Automatic adaptation of neurostimulation therapy in response to changes in patient position: Results of the posture responsive spinal cord stimulation (PRS) research study

Abstract

Background: Variation in the intensity of neurostimulation with body position is apractical problem for many patients implanted with a spinal cord stimulation system becausepositional changes may result in overstimulation or understimulation. These posture-relatedchanges in patients' perception of paresthesia can affect therapeutic outcomes of spinalcord stimulation therapy. An accelerometer-based algorithm that automatically adjustsspinal cord stimulation based on sensed body position or activity represents a potentialsolution to the problem of position-mediated variations in paresthesia perception.Objective: The objective of this study was to compare patient satisfaction ratings formanual versus automatic adjustment of spinal cord stimulation amplitude in response topositional changes.Study Design: Prospective, multicenter, open-label, randomized trialSetting: 2 pain centers in the US.Method: Twenty patients at 2 centers in the U.S. who had been implanted with aspinal cord stimulation system for low back and/or leg pain were enrolled in the study.During a 3-day run-in phase, patient position and activity changes were monitored withan ambulatory data recorder and with a research patient programmer which recorded allstimulation parameter changes. Patients who made ≥ 2 amplitude adjustments per 24-hour period were invited to participate in an in-clinic phase. During the in-clinic phase,patients' preferred stimulation amplitude and therapy impedance measured at the preferredstimulation amplitude were determined as they performed a series of 8 physical tasks.Satisfaction ratings were determined during position transitions between the physical tasksusing both manual and automatic adjustments.Results: Among the 15 patients who completed the in-clinic test protocol, overallsatisfaction ratings were significantly higher for automatic adjustment of stimulationamplitudes versus manual adjustments. Patients reported statistically significantimprovements with automatic versus manual adjustment for the standing to supinetransition and for supine to standing transition. Approximately 74% of participants ratedthe paresthesia intensity of the automatic adjustment algorithm as "just right" for thephysical tasks that were completed.Limitations: Small study size.Conclusion: Patients preferred automatic versus manual adjustment of stimulationamplitude in response to changes in paresthesia consequent to positional changes duringin-clinic testing.