Localization of sacral spinal arteriovenous fistulae in reference to the dural structure with CTA and MRA of high spatial resolution: A pictorial essay Poster No.: C-2581 Congress: ECR 2010 Type: Educational Exhibit Topic: Neuro Authors: S. Inagawa, N. Yoshimura, Y. Ito; Niigata/JP Keywords: spinal sacral areteriovenous fistulae, CTA, MRA DOI: 10.1594/ecr2010/C-2581 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 13
Learning objectives To learn the usefulness of CT angiography (CTA) with multidetector CT (MDCT) and MRI of high spatial resolution in three-dimensionally locating a shunting segment of sacral spinal arteriovenous fistulas (AVFs) in reference to the dural structures such as the dural sac and the root sleeves. Background Conventional catheter angiography is the gold standard in the diagnosis of spinal AVFs, but is not capable to visualize the dural structures and thus has left us to our own virtuosity when we locate a shunting point in reference to the dural structures, which is crucial for precise diagnosis and appropriate treatment but sometimes difficult especially in the sacral region. Here we present two cases of sacral AVFs in which it was not clear if they were epidural or dural AVF solely on angiograms as you see in Fig 1, 2, and CTA and MRI of high spatial resolution helped a lot in the differential diagnosis as well as in planning a treatment strategy. Intraoperative findings are presented with photos. Images for this section: Page 2 of 13
Fig. 1: Case 1 Lt internal iliac angiogram. Page 3 of 13
Fig. 2: Case 2 Lt internal iliac angiogram Page 4 of 13
Imaging findings OR Procedure details Case 1; a man in his 50's presenting with gradual progression of sensorimotor deficits in the bilateral lower extremities. The shunting segment, the target of therapeutic intervention whatever modality should be taken, is clearly depicted in angiography as shown in Fig. 1 with circles. But where is it in reference to the dural structures? Is this dural or epidural? Heavily T2-wighted MRI (Fig. 2) detects that the enlarged draining vein (arrows) joins the end of the cul de sac of dura (arrow heads), which means that it is the vein of the filum terminale. Now that we know the draining vein is the vein of the filum terminale, where is the shunting segment located in reference to the dura? Is it intradural, epidural, or extradural? CTA (Fig. 3) depicts the enlarged vein of the filum terminale and its continuation below the end of the dural sac (circle), which corresponds the shunting segment (circle) on the angiogram. This means that the shuntig segment lies at the end of the dural sac or its dural continuation below. The feeders were too fine to be visualized in CTA. During surgery (Fig. 4), the intradural enlarged vein (arrows) was found to join the end of the dural sac, on the external surface of which some possible feeders (dotted arrow) were noticed. Coagulated and severed, the enlarged vein was lifted up, along which the filum terminale (arrow head) was found to lie side by side. The final diagnosis is a dural AVF at the end of the dural sac. As we see above, CTA and MRI helped us much in locating the shunting segment in reference to the dural structure, i.e. in the differnetial diagnosis. Case 2; a woman in her 70's presenting with gradual progression of paraparesis. The shunting segment, the target of therapeutic intervention whatever modality should be taken, is clearly depicted in angiography as shown with circles in Fig. 5. But where is it in reference to the dural structures? Is this dural or epidural? Sagittal source images of contrast enhanced (CE ) MR angiography (MRA) depicts that the enlarged draining vein (arrows) runs in zigzag in the extradural fat of hyperintensity and then penetrates the dura to ascend in the intradural space of hypointensity (Fig. 6). CTA (Fig. 7) also shows that the draining vein (arrows) runs from the extradural space of hypodensity into the intradural space of isodensity and that the shunting point (arrow head) lies in the extradural space anteromedial to the left S1 root sleeve. The feeder was too fine to be clearly visualized in CTA. Page 5 of 13
