A novel rat model of brachial plexus injury with nerve root stumps.

BACKGROUND: The C5-C6 nerve roots are usually spared from avulsion after brachial plexus injury (BPI) and thus can be used as donors for nerve grafting. To date, there are no appropriate animal models to evaluate spared nerve root stumps. Hence, the aim of this study was to establish and evaluate a rat model with spared nerve root stumps in BPI.

NEW METHOD: In rupture group, the proximal parts of C5-T1 nerve roots were held with the surrounding muscles and the distal parts were pulled by a sudden force after the brachial plexus was fully exposed, and the results were compared with those of sham group. To validate the model, the lengths of C5-T1 spared nerve root stumps were measured and the histologies of the shortest one and the corresponding spinal cord were evaluated.

RESULTS: C5 nerve root stump was found to be the shortest. Histology findings demonstrated that the nerve fibers became more irregular and the continuity decreased; numbers and diameters of myelinated axons and thickness of myelin sheaths significantly decreased over time. The survival of motoneurons was reduced, and the death of motoneurons may be related to the apoptotic process.

COMPARISON WITH EXISTING METHOD(S): Our model could successfully create BPI model with nerve root stumps by traction, which could simulate injury mechanisms. While other models involve root avulsion or rupturing by distal nerve transection.

CONCLUSIONS: This model would be suitable for evaluating nerve root stumps and testing new therapeutic strategies for neuroprotection through nerve root stumps in the future.