Recovery of Motor Function via Intraspinal Detour Circuits following Unilateral Spinal Cord Injury

Introduction: Neuroplasticity is the ability of the central nervous system (CNS) to adapt structurally and functionally in response to motor and sensory dysfunction caused by injury and disease. Spinal interneurons are key components of neuroplastic changes that ameliorate impaired motor function after CNS injury. A lateral spinal cord hemisection model exhibited spontaneous motor recovery of the hind limb on the affected side. Hence, neuroplastic changes within the spinal cord on the affected and/or unaffected side may occur during motor recovery following unilateral spinal cord injury (SCI). However, it remains unclear how the spinal neurons on the affected and unaffected side contribute to motor recovery in the ipsilesional hind limb following unilateral SCI. Thus, we aimed to explore whether the thoracic spinal neurons above the lesion were involved in the motor recovery of the ipsilesional hind limb.

In our SCl model, unilateral lesions were made at the tenth thoracic vertebral level.

Following unilateral SCI, hind limb motor function on the ipsilateral side was initially impaired but showed spontaneous recovery in the behavioral tests, which was subsequently lost after ablation of thoracic spinal neurons in the ipsilesional spinal cord above the lesion. In contrast, changes in the ipsilesional hind limb motor function were not observed after ablation of the contralesional thoracic spinal neurons.

These results suggest that thoracic spinal neurons on the ipsilesional side above the lesion are key components for hind limb motor recovery in a model of unilateral SCI.