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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.

Purpose: To use high-resolution diffusion-weighted and calculated apparent diffusion coefficient (ADC) MR imaging to determine whether fixation and storage influence diffusion anisotropy in white matter tracts of cat spinal cord specimens., Methods: Four cat cord specimens were imaged using a diffusion-weighted spin-echo sequence. Diffusion encoding was applied in the section-select axis (parallel to white matter tracts) and in the read axis (perpendicular to white matter tracts). Five sets of axial diffusion-weighted images were acquired with b values ranging from 0 to 800 s/mm2 and used to obtain calculated ADC images and to determine diffusion coefficients in different regions of the white matter tracts., Results: After cord fixation, a decrease in T2 relaxation and spin density in the white matter caused the signal intensity to appear similar on diffusion-weighted images when the diffusion-probing gradient was applied along both the section-select and read axes. On the calculated ADC images, however, distinct differences in signal intensities were seen in the section-select and read axes., Conclusion: Although there is little difference in signal intensity in the white matter tracts on diffusion-weighted images when diffusion encoding is applied in the section-select or read axis in the fixed specimens, calculated ADC images confirm that diffusion anisotropy is maintained. Therefore, calculated ADC images may be helpful in the evaluation of fixed spinal cord specimens.

Direct carotid-cavernous sinus fistulas that present with signs and symptoms contralateral to the arterial supply of the fistulas are not uncommon. We present a thoroughly documented case of a dural-cavernous sinus fistula with symptoms exclusively contralateral to the arterial source, a rarer entity. The patient presented with a red, proptotic right eye and a history of transient horizontal diplopia and a "feeling of fullness" in that eye. Magnetic resonance imaging (MRI) of the brain and orbits performed at another hospital had shown no abnormalities. Carotid angiography performed on the right side was normal; carotid angiography performed on the left side showed a dural-cavernous sinus fistula, with shunting from branches of the left external carotid artery directly to the right cavernous sinus. Orbital duplex color-flow sonography showed reverse flow in a dilated right superior ophthalmic vein. This unusual manifestation of a dural-cavernous sinus fistula offers insight into the pathophysiology of arteriovenous fistulas involving the cavernous sinus, and is a reminder that bilateral injections are required when performing carotid angiography to characterize these disorders.