Single Collateral Reconstructions Reveal Distinct Phases of Corticospinal Remodeling after Spinal Cord Injury

Spinal cord injuries can disrupt nerve pathways, leading to loss of movement and sensation. In some cases, the nervous system can partially compensate by rewiring itself, a process called axonal remodeling. One important pathway that remodels after spinal cord injury is the corticospinal tract (CST), which controls skilled movements. After injury, the CST can form new connections in the spinal cord, called detour circuits, to bypass the damaged area. This study used advanced techniques to visualize and analyze individual CST connections (collaterals) over time after spinal cord injury in mice, revealing that the remodeling process occurs in three distinct phases: an initial growth phase, a collateral formation phase, and a maturation phase where connections are refined.

• 1
  CST collateral formation begins within the first 10 days after spinal cord injury, and these collaterals can persist for at least 24 weeks.
• 2
  Both major and minor CST components contribute to the formation of these persistent collaterals.
• 3
  CST remodeling occurs in three distinct phases: growth initiation (first 10 days), collateral formation (10 days to 3-4 weeks), and maturation (3-4 weeks to 12 weeks), with each phase characterized by specific changes in collateral structure and connectivity.