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Background and Purpose: Although high-resolution MR imaging is a valuable diagnostic tool, in vivo MR imaging has not yet been compared with in vitro MR imaging and histologic techniques following experimental spinal cord injury (SCI). The goal of the present study was to evaluate the feasibility of using in vivo MR imaging, in vitro MR imaging, and histologic techniques to study pathologic changes associated with excitotoxic SCI at a single time point. These results are important for future research using in vivo MR imaging to study the temporal profile of pathologic changes following SCI., Methods: Rats received intraspinal injections of quisqualic acid at the T12-L2 spinal level. In vivo T1- and T2-weighted and dynamic contrast-enhanced MR images were collected 17-24 days postinjury. Once completed, spinal cords were removed and in vitro MR microscopy and histologic assessment were performed. MR images were collected using 4.7-T (in vivo) and 14.1-T magnets (in vitro)., Results: Pathologic changes--including hemorrhage, neuronal loss, cavities, and central canal expansion--were visible in T2-weighted in vivo MR images. Evaluation of the blood-spinal cord barrier after injury with contrast agent enhancement showed no disruption at the time points evaluated. In vitro MR images and histologic evaluation confirmed pathologic details observed in vivo., Conclusion: Results show that high-resolution in vivo MR imaging has the potential to be used in studying the progression of pathologic changes at multiple time points following SCI. This strategy may provide a way of studying structure-function relationships between therapeutic interventions and different pathologic characteristics of the injured spinal cord.

Background and Purpose: Spinal cord injury (SCI) results in a number of consequences; one of the most difficult to manage is chronic neuropathic pain. Thus, defining the potential neural and biochemical changes associated with chronic pain after SCI is important because this may lead to development of new treatment strategies. Prior studies have looked at the thalamus, because it is a major sensory relay station. The purpose of our study was to define alterations in metabolites due to injury-induced functional changes in thalamic nuclei by using single-voxel stimulated echo acquisition mode MR spectroscopy., Methods: Twenty-six men were recruited: 16 patients with SCI and paraplegia (seven with pain, nine without pain) and 10 healthy control subjects. Pain was evaluated in an interview, which included the collection of information concerning the location, quality, and intensity of pain, carefully identifing the dysesthetic neuropathic pain often seen in SCI. Localized single-voxel (8-cm(3) volume) proton spectra were acquired from the left and right thalami., Results: The concentration of N-acetyl (NA) was negatively correlated with pain intensity (r = -0.678), and the t test showed that NA was significantly different between patients with pain and patients without pain (P =.006). Myo-inositol was positively correlated with pain intensity (r = 0.520); difference between patients with pain and those without pain was almost significant (P =.06)., Conclusion: The observed differences in metabolites in SCI patients with and pain and in those without pain suggest anatomic, functional, and biochemical changes in the thalamic region.

Background and Purpose: Recent experimental data have shown that an increase of excitatory amino acids and the initiation of inflammatory responses within the injured spinal cord may play a role in post-traumatic syringomyelia. The purpose of this study was to determine whether diffusion-weighted MR imaging with apparent diffusion coefficient (ADC) maps could provide earlier 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 alpha-amino-3 hydroxy-5 methyl-4 isoxazole propionic acid/metabotropic receptor agonist quisqualic acid. Animals were sacrificed at 1, 4, or 8 weeks after injection, and the spinal cords were fixed in formalin for 1 week and imaged with T1-, T2-, and diffusion-weighted sequences. One control specimen was also imaged. ADC maps were constructed from the diffusion-weighted data. Histopathologic analyses of sections stained with cresyl violet were compared with the MR images., Results: By 1 week after injection, ADC maps at the level of injection showed areas within the gray matter of increased intensity and increased ADC values as compared with the control specimen. These bright areas corresponded to cysts or cavities within the cord parenchyma on the histopathologic sections. The ADC values within affected gray matter areas progressively increased at 4 and 8 weeks, also corresponding to cyst formation. Conventional T1- and T2-weighted images showed corresponding lesions with cystic characteristics at 4 and 8 weeks, but 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 before they were seen on conventional T1- and T2-weighted images.