Introduction

Unlike conventional spinal cord stimulation (SCS)—which employs single pulses delivered at a fixed rate to the dorsal spinal cord—burst SCS uses a fixed rate, five-pulse burst of stimuli as a treatment for chronic pain. The electrical charge per second (i.e., the battery depletion) is three times greater with burst SCS although burst SCS is generally programmed at lower amplitudes compared to conventional SCS.¹ Mechanistic explanations have suggested burst SCS differentially modulates the medial and lateral pain pathways versus conventional SCS.² Differences in neural activation resulting from either burst or conventional SCS may be quantified with the spinal evoked compound action potential (ECAP), an electrical measure of synchronous neural activation. Here, we use ECAPs acquired from both the ALS and dorsal columns in sheep to assess these differences and gain mechanistic insight into both types of SCS.

Materials / Methods

Seven sheep were each implanted with a dorsal stimulation lead at T9/T10, a dorsal ECAP sensing lead at T6/T7, and a lead also at T9/T10 but adjacent to the ALS (Fig. 1). Both burst and conventional SCS with swept stimulation amplitudes up to the visual motor threshold (vMT) were delivered to three different dorsal spinal locations,³ and ECAP thresholds (ECAPTs) were calculated for all combinations.⁴ Then, changes in ALS activation for both types of SCS was assessed using test stimulation delivered to the ALS.

Fig. 1

Results

The ALS ECAP recordings were separated into three different bins per stimulation location for both the burst and conventional dorsal SCS—sub-ECAPT, sub-ECAPT to vMT, and supra-vMT (Fig. 2). In all cases, no significant difference (p > 0.05) was noted between burst and conventional SCS for these three bins for all three stimulation sites. Further, both burst and conventional SCS potentiated ALS ECAPs in an equivalent manner as stimulation amplitudes were increased.

Fig. 2

Discussion

When dosed equivalently relative to the ECAPT—a measure that correlates with the perception threshold—burst SCS does not result in differentially unique changes in ALS activation versus conventional SCS; additionally, burst SCS below the ECAPT does not result in any discernable excitability changes in the neural pathways feeding pain relevant supraspinal sites.

Conclusions

Differences noted previously between burst and conventional SCS results (i.e., in terms of clinical benefit)⁵ may simply result from non-equivalent dosing between these stimulation modalities.

References

¹De Ridder D, Vanneste S, Plazier M, Van Der Loo E, Menovsky T. Burst spinal cord stimulation: Toward paresthesia-free pain suppression. Neurosurgery. 2010;66(5):986-990. doi:10.1227/01.NEU.0000368153.44883.B3

²De Ridder D, Vanneste S. Burst and Tonic Spinal Cord Stimulation: Different and Common Brain Mechanisms. Neuromodulation. 2016;19(1):47-59. doi:10.1111/ner.12368

³Al-Kaisy A, Baranidharan G, Palmisani S, et al. Comparison of Paresthesia Mapping to Anatomical Placement in Burst Spinal Cord Stimulation: Initial Trial Results of the Prospective, Multicenter, Randomized, Double-Blinded, Crossover, CRISP Study. Neuromodulation. 2020;23(5):613-619. doi:10.1111/ner.13104

⁴Pilitsis JG, Chakravarthy K V, Will AJ, et al. The Evoked Compound Action Potential as a Predictor for Perception in Chronic Pain Patients: Tools for Automatic Spinal Cord Stimulator Programming and Control. Front Neurosci. 2021;15:881. doi:10.3389/fnins.2021.673998

⁵Deer T, Slavin K V, Amirdelfan K, et al. Success Using Neuromodulation With BURST (SUNBURST) Study: Results From a Prospective, Randomized Controlled Trial Using a Novel Burst Waveform. Neuromodulation. 2018;21(1):56-66. doi:10.1111/ner.12698

Learning Objectives

1. Differences between burst and conventional SCS; burst SCS consists of a cluster of 5 - 1 ms wide pulses delivered at 40 Hz, while conventional stimulation is a single pulse (but may also be of the same pulsewidth and frequency). Previous mechanistic discussions have described a differentially unique effect of burst SCS on the lateral and medial pain pathway.

2. ECAPs may be used as a quantitative measure of neural activation, not just from the dorsal columns but from the anterolateral tracts as well.

3. When dosed equivalently using ECAPs, no differentially unique effect is noted with burst versus conventional SCS. Mechanistic differences noted previously between burst and conventional SCS may have resulted from non-equivalent dosing between the stimulation paradigms.