Original contributions
Postural Changes in Spinal Cord Stimulation Perceptual Thresholds

https://doi.org/10.1111/j.1525-1403.1998.tb00013.xGet rights and content

ABSTRACT

Introduction.

Spinal cord stimulation voltage thresholds have been observed to change with body position, but previously have not been characterized in detail.

Design.

Prospective case series.

Methods.

We have obtained voltage measurements at the threshold of perception in three body postures for patients with percutaneous dorsal epidural leads.

Results.

In our sample of 42 patients, we observed a significant (p = 0.000) increase in voltage requirements when moving from supine to sitting or standing positions. This increase can be represented as a linear slope (1.25) across a range of baseline voltage amplitudes. Ninety-five percent of patients experienced an increase, primarily between 11 and 25%.

Conclusions.

These observations have implications for the design, implantation, and clinical application of spinal cord stimulators.

Section snippets

INTRODUCTION

Spinal cord stimulation (SCS) for chronic, intractable pain is subject to postural effects, which have not been fully characterized(1). We have previously reported that, at long-term follow-up, the majority of our patients reported changes in perceived stimulation amplitude, requiring adjustment, with changes in body position, specifically apparent amplitude changes with movement from a standing to a lying position(2).

We have undertaken a study to address the following questions: Does body

METHODS

Our study subjects were patients with chronic, intractable low back and leg pain admitted to The Johns Hopkins Hospital (Baltimore, MD) for implantation of a temporary dorsal epidural stimulating electrode. All patients met standard clinical criteria for spinal cord stimulation and all gave informed consent under institutional guidelines. The electrode was placed percutaneously via a T12-L1 or L1–2 interlaminar Tuohy needle puncture and tested at positions from T8 to T12. Test stimulation was

RESULTS

As shown in Fig. 1, sitting and standing thresholds were higher than supine thresholds; linear regression models yielded slopes of 1.250 and 1.252, respectively. The mean voltage differences from supine to sitting positions and from supine to standing positions were respectively 0.726 and 0.728. By paired, two-sided t-test, these differences were both found to be statistically significant (p = 0.000), but no significant difference was observed between sitting and standing positions.

As shown in

DISCUSSION

Postural effects on spinal cord stimulation have been appreciated for many years, but have never been fully characterized. Barolat et al. have recognized this effect implicitly in their studies of stimulation thresholds: “Because the distance between the nerve fibers and the electrode is a significant contributing factor for changes in the perception threshold(3), the patient was always in supine position during the testing.” (4)

Holsheimer et al. have developed models to explain this, beginning

CONCLUSIONS

The perceptual threshold of stimulation paresthesias is directly related to body position in our patients with temporary dorsal epidural electrodes. We have observed not only wide variability (between patients) of baseline perceptual thresholds in supine position, but also wide variability in threshold changes as patients move to a sitting or standing position. Overall, these postural changes conform to a linear regression model.

ACKNOWLEDGMENTS

The authors are grateful for comments by Mike Schendel, Medtronic Inc., Minneapolis, MN. This is a pilot study for which no outside financial support was requested or received.

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Copyright © 1998 International Neuromodulation Society. Published by Elsevier Inc. All rights reserved.