Neurorestoratology evidence in an animal model with cervical spondylotic myelopathy

Cervical spondylotic myelopathy (CSM) is a chronic compression injury of the spinal cord, with potentially reversible conditions after surgical decompression, and a unique model of incomplete spinal cord injury. Several animal studies showed pathological changes of demyelination, axon loss and neuron apoptosis in rats with chronic spinal cord compression. However, there is a limited understanding of the neurological change in the spinal cord after surgical decompression. The aim of this study was to validate the neurorestoratology of myelopathic lesions in the spinal cord in a rat model.

A total of 16 adult Sprague-Dawley rats were divided into four groups: sham control (group 1); CSM model with 4-week chronic compression (group 2), 2 weeks (group 3) and 4 weeks (group 4) after surgical decompression of CSM model. The compression and decompression were verified by magnetic resonance imaging (MRI) test. Neurological function was evaluated by Basso, Beattie, and Bresnahan (BBB) locomotor rating scale, ladder rung walking test and somatosensory-evoked potentials (SEPs). Neuropathological change was evaluated by histological examinations.

MRI confirmed the compression of the cervical spinal cord as well as the reshaping of cord morphology after decompression. After decompression, significant changes of neurological function were observed in BBB scores (p < 0.01, F = 10.52), ladder rung walking test (p < 0.05, F = 14.21) and latencies (p < 0.05, F = 5.76) and amplitudes (p < 0.05, F = 3.8) of SEP. Neuronal degeneration was obvious in the ventral horn with gradual restoration. After decompression, the motor neuron number in the ventral horn did not show significant changes (p > 0.05). However, increasing trend of myelin area and staining intensity were observed in all columns of the white matter (p < 0.05) after decompression, especially in the compressed lateral column.

The established rat model is able to simulate histopathological characteristics of cervical myelopathy in human beings. The neuropathological change demonstrated that neurorestoratology in the myelopathic spinal cord would probably attribute to axonal remyelination of the white matter, but there would be an incapability of neuronal regeneration.