Spinal dural arteriovenous fistulas and intrathecal venous drainage: correlation between digital subtraction angiography, magnetic resonance imaging, and clinical findings

Clinical article

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Object

Spinal dural arteriovenous fistulas (SDAVFs) cause myelopathy through arterialization of the perimedullary venous plexus and venous congestion of the spinal cord. The authors hypothesized that the craniocaudal extent of engorgement of intrathecal draining veins between the fistula site and the point of drainage out of the thecal sac correlates with the degree of myelopathy.

Methods

A retrospective review of the authors' institution's radiology databases identified 31 patients with SDAVFs who had undergone digital subtraction angiography (DSA) and MRI examinations of the spine. The authors counted the number of vertebral body levels of spinal cord enhancement and intrathecal vessel enhancement on T1-weighted postcontrast MRI studies. They also counted the number of levels of cord hyperintensity and intrathecal flow voids on T2-weighted MRI studies. On DSA, the authors identified the number of vertebral body levels of dilated intrathecal draining veins and outflow points from intrathecal veins to epidural veins. Functional status of the patients at the time of diagnosis was assessed using the Aminoff-Logue scale (ALS).

Results

Enlargement of the intrathecal draining veins averaged 10 ± 7.7 spinal levels on DSA. Patients with enlarged draining veins extending 10 or more spinal levels on DSA had worse ALS scores (mean gait 3.4, mean micturition 1.5) than patients with draining veins extending fewer than 10 levels (mean gait 1.8, mean micturition 0.6; p = 0.009 and 0.02, respectively). The number of vertebral body levels of enlarged draining veins correlated with the ALS score (gait r = 0.42, p = 0.009; and micturition r = 0.55, p = 0.0006). More extensive enlarged draining veins were associated with more spinal cord T2 hyperintensity, T2 intrathecal flow voids, and T1 vessel enhancement but not cord enhancement.

Conclusions

The craniocaudal extent of enlarged intrathecal veins draining SDAVF correlates with patient functional status, providing further insight into the pathophysiology of venous hypertensive myelopathy.

Abbreviations used in this paper:ALS = Aminoff-Logue scale; AMV = anterior midline spinal vein; DAVF = dural arteriovenous fistula; DSA = digital subtraction angiography; PMV = posterior midline spinal vein; SDAVF = spinal dural arteriovenous fistula.

Article Information

Address correspondence to: Steven W. Hetts, M.D., Department of Neurointerventional Radiology, 505 Parnassus Avenue, L-352, San Francisco, California 94143-0628. email: steven.hetts@ucsf.edu.

Please include this information when citing this paper: published online February 10, 2012; DOI: 10.3171/2012.1.SPINE11643.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Craniocaudal extent of dilated intrathecal draining veins on DSA in 31 patients with SDAVF. The total number of spinal levels of dilated venous drainage (x axis) is plotted against the number of patients (y axis) who had a given draining vein length. Most patients in this cohort had dilated intrathecal draining veins extending fewer than 10 spinal levels.

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    Case 1. Magnetic resonance imaging characteristics of SDAVF intrathecal veins in a 35-year-old man with several weeks of urinary hesitancy and 1 day of acute paraparesis. A: Sagittal T2-weighted fast spin echo image of the lower thoracic spine demonstrating enlarged intrathecal flow voids dorsal and ventral to the spinal cord extending over 17 spinal levels (full extent not shown). The spinal cord itself demonstrates abnormal T2 hyperintensity over 8 spinal levels. B: Contemporaneous postcontrast T1-weighted fat saturated sagittal image revealing enhancement of the enlarged vessels dorsal and ventral to the spinal cord over 10 spinal levels. C and D: Axial T2-weighted fast spin echo images at T-10 (C) and T-9 (D) confirming an abnormally enlarged vessel along the anterior midline spinal cord, as well as a collection of enlarged vessels posterolateral to the spinal cord on the right. The T2 hyperintensity of the central spinal cord with relative T2 hypointensity of the surface of the spinal cord is compatible with venous congestion.

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    Case 1. Digital subtraction angiography characteristics of SDAVF intrathecal veins. A: Sequential images from selective catheter injection of the right T-11 intercostal artery revealing an SDAVF in the right T-11 neural foramen that initially drains cranially to the enlarged PMV (pmv), which, as seen in the second panel, sends branches both cranially and caudally along the back of the spinal cord. By the fourth panel, the AMV (amv) is seen coursing cranially. B: Sequential images from selective catheter injection of the right T-11 intercostal artery centered at the conus demonstrating that the caudally coursing PMV anastomoses with the AMV, thus providing the route for eventual filling of the AMV. Additionally, a right cauda equina radiculomedullary vein courses caudally from just above the conus and pierces the dura to decompress into extrathecal veins (arrowhead, panel 3). C: Sequential images from selective catheter injection of the right T-11 intercostal artery (with the carina at the top of the first 4 panels and with the carina in the bottom third of panels 5 and 6) demonstrating eventual transdural decompression of the cranially coursing intrathecal veins on the right at C-5 (arrowhead, panel 5) and on the left at T-1 (arrowhead, panel 6). Overall, 21 spinal levels of dilated intrathecal draining veins were identified, including 14 levels above the fistula site and 7 levels below the fistula site. D and E: Axial CT reconstructions obtained during selective catheter injection of the right T-11 intercostal artery demonstrate the fistula site just inside the right neural foramen at T-11 (D), as well as the abnormally enlarged PMV and AMV; at T10 (E), the extreme tortuosity of the PMV as it initially drains cranially from the fistula is well seen.

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    Case 9. Digital subtraction angiograms showing intrathecal venous decompression to extrathecal veins near to and far from the SDAVF fistula site in a 53-year-old man with progressive lower-extremity weakness. An image obtained via a left T-9 intercostal artery injection demonstrating 3 intradural to extradural venous decompression points (arrowheads), including the right T-9 intercostal vein (icv) just contralateral to the fistula site (A), the epidural venous plexus (edv) on the left at T-11 (B), and on the right at L-5 after a long intrathecal venous drainage through a cauda equina vein (B and C, with panel C being a later phase image centered just below the lower margin of panel B).

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