34th Annual Scientific Meeting proceedings

Objectives:

Neurostimulation is used to alleviate unmanageable pain in humans but is not reported in horses. Our objective was to describe the safety, efficacy and complications of neurostimulation of the spinal cord and dorsal root ganglion (DRG) in horses.

Methods:

Three client-owned horses with severe orthopedic hindlimb injuries (open fetlock, metatarsal fracture, and severe quadriceps muscle contracture) and two experimental horses under IACUC approval were included. The neurostimulator electrode was placed at the lumbar epidural space using standing sedation and local anesthetic medications (N=3; client-owned) or under general anesthesia (N=2; experimental). Neurostimulator electrodes were positioned at L5 (N=4) or through the neuroforamen over the DRG (N=1) using radiographic guidance. Electrode wires were tunneled and attached to a subcutaneously-implanted generator. Neurostimulation was controlled remotely using proprietary software installed on an iPad. Euthanasia and histologic evaluation were performed on experimental horses.

Results:

The stimulator was placed without complication in all horses. Gradual increases in stimulation ultimately produced local muscle fasciculations. A further reduction in amplitude stopped motor responses, thereby providing sensory modulation only. Implantation sites healed without complication (N=4) or had incisional discharge (N=1). No devices malfunctioned. Two client-owned horses had significant reductions in pain, thereby reducing the need for epidural opioid medications. After improvement of lameness (N=2), one stimulator was removed, while the other was deactivated though remained implanted for four years without complication. Histologic findings showed mild focal inflammation.

Conclusions:

Preliminary results show implantation of neurostimulators in horses is feasible, associated with few adverse events and provides a method of multimodal pain relief.