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.
Key words: spinal cord stimulation, automaticity, paresthesia, neuromodulation,
neurostimulation, adaptive stimulation, posture responsive stimulation, accelerometry
Automatic Adaptation of Neurostimulation
Therapy in Response to Changes in Patient
Position: Results of the Posture Responsive
Spinal Cord Stimulation (PRS) Research Study