Extensive Spontaneous Plasticity of Corticospinal Projections After Primate Spinal Cord Injury

Nat Neurosci, 2010 · DOI: 10.1038/nn.2691 · Published: December 1, 2010

Simple Explanation

This study investigates how the brain and spinal cord can recover after a spinal cord injury in adult monkeys. Researchers found that the brain's connection to the spinal cord, called corticospinal projections, can significantly repair itself after injury. After a partial spinal cord injury, the monkeys regained about 60% of the original nerve fiber density due to the growth of new connections. This regrowth was linked to improvements in their ability to move, use their hands, and walk. These findings suggest that the brain has a greater ability to heal itself than previously thought, especially in primates. This could lead to new treatments that encourage nerve regrowth and improve recovery after spinal cord injuries in humans.

Study Duration

24 Weeks

Participants

14 naïve rhesus monkeys

Evidence Level

Level II, Experimental study in primates

Key Findings

1
After a C7 spinal cord hemisection in adult rhesus monkeys, corticospinal projections exhibited remarkable spontaneous plasticity, with reconstitution of approximately 60% of pre-lesion axon density.
2
The observed anatomical recovery was associated with significant improvement in coordinated muscle recruitment, hand function, and locomotion in the affected monkeys.
3
Principal components analysis revealed a strong statistical correlation between the sprouting of corticospinal axons and functional improvement of the affected forelimb during both locomotion and food retrieval tasks.

Research Summary

The study demonstrates substantial spontaneous plasticity of corticospinal axons in primates after spinal cord injury, restoring axon density to 60% of normal levels. This axonal regeneration correlates with significant improvements in hand function and locomotion, suggesting a potential mechanism for functional recovery after incomplete SCI. The findings highlight the translational relevance of primate models in SCI research, emphasizing the importance of corticospinal system plasticity for recovery of voluntary movement.

Practical Implications

Therapeutic Target Identification

Identify cellular mechanisms underlying spontaneous corticospinal axon growth to enhance sprouting or induce regeneration.

Improvement of Rodent Models

Partial lesion models in rodents that spare more corticospinal axons could better mimic human SCI recovery.

Understanding Human SCI Recovery

Spontaneous sprouting of corticospinal axons may explain functional improvement after incomplete human SCI.

Study Limitations

1
The study used a specific type of spinal cord injury (C7 hemisection) in rhesus monkeys, which may not fully represent the diverse range of SCI in humans.
2
The study focused primarily on corticospinal projections, and further research is needed to dissect the relative contributions of other systems (e.g., propriospinal) to functional recovery.
3
The exact cellular and molecular mechanisms driving the observed spontaneous axonal plasticity remain to be fully elucidated.

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