Experimental study of adhesive spinal arachnoiditis.

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In this study, we prepared an animal model of spinal adhesive arachnoiditis by injecting Kaolin into the subarachnoid space of rabbits. The animals were sacrificed 4 months later, and changes of the spinal cord and the subarachnoid space were examined. Of the 22 rabbits given Kaolin injection into the cerevrospinal fluid, 3 showed partial obstruction of the subarachnoid space nd 19 showed complete circumferential obstruction. In the rabbits with partial obstruction, intramedullary changes and dilatation of the central canal were not observed. However, among the 19 animals showing complete obstruction, dilatation of the central canal (hydromyelia) occured in 14 and an intramedullary syrinx was observed in 9. In animals with complete obstruction, fluorescence microscopy revealed intramedullary edema around the central canal an extending to the posterior column. Since such changes were not present in animals with only partial obstruction of the subarachnoid space, these changes were not d … More ue to disturbance of the arterial system but rather to impairment of the venous system which is easily affected by increased pressure. Scanning electron microscopy revealed a marked reduction of villi on the ependymal cells lining the dilated central canals. Transmission electron microscopy revealed separation of the ependymal cells. Scanning and transmission electron microscopy of sringomyelia revealed that nerve fibers and nerve cells were exposed on the surface of the syrinx, and there was no clear border with the medullary tissue. Around the syrinx, abnormal verve fibers and nerve cells were observed, and a scavenging necrotic tissue. In other words, since there is little neural regeneration in the spinal cord, it seems that necrotic tissue is removed by macrophages to leave a syrinx (syringomyelia). There are two types of syringomyelia, i.e.hydromyelia, which is dilation of the central canal, and syringomyelia, which is a syrinx with no connection to the central canal. The two types differ in their mechanism of development : hyromyelia is attributed to disturbed reflux of cerebrospinal fluid, while tissue necrosis due to disturbed intramedullary blood flow is considered to be deeply involved in formation of the syrinx in syringomyelia. Less