A rodent model of chronic compressive cervical myelopathy

Degenerative chronic spinal cord compression induced cervical myelopathy is a common cause of spinal cord dysfunction. The disease generally leads to impairment of the sensory and motor function of the cord progressively and insidiously. However, the underlying pathophysiology and the precise mechanism of the disease are still uncertain and remain to be investigated. The establishment of an animal model which reproduces the clinical condition of cervical myelopathy would be helpful for better understanding to the disease. In this study, a rat model of chronic spinal cord compression was developed by implantation of water-absorbing polymer at the lateral side of the spinal canal. The structural and functional change of the spinal cord due to compression were then assessed with different techniques - Magnetic Resonance Imaging (MRI) for the structural assessment, and motor behavioral scoring and somatosensory-evoked potential (SSEP) for the functional evaluation. From the MR images the frac14-lateral compression ratios are computed. The result shows that the compression is significant by compared with the compression ratios of the adjacent levels (p< 0.01). However, the severe changes of SSEP did not show a close correlation with the compression ratios, suggesting that MRI findings are not automatically associated with functional deficits in spinal cord. Further classification of animal based on SSEP response shows that latency delay was more severe with higher categories. It is suggested that changes in latency might be a prognosis for the surgical outcome, which animals in higher categories may have higher chance to have permanent loss of spinal cord function.