Contact configuration and energy consumption in spinal cord stimulation

Objective: To test the hypothesis that, in contrast to an increase of the number of anodes which reduces energy consumption per pulse, an increase of the number of cathodes raises the energy consumption. Materials and Methods: Patients with an Itrel 3 Pulse Generator and a Pisces Quad quadripolar lead have been selected for this study. A set of 7 standard contact configurations was used in each patient. Resistor network models mimicking these configurations were made. The UT-SCS volume conductor modeling software has been used to simulate the effect of these contact configurations on spinal nerve fibers. To allow a comparison of the measured and modeled energy/pulse, all values were normalized. Results: Both the empirical and the modeling results showed an increase of 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 cathode 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 of 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 none or multiple anodes.