During the surgery, coagulation and cutting of the intradural draining vein still left a residual flow through the epidural AVF visalized in intraoperative DSA. Exploration revealed an arterialized epidural venous plexus (circle in Fig. 8) in the left anterior epidural space at the level of S1 root sleeve (arrow). Coagulation of the venous plexus led to complete occlusion of the AVF. The final diagnosis is an epidural AVF in the anterior epidural space in front of the left S1 root sleeve. CTA and MRI helped us in locating the shunting point in reference to the dural structure. Discussion; It has been well reported that CTA or MRA helps in search for feeders of spinal dural AVF [1,2], but their potential to differentiate between dural or epidural AVF, as demonstrated here in this presentation, has not yet been emphasized. It is accentuated in the sacral region, where the root sleeves closer to the midline than in the thoracolumbar or cervical region project themselves over the epidural venous plexus in the AP view of DSA, making it difficult to differentiate between dural and epidural AVFs in the sacral region with angiography alone. Images for this section: Page 6 of 13
Fig. 1: Case1 Right (on your left: arterial phase) and left internal iliac angiograms, AP view (middle:late arterial phase, on your right: arterial phase).the circle indicates the shunting segment. Page 7 of 13
Fig. 2: Case 1 Heavily T-wighted MRI in coronal section. The enlarged vein (arrows) joins the end of the cul de sac of dura(arrow heads), which means that it is the vein of the filum terminale. Fig. 3: Case 1 CTA (two images on the left) depicts the enlarged vein of the filum terminale and its continuation below the end of the dural sac (circle), which corresponds the shunting segment (circle) on the angiogram(two images on the right). Red fragmented lines on CTA indicate the dural cover. This means that the shuntig segment lies at the end of the dural sac or its dural continuation below. The feeders were too fine to be visualized in CTA. Fig. 4: Case 1 During surgery, the intradural enlarged vein (arrows) was found to join the end of the dural sac (its level is indicated with the fragemented line), on the external surface of which some possible feeders (dotted arrow) were noticed. Coagulated and Page 8 of 13
severed, the enlarged vein was lifted up, along which the filum terminale (arrow head) was found to lie side by side. Fig. 5: Case 2 Left internal iliac angiograms:from left to righ, late arterial phase (most left) and arterial phase (second left) in laetral view, late arterial phase (second right) and arterial phase (most right) in AP view. The shunting segment, the target of therapeutic intervention whatever modality should be taken, is clearly depicted as indicated with circles. Page 9 of 13
Fig. 6: Case 2 Sagittal source images of contrast enhanced (CE ) MR angiography (MRA) with left iliac angiograms in lateral view as reference. Fragmented red lines indicate the dural cover. CE MRA depicts that the enlarged draining vein (arrows) runs in zigzag in the extradural fat of hyperintensity and then penetrates the dura to ascend in the intradural space of hypointensity. Page 10 of 13
Fig. 7: Case 2 CTA and left iliac angiograms in laetral view. On the right at bottom is an angiogram with microcatheter injection. Red fragmented lines indicate the dural cover, and the red arrow the left S1 root sleeve. CTA also depicts that the draining vein (arrows) runs from the extradural space of hypodensity into the intradural space of isodensity and that the shunting point (arrow head) lies in the extradural space anteromedial to the left S1 root sleeve. The feeder was too fine to be clearly visualized in CTA. Page 11 of 13
Fig. 8: Case 2 During the surgery, coagulation and cutting of the intradural draining vein still left a residual flow through the epidural AVF visalized in intraoperative DSA. Exploration revealed an arterialized epidural venous plexus (circle) in the left anterior epidural space at the level of S1 root sleeve (arrow). Coagulation of the venous plexus led to complete occlusion of the AVF. Page 12 of 13
Conclusion Contrast enhanced CTA and MRI or MRA of high spatial resolution are sometimes useful in locating the shunting segment of sacral spinal AVFs in reference to the dural structures for differential diagnosis between dural and epidural AVFs and for better treatment planning as well. Personal Information Shoichi Inagawa1, Norihiko Yoshimura 1, Yasushi Ito2 Department of Radiology, Niigata University Medical and Dental Hospital1, and Department of Neurosurgery, Niigata University Brain Research Institute2, Niigata, Japan References 1. Lai PH, Weng MJ, Lee KW, Pan HB. Multidetector CT angiography in diagnosing type I and type IVA spinal vascular malformations. AJNR Am J Neuroradiol. 2006 Apr;27(4):813-7 2. Luetmer PH, Lane JI, Gilbertson JR, et al. Preangiographic evaluation of spinal dural arteriovenous fistulas with elliptic centric contrast-enhanced MR angiography and effect on radiation dose and volume of iodinated contrast material. AJNR Am J Neuroradiol 2005;26:711-18 Page 13 of 13