Diffusion-weighted MR imaging in a rat model of syringomyelia after excitotoxic spinal cord injury

BACKGROUND AND PURPOSE: Recent experimental data have shown that an increas e of excitatory amino acids and the initiation of inflammatory responses wi thin the injured spinal cord may play a role in post-traumatic syringomyeli a, The purpose of this study was to determine whether diffusion-weighted MR imaging with apparent diffusion coefficient (ADC) maps could provide earli er evidence of spinal cord cavitation in a rat model of syringomyelia than available with conventional MR imaging. METHODS: The spinal cord gray matter of four rats was injected with the alp ha-amino-3 hydroxy-5 methyl-4 isoxazole propionic acid/metabotropic recepto r agonist quisqualic acid, Animals were sacrificed at 1, 4, or 8 weeks afte r injection, and the spinal cords were fixed in formalin for 1 week and ima ged with T1-, T2-, and diffusion-weighted sequences, One control specimen w as also imaged, ADC maps were constructed from the diffusion-weighted data, Histopathologic analyses of sections stained with cresyl violet were compa red with the MR images. RESULTS: By 1 week after injection, ADC maps at the level of injection show ed areas within the gray matter of increased intensity and increased ADC va lues as compared with the control specimen, These bright areas corresponded to cysts or cavities within the cord parenchyma on the histopathologic sec tions. The ADC values within affected gray matter areas progressively incre ased at 4 and 8 weeks, also corresponding to cyst formation, Conventional T 1- and T2-weighted images showed corresponding lesions with cystic characte ristics at 4 and 8 weeks, hut not at 1 week. CONCLUSION: In an animal model of syringomyelia, diffusion-weighted imaging with ADC maps detected cystic lesions within spinal cord gray matter befor e they were seen on conventional T1- and T2-weighted images.