Spinal dural AV fistula: One stop shop imaging with MR?

Transcription

1 Spinal dural AV fistula: One stop shop imaging with MR? Poster No.: C-3378 Congress: ECR 2010 Type: Educational Exhibit Topic: Neuro Authors: J. C. Röper-Kelmayr 1, C. Ginthör 1, D. Flöry 1, R. Chapot 2, F. A. Keywords: DOI: Fellner 1 ; 1 Linz/AT, 2 Essen/DE spinal dural arterio-venous fistula, magnetic resonance, 3D SPACE, contrast-enhanced MR angiography (MRA) /ecr2010/C-3378 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. Page 1 of 15

2 Learning objectives Knowledge of this rare, but important and typical disorder Knowledge of the clinical findings and importance of early diagnosis Knowledge of the dedicated MR protocol Knowledge of therapeutic options Background Spinal dural arteriovenous fistula (SDAVF) is a rare, slowly progressive disorder. According to the classification scheme of Anson and Spetzler four subtypes are described [1]: Type I represents dural arteriovenous fistula (AVF), with single (IA) or multiple (IB) feeding arteries. Type II describes the intramedullary, glomus-type arteriovenous malformation (AVM). Type III characterises the juvenile type AVM, consisting of intramedullary, extramedullary and sometimes extradural components. Type IV is the perimedullary fistulous AVM, located intradural extramedullary. Spinal dural arteriovenous fistulas (SDAVF) account for about 70% of all spinal AV shunts. They are usually regarded as acquired lesions, although the exact etiology is not known yet [2]. In contrast to cerebral dural arteriovenous fistulas, where an association with venous sinus thrombosis has been described, it seems to be unlikely that prothrombotic factors are involved in the pathogenesis of spinal dural arteriovenous fistulas [3]. Most of the patients are middle aged men (males:females = 5:1 affected, median age of about 60 years) at the time of diagnosis. The midthoracic region is the most common location of SDAVF [4]. Venous congestion and consecutive increased in spinal venous pressure diminishes the arteriovenous pressure gradient resulting in decreased drainage of normal spinal veins, pathomorphological as progressive myelopathy [2]. Subarachnoid hemorrhage is exceedingly rare in SDAVF [2], although an increased risk of bleeding in cervical SDAVF has been reported, possibly explained by intracranial drainage and venous varix often found in cervical SDAVF [5]. Page 2 of 15

3 Initial symptoms are often low back pain, late symptoms may be neurological deficits such as paraesthesia, paralysis, ataxia, disorder of urinary bladder or the rectum. Without treatment, SDAVF will result in irreversible paralysis. It is well-known, that diagnosis is delayed in the case of SDAVF. Imaging findings OR Procedure details The diagnostic method of choice is dedicated MRI in combination with MRA of the complete spine. Standard MR imaging includes the acquisition of T2-weighted and T1- weighted (before and after i.v. gadolinium administration) (turbo) spin-echo sequences in the sagittal and transverse orientation. Findings include the typical aspect of dilated pial veins, best seen on T2-weighted images. Venous congestion leads to hyperintense signal alterations of the - often thickened - spinal cord, with consecutive contrast enhancement after i.v.-administration of gadolinium. Improved visualization of the dilated pial veins can be achieved with the additional acquisition of T2-weighted 3D sequences, for example 3D turbo spin-echo, 3D SPACE (3D turbo spin-echo with stimulated echoes), 3D CISS (gradient-echo). 3D SPACE sequences may be a promising technique in further evaluation, especially in defining the level of the fistula. SPACE - Sampling Perfection with Application optimized Contrasts using different flipangle Evolution - is a variant of the 3D turbo Spin-Echo (TSE) technique. SPACE allows the acquisition of high-contrast 3D data sets with T1-, T2- or T2-contrast with dark CSF (FLAIR) in acceptable measurement times. 2-5 Based on a 3D turbo spin-echo (TSE) sequence with a long echo train and different flip angles of the refocussing pulses SPACE produces regular as well as stimulated spin-echo. Adding an inversion pulse at the beginning of the sequence T1 contrast or FLAIR contrast can be generated. Similar to a CISS sequence T2-weighted SPACE can be used to identify the dilated pial veins (Fig. 1). Moreover, the fistula may be visualized by means of multiplanar reformations of the isotropic thin-slice images (Fig. 2,3). High resolution contrast-enhanced MRA is also able to locate the fistula which is helpful for following interventional procedures (Fig. 4,5). The latter requires detailed evaluation of the MRA source images using multiplanar reformations. Contrast-enhanced 3D MRA can indeed achieve an improved spatial resolution, but at the cost of temporal resolution. So it can be tricky to pinpoint the exact point of transition from arteries to veins as it may occur that by the time scan is completed, most of the first pass contrast is in the veins [6]. In the case of surgical therapy, diagnostic catheter angiography following the MR examination is indicated yet. Page 3 of 15

