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Spinal MRA: Diagnosis, Pitfalls, and Follow Up Assessment in Patients Treated for Spinal Dural Vascular Malformations 2005

Interventional Spine

Tanmaya C Shah, MD
Rona F Woldenberg , MD, Non ASSR Member
Avi Setton , MD, Non ASSR Member

Purpose

Demonstrate the utility and limitations of contrast enhanced dynamic spinal MR angiography in the diagnosis and long-term assessment of patients successfully treated for spinal dural vascular malformations and secondary pial venous hypertension.

Methods & Materials

Using the protocol designated by Farb et al, MRA was performed on 10 patients in whom a spinal dural vascular malformation was suspected on conventional MR evaluation. An attempt to identify the level of vascular abnormality was undertaken; all patients subsequently underwent spinal catheter angiography. Short-term follow up MRA (within 1 week post-treatment) was obtained in 8 patients. Long term follow up MRA (4-6 months post-treatment) was correlated with spinal catheter angiography.

Results

All 10 patients demonstrated dilated venous structures on the surface of the spinal cord, consistent with venous hypertension associated with a spinal dural vascular malformation. Correlation with spinal catheter angiography revealed that, of the 10 patients with a suspected dural fistula, spinal MRA correctly identified the anatomic location of the fistula in 8 patients. Pitfalls encountered in the interpretation of MRA findings included: 1) lack of fistula recognition secondary to incomplete coverage of the spinal dural surface, specifically the lower lumbar area, during initial MRA examination; 2) misidentification of a dominant anterior spinal artery as a draining medullary vein; 3) the erroneous conclusion that an outlet vein actually represented the level of the fistula. Angiography revealed two patients with an epidural arteriovenous fistula rather than a simple dural fistula, one of which was correctly identified on the initial diagnostic MRA. The immediate post-treatment MRA and the long-term follow up MRA demonstrated significantly reduced vascularity and myelopathy that correlated with clinical improvement and findings at follow up catheter angiography.

Conclusion

Dynamic contrast enhanced spinal MR angiography is a valuable and accurate modality in the diagnosis and pre-treatment evaluation of patients with spinal dural fistulas. The information retrieved from pre-procedure MRA has allowed for targeted spinal catheter angiography, thus significantly decreasing procedural complexity, duration and contrast load. Based on our findings after correlating MRA with spinal catheter angiography, we are optimistic that spinal MRA will be an effective, reliable, and safe alternative to conventional angiography to monitor long-term success of treatment in patients who undergo obliteration of spinal dural fistulas.

References

1. RI Farb, et al. Spinal Dural Arteriovenous Fistula Localization with a Technique of First-Pass Gadolinium MR Angiography: Initial Experience. Radiology 2002 222: 843-850.
2. BC Bowen, et al. Spinal Dural Arteriovenous Fistulas: Evaluation with MR Angiography. AJNR 1995. Vol 16, Issue 10 2029-2043.