Department of Orthopaedics and Traumatology, Li Kai Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, PR China.
Clin Neurophysiol. 2011 Jul;122(7):1440-7. doi: 10.1016/j.clinph.2010.12.051. Epub 2011 Feb 16.
Somatosensory-evoked potentials (SEPs) were found to correlate well with the disability and postoperative recovery in patients with cervical spondylotic myelopathy. Yet the exact pathophysiology behind it remains to be elucidated. This study aims to characterise the ultrastructural changes of a chronically compressive spinal cord with various SEP responses in a rat model.
A total of 15 rats were used with surgical implantation of a water-absorbing polymer sheet into the cervical spinal canal on the postero-lateral side, which expanded over time to induce chronic compression in the cord. At postoperative 6 months, the functional integrity of the cords was recorded by SEP responses by comparing injured and non-injured sides, and the ultrastructural integrity was assessed by 7-T magnetic resonance (MR) diffusion imaging, contrast-enhanced micro-computed tomography (μCT) and histological evaluations.
Six rats showed unchanged SEP, and the other nine showed decreased amplitude only (n=5) or delayed latency (n=4). The circulation insults of the cords were found among all the rats, showing central canal enlargement, intra-tissue bleeding or increased blood vessels in the central grey matter. Ultrastructural damage was noted in the rats with changed SEP responses, which was suggested by lower fractional anisotropy and higher contrast intensity radiologically and echoed by less myelin stain and cavitation changes histologically. In the animals with delayed latency, the cord showed significant loss of motoneurons as well as gross appearance distortion.
The categorised SEP responses by amplitude and latency could be an indicator for the extent of ultrastructural damage of the spinal cord after chronic compressive injuries.
The findings built a solid foundation for SEP application in clinical diagnosis and prognostication of spinal cord injuries.
体感诱发电位（SEP）与颈椎病患者的残疾和术后恢复密切相关。然而，其背后的确切病理生理学机制仍有待阐明。本研究旨在通过大鼠模型，对具有不同 SEP 反应的慢性压迫脊髓的超微结构变化进行特征描述。
共使用 15 只大鼠，通过在脊髓后外侧的椎管内植入吸水聚合物片，随着时间的推移，该聚合物片会逐渐扩张，从而导致脊髓慢性受压。术后 6 个月，通过比较损伤侧和未损伤侧的 SEP 反应，记录脊髓的功能完整性，通过 7-T 磁共振（MR）扩散成像、对比增强微计算机断层扫描（μCT）和组织学评估，评估超微结构完整性。
6 只大鼠的 SEP 无变化，另外 9 只大鼠的 SEP 仅出现波幅降低（n=5）或潜伏期延迟（n=4）。所有大鼠均出现脊髓循环损伤，表现为中央管扩大、组织内出血或中央灰质内血管增多。改变 SEP 反应的大鼠出现超微结构损伤，影像学上表现为部分各向异性分数降低和对比强度增加，组织学上表现为少突胶质细胞染色减少和空洞改变。潜伏期延迟的动物，脊髓出现明显的运动神经元丢失和大体外观变形。
通过振幅和潜伏期对 SEP 进行分类，可以作为慢性压迫性损伤后脊髓超微结构损伤程度的指标。
这些发现为 SEP 在脊髓损伤的临床诊断和预后中的应用奠定了坚实的基础。
