spinal cord stimulation

Objective: To test the hypothesis that in spinal cord stimulation, an increase in the number of cathodes increases the energy per pulse, contrary to an increase in the number of anodes, which decreases energy consumption per pulse.

Methods: Patients with an Itrel III (7425; Medtronic, Inc., Minneapolis, MN) implantable pulse generator and a Pisces-Quad (3487A; Medtronic, Inc.) implantable quadripolar lead were selected for this study. A set of 7 standard contact configurations was used for each patient. Resistor network models mimicking these configurations were constructed. The University of Twente’s Spinal Cord Stimulation software was used to simulate the effect of these contact configurations on large spinal nerve fibers. To allow a comparison of the measured and modeled energy per pulse, all values were normalized.

Results: Both the empirical and the modeling results showed an increase in energy consumption with an increasing number of cathodes. Although the patient data with 1 and 2 cathodes did not differ significantly, energy consumption was significantly higher when 3 cathodes were used instead of 1 or 2 cathodes. The average energy consumption was significantly higher when bipolar stimulation was used instead of monopolar cathodal stimulation. An increasing number of anodes caused a decrease in energy consumption.

Conclusion: When the paresthesia area can be covered with several configurations, it will be beneficial for the patient to program a configuration with 1 cathode and either no or multiple anodes.