Role of Active Cerebrospinal Fluid Transport in Syrinx Formation: An Experimental Study on a Model of Chronic Tonsillar Herniation in Rats

Summary

To identify a definite causal relationship between tonsillar herniation and syringomyelia, the dynamics of the cerebrospinal fluid in an animal model of syringomyelia caused by chronic tonsillar herniation was studied. In ten rats of the chronic tonsillar herniation model, 20% wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) solution was continuously injected into the lateral ventricle for 24h using an osmotic pump. After injection, the rats were killed and electron and light microscopic analysis was performed. Four normal rats were subjected to the same surgical procedures for controls. In six of ten rats, all experimental steps were successfully performed, and tonsillar herniations were observed in two rats. In these two rats, WGA-HRP was found in the luminal space of the dilated central canal, inside the ependymal cells, and in the swollen astrocytic processes in the dorsal gray matter, reaching to the dorsal column. In the control group and four transplanted rats without tonsillar herniations, no WGA-HRP was detected in the spinal cord. It is apparent that, in the rats with tonsillar herniations, cerebrospinal fluid flowed into the central canal and was transported into the astrocytes through the ependymal cells.