Background and purpose: MR imaging and contrast-enhanced MR angiography have been used to detect evidence of spinal dural arteriovenous fistulae (AVF); however, the sensitivity and specificity of these techniques have not been shown. The purpose of this study was to establish the sensitivity, specificity, and accuracy of MR imaging alone compared with MR imaging plus MR angiography in determining whether dural AVF are present and to establish the accuracy of MR angiography in predicting fistula level.
Methods: Twenty patients with surgically proven dural AVF (diagnosed with radiographic digital subtraction angiography) and 11 control patients who had normal digital subtraction angiography findings underwent routine MR imaging plus 3D contrast-enhanced MR angiography of the spine. Images were reviewed in two stages (stage I, MR images only; stage II, MR images plus MR angiograms) by three neuroradiologists who were blinded to the final diagnoses.
Results: The sensitivity, specificity, and accuracy of the three reviewers in detecting the presence of fistulae ranged from 85% to 90%, from 82% to 100%, and from 87% to 90%, respectively, for stage I, compared with values of 80% to 100%, 82%, and 81% to 94%, respectively, for stage II. For each reviewer, there was no significant difference between the values for stages I and II; however, among the reviewers, one of the more experienced neuroradiologists had significantly greater sensitivity than a less experienced neuroradiologist for stage II. On average, the percentage of true positive results for which the correct fistula level was predicted increased from 15% for stage I to 50% for stage II, and the correct level +/- one level was predicted in 73% for stage II. MR evidence of increased intradural vascularity was significantly greater in patients with dural AVF.
Conclusion: The addition of MR angiography to standard MR imaging of the spine may improve sensitivity in the detection of spinal dural fistulae. The principal benefit of MR angiography is in the improved localization of the vertebral level of the fistula, which potentially expedites the subsequent digital subtraction angiography study.