Spinal cord stimulation (scs) improves decreased physical activity induced by nerve injury.

Abstract

Spinal cord stimulation (SCS) is used to manage treatment of neuropathic pain to reduce pain and hyperalgesia and to improve activity. Prior studies using animal models of neuropathic pain have shown that SCS reduces hyperalgesia; however, it is unclear whether SCS affects physical activity. Therefore, we tested whether nerve injury (spared nerve injury [SNI] model) reduced physical activity levels, and whether SCS could restore these decreased activity levels. We tested whether SCS given over a long duration (6 hr daily for 3 months) remained effective. We compared SNI with uninjured controls over 4 weeks, and SNI with sham SCS with SNI with active SCS (4 or 60 Hz at 90% motor threshold). We confirmed the presence of mechanical hyperalgesia by examining mechanical thresholds of the paw with von Frey filaments. Physical activity levels were monitored over 30 min in an automated activity chamber as follows: overall activity, distance traveled, grooming behaviors, and rearing. Measures were taken during SCS every 1-2 weeks for 3 months. Animals with SNI (and no or sham SCS) showed decreased withdrawal thresholds ipsilaterally and reduced physical activity (rearing, distance, lines crossed) for 3 months. Both 4- and 60-Hz SCS increased paw withdrawal threshold during and immediately after SCS through 3 months. Both 4- and 60-Hz SCS increased the overall activity (lines crossed), distance traveled, and rearing, but not grooming behaviors for 3 months. This effect remained similar across the 3 months. Thus, measurement of spontaneous physical activity could be useful to examine nocifensive behaviors after nerve injury and is sensitive to SCS.

Changes in Dorsal Root Ganglion Gene Expression in Response to Spinal Cord Stimulation

“…Nevertheless, clinically, these results are indicative of an effective treatment. The behavioral results are consistent with previous studies, 12,13 done under different stimulation conditions, allowing us to draw connections between genetic changes and behavioral responses regarding injury status and SCS-induced analgesia.…”

Lack of Analgesic Synergy of the Cholecystokinin Receptor Antagonist Proglumide and Spinal Cord Stimulation for the Treatment of Neuropathic Pain in Rats

“…A number of prior studies show SCS reduces mechanical hyperalgesia in animal models of neuropathic pain , similar to that observed in the current study. There was no effect of SCS or proglumide on activity levels, which is in contrast to our prior study . The lack of SCS effect on activity levels may be related to the duration of stimulation since our prior studies showing an improvement in activity were done with much longer stimulation (six hours) , and/or over multiple days (four days–three months) .…”

“…We previously show nerve injury reduces distance traveled, number of crossings, and rearing which we interpret as reduced function . SCS returns these behaviors toward normal .…”

A Continuous Spinal Cord Stimulation Model Attenuates Pain-Related Behavior In Vivo Following Induction of a Peripheral Nerve Injury

“…reported studies in which animals subjected to spinal nerve ligation injury model were stimulated each day for six‐hour sessions over several weeks . In one of the studies , both 4 Hz or 60 Hz stimulating pulses significantly reversed mechanical sensitivity on each day of testing throughout the duration of the study (three months). With six hours of stimulation and 18 hours off time, withdrawal threshold returned to approximately 20% of baseline values.…”