EPV001 - CARRY-OVER EFFECTS AND THE EFFECTS OF CYCLING IN AN ANIMAL MODEL OF SPINAL CORD STIMULATION (ID 371)
- Jeffrey Kramer, United States of America
- Louis Vera-Portocarrero, United States of America
- Tina Billstrom, United States of America
- Melanie Goodman Keiser, United States of America
- Jeffrey Kramer, United States of America
Abstract
Introduction
We have validated a large animal model of chronic sensory change to evaluate spinal cord stimulation (SCS) therapy in sheep. Understanding stimulation carry over effects may give us novel ways to deliver therapy and new methods to conserve battery. The present study investigated the carry over effect of stimulation dose and how using different cycling paradigms affected it.
Methods/Materials
A nerve injury was induced in four sheep. Quantitative sensory testing (QST) was performed by application of an automated von Frey filament (1000 g) to the hindlimb of the sheep and measuring the threshold for a response. Sheep were implanted with octopolar leads in lumbar segments of the spinal cord. Stimulation was applied continuously for 8 days with an amplitude of 25% motor threshold (MT) or 50% MT. Testing was performed over the 8 days while stimulation was ON and after turning stimulation OFF. Two separate cycling paradigms (stimulation ON 10% and 50% of total time) were incorporated into stimulation either at the beginning of the stimulation period or after 72 hours of continuous stimulation.
Results
Sheep with nerve injury presented with lower withdrawal thresholds (77% reduction) to von Frey filament application. SCS at 25% MT did not reduce the hypersensitivity. In contrast, SCS delivered at 50% MT was able to reduce hypersensitivity in a biphasic manner over the 8-day period. After stimulation was turned OFF, only the higher amplitude yielded a significant carry-over effect up to 30 minutes following the end of stimulation. A 50% stimulation ON paradigm produced a reduction of hypersensitivity like continuous stimulation, regardless if the cycling started at the beginning or later in the stimulation period. A 10% stimulation ON paradigm did not reduce hypersensitivity in a significant manner nor did it produce a carry-over effect.
Discussion
This study evaluated the behavioral withdrawal response to clinically relevant parameters in a large animal model. Continuous stimulation over 8 days attenuated hypersensitivity in sheep and it was still effective after stimulation was OFF only when a higher amplitude was used. Cycling yielded similar attenuation overall, but only had a carry-over effect with a higher duty cycle. This study provides evidence that continuous stimulation might not be necessary to reverse pain behaviors in our large animal model of SCS therapy. These results could have implications in extending battery life and help in reducing constant recharging by patients.
Conclusions
Higher amplitude and duty cycle yielded effectiveness and a carry-over effect.
