A Rat Model of Chronic Syringomyelia by Epidural Compression of the Lumbar Spinal Cord

Abstract

Introduction There has been no established animal model of syringomyelia associated with lumbosacral spinal lipoma. The research on pathophysiology of syringomyelia has been focused on Chiari malformation, trauma, and inflammation. To help understand the underlying pathophysiology of syringomyelia associated with occult spinal dysraphism, a novel animal model for the syringomyelia by chronic mechanical compression of the lumbar spinal cord was attempted.

Methods The model was made by epidural injection of highly-concentrated paste-like kaolin after partial laminectomy of L1 and L5 level. Behavioral outcome in terms of motor (Basso-Beattie-Bresnahan score) and urinary function was assessed until 12 weeks. Magnetic resonance images (MRI) were used to confirm the formation of syrinx and its extent, and various immunohistochemistry (IHC) studies including GFAP, ED-1, CC1, NeuN, caspase-3, and LFB were done to evaluate the degrees of inflammatory reaction, demyelination, and cell death.

Results By 12 weeks after the operation, syringomyelia formation was confirmed in 85% of the rats (34 out of 40) on H & E staining and MRI. Motor deficit of variable degree was seen immediately after the procedure in 28% (11 out of 40) of the rats. In 13 rats (33%), lower urinary tract dysfunction was seen. Motor deficit improved until 5 weeks after the operation, whereas majority of the urinary deficit improved in the first 2 weeks. There was delayed mortality of 13% (5 out of 40), later than 1 month after the operation and 3 of the 5 died from new onset urinary dysfunction. Serial MRI (n = 1) revealed that prominent syringomyelia was visible 2 months after the operation, and that the syrinx cavities were located proximal to the compression. At 12 weeks after the operation, IHC showed no increase of inflammation or demyelination in these models, compared to sham operation cases.

Conclusions A novel experimental model for the syringomyelia by epidural compression of the lumbar spinal cord has been established. It will serve as an important research tool to elucidate the pathogenesis of this type of syringomyelia, and the CSF hydrodynamics of the lumbar spinal cord.