Pronounced species divergence in corticospinal tract reorganization and functional recovery after lateralized spinal cord injury favors primates

Sci Transl Med, 2015 · DOI: 10.1126/scitranslmed.aac5811 · Published: August 26, 2015

Spinal Cord Injury Neurology Research Methodology & Design

Simple Explanation

This study investigates why primates often show better recovery after spinal cord injuries that affect one side of the body more than the other. Researchers compared recovery in over 400 quadriplegic patients with varying degrees of spinal cord damage laterality. The study found that greater asymmetry in spinal cord damage correlated with better functional gains. They also compared outcomes in rats and monkeys with similar injuries, finding that monkeys and humans showed greater recovery of locomotion and hand function than rats. The researchers suggest this difference is due to how the corticospinal tract, a major motor pathway, reorganizes after injury. In primates, this tract forms detour circuits that help reconnect the brain to muscles below the injury, which are less pronounced in rodents.

Study Duration

1 Year

Participants

437 quadriplegic patients, rats, and monkeys

Evidence Level

Not specified

Key Findings

1
Functional gains increased with the laterality of spinal cord damage in humans.
2
Monkeys and humans showed greater recovery of locomotion and hand function than rats after lateralized spinal cord injury.
3
Recovery correlated with the formation of corticospinal detour circuits below the injury, which were extensive in monkeys, but nearly absent in rats.

Research Summary

The study investigated inter-species differences in recovery after lateralized spinal cord injury (SCI), focusing on the corticospinal tract reorganization. The researchers found that functional recovery in humans correlated with the laterality of SCI and that monkeys and humans showed greater recovery compared to rats. The study highlights the importance of primate models in translational research due to the unique response of the primate corticospinal tract after injury.

Practical Implications

Clinical Trial Design

The degree of laterality should be carefully considered for the selection of homogenous patient cohorts for clinical trials, as it influences functional outcomes.

Therapeutic Development

The study re-emphasizes the importance of developing therapies that target regeneration and sprouting of the corticospinal tract in humans.

Primate Models

The results reinforce the need for continuing the development of nonhuman primate models for translational SCI research.

Study Limitations

1
Generalization of findings to other types of incomplete injuries is unclear.
2
Ethical and societal hurdles related to primate experiments slow broad implementation.
3
Cost and experimental complexity of primate experiments pose challenges.

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