C Wen

Somatosensory-evoked potentials as an indicator for the extent of ultrastructural damage of the spinal cord after chronic compressive injuries in a rat model

OBJECTIVEnSomatosensory-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.nnnMETHODSnA 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.nnnRESULTSnSix 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.nnnCONCLUSIONSnThe 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.nnnSIGNIFICANCEnThe findings built a solid foundation for SEP application in clinical diagnosis and prognostication of spinal cord injuries.

A knowledge based automatic region of interest (ROI) segment of cervical cord diffusion tensor imaging

Diffusion MR imaging technique has been developed in past decade to permit the detection of tissue water molecular diffusion at microscopic dimension and has been widely used to investigate the spinal cord parenchyma. The commonly used hand-drawn region of interest (ROI)-based segmentation in diffusion tensor imaging(DTI) analysis is highly labor-intensive and user-dependent. In this study, we aim to develop an automatic template (auto-template) based on anatomy knowledge and computational intelligence to extract the regional diffusion anisotropy pattern of cervical spinal cord. A total of 16 healthy volunteers were recruited in this study. Eleven axial diffusion tensor MR images covering C1 to C7 of cervical spinal cord were taken with single-shot spin-echo echo-planar imaging sequence on a 3T MR system. The fractional anisotropy (FA) value of anterior, lateral, posterior column of white matter and gray matter was measured using hand-drawn ROI and knowledge based computational intelligence method respectively. Knowledge based template showed the FA value in the anterior (0.737±0.009), lateral (0.827±0.011), posterior (0.854±0.007) column of white matter and gray matter (0.493±0.009) with higher inter-rater agreement than hand-drawn ROI method. The result suggested that knowledge based template is a convenient tool to extract the diffusion data in various parts of the cervical spinal cord with high accuracy and inter-rater reliability.