Patient-perceived differences between constant current and constant voltage spinal cord stimulation systems.

INTRODUCTION: Spinal cord stimulation (SCS) systems employ implantable pulse generators that use either a constant current (CC) or a constant voltage (CV) power source. CC power sources adjust voltage in response to resistance (impedance) to ensure that consistent current is delivered to the patient. CV power sources do not adjust voltage in response to impedance; therefore, current delivered to the patient will vary in response to changes in impedance. Both systems produce paresthesia and have been shown to treat chronic pain; however, it has been suggested that patients prefer CC stimulation over CV stimulation. MATERIALS AND METHODS: This Institutional Review Board-approved, randomized, double-blinded crossover study compared patient preference for the stimulation sensation elicited by a CC or CV neurostimulation system. Thirty patients completed a baseline evaluation prior to implantation of a percutaneous trial system and returned one-day postimplant for randomization and initiation of SCS. Three days later, patients were evaluated and crossed over into the alternate treatment group. Final evaluation of patient well-being, pain relief, satisfaction, quality of life, preference, and stimulation sensation occurred on Day 6. Patient preference was assessed using a one-sample Z-test. Treatment and group differences were explored using paired t-test for continuous and ordinal variables and chi-square of Fisher's exact test for categorical variables. RESULTS: More patients (70%) preferred CC stimulation over CV stimulation (30%), and CC stimulation produced a significantly larger decrease in pain scores than CV stimulation. Interestingly, patients initially exposed to CC stimulation were less likely to be satisfied with CV stimulation. CONCLUSIONS: The results from this study indicate that patients preferred and experienced greater satisfaction and pain relief with the CC system during an SCS trial period. Differences between the two systems following long-term use has yet to be compared. However, the benefits of the CC system seen with short-term use should be considered when selecting an SCS system.