Objective: To study the recovery and mechanism of nerve root under variable chronic injury and to determine the alerting index of the evoked potential of the irreversible injury to the nerve root, so as to offer the evidence for selecting treatment methods, judging prognosis and grasping treatment juncture.
Methods: Autogenous cancellous bones were planted into the right C7-8 and C8-T1 intervertebral foramens in 30 cats with weight 3-5 kg to make chronic injury models. The left side was for auto-contrast. By 24 weeks' observation and dynamic supervisory of evoked potential, the injury degrees were ascertained and classified into I to V degree groups. Then the operation of decompression was performed on every group. During the following 32 weeks, the evoked potential survey and pathological tissue examination were made every week to observe the function recovery of the injured roots.
Results: The tissue form and function of the nerve roots with I and II degree injuries recovered well within 2 to 6 weeks. Those with II degree injury began to recover in the 4th week, and gradually recovered to normal 12 weeks later. In the group of IV degree injury, the recovery was slow. They could recover completely in 3 of 6 cats, partly in 2 and hardly recovered in 1. The function and tissue form of nerve roots with V degree injury could hardly recovered.
Conclusion: In the case that the compression has been removed before the nerve roots suffer II degree injury. The tissue form and function of the nerve roots will recovered satisfactorily, whereas they may suffer irreversibly injury by IV degree injury, and even can hardly recover by V degree injury. During the supervisory process of the recovery of the injured nerve roots, sensitive evoked potential is a sensitive sign of early recovery and motion evoked potential is a reliable sign of recovery extent.