A continuous spinal cord stimulation model attenuates pain-related behavior in vivo following induction of a peripheral nerve injury.

OBJECTIVES

Models that simulate clinical conditions are needed to gain an understanding of the mechanism involved during spinal cord stimulation (SCS) treatment of chronic neuropathic pain. An animal model has been developed for continuous SCS in which animals that have been injured to develop neuropathic pain behavior were allowed to carry on with regular daily activities while being stimulated for 72 hours.

MATERIAL AND METHODS

Sprague-Dawley rats were randomized into each of six different groups (N = 10-13). Three groups included animals in which the spared nerve injury (SNI) was induced. Animals in two of these groups were implanted with a four-contact electrode in the epidural space. Animals in one of these groups received stimulation for 72 hours continuously. Three corresponding sham groups (no SNI) were included. Mechanical and cold-thermal allodynia were evaluated using von Frey filaments and acetone drops, respectively. Mean withdrawal thresholds were compared. Statistical significance was established using one-way ANOVAs followed by Holm-Sidak post hoc analysis.

RESULTS

Continuous SCS attenuates mechanical allodynia in animals with neuropathic pain behavior. Mechanical withdrawal threshold increases significantly in SNI animals after 24 and 72 hours stimulation vs. SNI no stimulation (p = 0.007 and p < 0.001, respectively). SCS for 24 and 72 hours provides significant increase in mechanical withdrawal thresholds relative to values before stimulation (p = 0.001 and p < 0.001, respectively). Stimulation did not provide recovery to baseline values. SCS did not seem to attenuate cold-thermal allodynia.

CONCLUSION

A continuous SCS model has been developed. Animals with neuropathic pain behavior that were continuously stimulated showed significant increase in withdrawal thresholds proportional to stimulation time.