Chronic changes in cerebrospinal fluid pathways produced by subarachnoid kaolin injection and experimental spinal cord trauma in the rabbit: their relationship with the development of spinal deformity. An electron microscopic study and magnetic resonance imaging evaluation

Abstract

Post-traumatic cystic changes in cerebrospinal fluid (CSF) pathways such as ventriculomegaly and/or hydrosyringomyelia are not uncommon, but their characteristics have not yet been fully clarified. This study was designed to investigate the alterations affecting the CSF pathways in rabbits at a late stage, and to clarify the relationship between these changes and the development of spinal deformity. In this study, a total of 60 New Zealand white rabbits were used and they were segregated into four different groups of 15 animals each: sham-operation group, kaolin group, and kaolin plus mild trauma group and kaolin plus severe trauma group. The animals were subjected to radiological investigation using direct X-ray study and magnetic resonance imaging (MRI) after 4 months. The thoracic spinal cords of the animals were dissected after intracardiac perfusion-fixation with 10% formalin for light microscopy and 2.5% glutaraldehyde for transmission electron microscopic study. Following the sectioning and staining procedures, the histological characteristics of the spinal cords were evaluated with light microscopy and transmission electron microscopy. A spinal deformity developed in 90% in rabbits in both kaolin injection group and spinal trauma groups. MRI revealed generalized dilatation of the ventricular system and the central canal of the spinal cord after the kaolin injection with/without trauma in this study. Gross morphologic examination showed some enlargement of entire CSF pathways in these groups. All animals with central canal dilatation had mild or severe scoliotic and kyphotic deformities. In a light microscopic study, a denuded ependymal line and multicyst formations in periependymal areas were found in both kaolin injection and spinal trauma groups. Ultrastructurally, an apical flattening of the ependyma, microcysts in the ependymal cells, axonal degeneration, demyelination, and loss of ependymal cells adjacent mild spongy were found in the spinal cords of animals in these groups. To the best of our knowledge, this is the first study to investigate the chronic effects of spinal cord injury (SCI) on the CSF pathways and their relationship with the development of spinal deformity in an experimental model of kaolin injection and trauma, using MRI as well as light and transmission electron microscopy. In the light of this study, the severity of spinal cord injury on the development of some degenerative findings in the spinal cord was clear, but further clinical and experimental studies using dynamic imaging techniques will be valuable.