Using evoked compound action potentials to quantify differential neural activation with burst and conventional, 40 Hz spinal cord stimulation in ovines.

Abstract

Unlike conventional dorsal spinal cord stimulation (SCS)-which uses single pulses at a fixed rate-burst SCS uses a fixed-rate, five-pulse stimuli cluster as a treatment for chronic pain; mechanistic explanations suggest burst SCS differentially modulate the medial and lateral pain pathways vs conventional SCS. Neural activation differences between burst and conventional SCS are quantifiable with the spinal-evoked compound action potential (ECAP), an electrical measure of synchronous neural activation.

Methods: We implanted 7 sheep 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 anterolateral system (ALS). Both burst and conventional SCS with stimulation amplitudes up to the visual motor threshold (vMT) were delivered to 3 different dorsal spinal locations, and ECAP thresholds (ECAPTs) were calculated for all combinations. Then, changes in ALS activation were assessed with both types of SCS.

Results: Evoked compound action potential thresholds and vMTs were significantly higher (P < 0.05) with conventional vs burst SCS, with no statistical difference (P > 0.05) among stimulation sites. However, the vMT-ECAPT window (a proxy for the useable therapeutic dosing range) was significantly wider (P < 0.05) with conventional vs burst SCS. No significant difference (P > 0.05) in ALS activation was noted between conventional and burst SCS.

Conclusion: When dosed equivalently, no differentially unique change in ALS activation results with burst SCS vs conventional SCS; in addition, sub-ECAPT burst SCS results in no discernable excitability changes in the neural pathways feeding pain relevant supraspinal sites.