4 Targeted volume rendering is a very valuable adjunct in these cases (Fig. 6). Visualizing the fistula with conventional catheter angiography is known as a challenging and difficult task, with well-known pitfalls and possible complications. Therapeutic options for spinal dural arterio-venous fistulas are surgical or interventional therapy. Images for this section: Page 4 of 15

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6 Fig. 1: T2-weighted 3D SPACE showing dilated pial veins surrounding the spinal cord as well as venous congestion edema with hyperintense signal in the thoracic cord. Fig. 2: Visualization of the spinal dural arterio-venous fistula (arrows) with 3D SPACE (slice thickness = 1 mm). Enlarged focussed image from the same data set as in Fig. 2. Page 6 of 15

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8 Fig. 3: Transverse reconstruction from the SPACE data set showing the fistula within the left-sided neuroforamen (arrows). Fig. 4: Contrast-enhanced MR angiogram showing the fistula (arrows). Please compare with the SPACE sequence (Fig. 2). Page 8 of 15

9 Fig. 5: Transverse reconstruction from the 3D contrast-enhanced MR angiogram showing the fistula within the left-sided neuroforamen (arrows). Please compare with the SPACE sequence (Fig. 3). Page 9 of 15

10 Fig. 6: Targeted volume rendering of the contrast-enhanced 3D MR angiogram providing an impressing three-dimensional visulization of the fistula (arrows). Page 10 of 15

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12 Fig. 7: Interventional therapy of the fistula (Rene Chapot, Essen): preinterventional image. Page 12 of 15

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14 Fig. 8: Interventional therapy of the fistula (Rene Chapot, Essen): postinterventional image. Page 14 of 15

15 Conclusion Therefore, MRI and MRA as non-invasive diagnostic methods are of enormous value in cases with SDAVF. The task for x-ray angiography in the meantime is interventional therapy of these lesions (Fig. 7,8). Personal Information References [1] Anson JA, Spetzler RF. Classification of spinal arteriovenous malformations and implications for treatment. BNI Qtr 1992;8:2-8 [2] Krings T, Mull M, Gilsbach JM, Thron A. Spinal vascular malformations. Eur Radiol 2005; 15: [3] Jellema K, Tijssen CC, Fijnheer R, de Groot PG, Koudstaal PJ, van Gijn J. Spinal dural arteriovenous fistulas are not associated with prothrombotic factors. Stroke 2004; 35: [4] Jellema K, Canta LR, Tijssen CC, van Rooij WJ, Koudstaal PJ, van Gijn J. Spinal dural arteriovenous fistulas: clinical features in 80 patients. J Neurol Neurosurg Psychiatry 2003;74: [5] Aviv RI, Shad A, Tomlinson G, Niemann D, Teddy PJ, Molyneux AJ, Byrne JV. Cervical dural arteriovenous fistulae manifesting as subarachnoid hemorrhage: report of two cases and literature review. AJNR Am J Neuroradiol 2004;25: [6] Sharma AK, Westesson PL. Preoperative evalution of spinal vascular malformation by MR angiography: how reliable is the technique: case report and review of literature. Clin Neurol Neurosurg 2008;110: Page 15 of 15