Automatic adaptation of neurostimulation therapy in response to changes in patient position: results of the Posture Responsive Spinal Cord Stimulation (PRS) Research Study.

BACKGROUND Variation in the intensity of neurostimulation with body position is a practical problem for many patients implanted with a spinal cord stimulation system because positional changes may result in overstimulation or understimulation. These posture-related changes in patients' perception of paresthesia can affect therapeutic outcomes of spinal cord stimulation therapy. An accelerometer-based algorithm that automatically adjusts spinal cord stimulation based on sensed body position or activity represents a potential solution to the problem of position-mediated variations in paresthesia perception. OBJECTIVE The objective of this study was to compare patient satisfaction ratings for manual versus automatic adjustment of spinal cord stimulation amplitude in response to positional changes. STUDY DESIGN Prospective, multicenter, open-label, randomized trial SETTING 2 pain centers in the US. METHOD Twenty patients at 2 centers in the U.S. who had been implanted with a spinal 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 with an ambulatory data recorder and with a research patient programmer which recorded all stimulation 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 preferred stimulation amplitude were determined as they performed a series of 8 physical tasks. Satisfaction ratings were determined during position transitions between the physical tasks using both manual and automatic adjustments. RESULTS Among the 15 patients who completed the in-clinic test protocol, overall satisfaction ratings were significantly higher for automatic adjustment of stimulation amplitudes versus manual adjustments. Patients reported statistically significant improvements with automatic versus manual adjustment for the standing to supine transition and for supine to standing transition. Approximately 74% of participants rated the paresthesia intensity of the automatic adjustment algorithm as "just right" for the physical tasks that were completed. LIMITATIONS Small study size. CONCLUSION Patients preferred automatic versus manual adjustment of stimulation amplitude in response to changes in paresthesia consequent to positional changes during in-clinic testing.