Spinal Dural Arteriovenous Fistula

         The two most common etiologies of back pain and radiculopathy are herniation of the nucleus pulposus and degenerative changes of the spine and neuroforamen1 . Of the myriad causes of nerve compression that lead to radiculopathy, vascular etiologies remain among the most infrequent, with an estimated prevalence of only five to ten per million cases of radiculopathy 2 . In contrast to arteriovenous malformations, which are subdural and more commonly congenital, spinal dural arteriovenous fistulas (SDAVFs) are dural and are often acquired and/or traumatic in origin1,3. SDAVFs present mostly in males (male:female ratio of 5:1) in their fifties and sixties4,5. Clinical symptoms of SDAVF potentially match those of radiculopathy caused by disc herniation—including extremity weakness, numbness, paresthesias, pain, and sphincter dysfunction6,7—and up to 50% of patients with SDAVF have unremarkable findings on magnetic resonance imaging (MRI)2,6. Anatomically, SDAVF is almost exclusively singular, with two distinct fistulae estimated to occur in only 1% to 7% of all cases and more than two fistulae reported only in rare single case reports2,8.

         The identification of vascular malformations that mimic disc herniation is diagnostically challenging, and such cases are therefore presumably underreported in the literature. Since the original description of SDAVFs in 19779,10, only two authors have described them in the orthopaedic spine literature. Furthermore, to our knowledge, no single report has comprehensively described the clinical presentation, imaging, operative findings, and treatment of SDAVF. In this case report, we outline the clinical presentation, imaging, intraoperative findings, and postoperative course for a patient with an intradural, extramedullary SDAVF at the L1-L2 level who presented only with axial back pain and unilateral lower-extremity radiculopathy. Methods to identify this rare entity as well as the potential risk of a missed diagnosis are described for the spine community. The patient was informed that information regarding the case would be submitted for publication, and he consented. Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work.

         No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article. 1 COPYRIGHT 2015 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED JBJS Case Connect 2015;5:e59 d http://dx.doi.org/10.2106/JBJS.CC.M.00284 Case Report Presentation Afifty-four-year-old man presented to our office with chronic low back pain and new-onset left lower-extremity radiculopathy radiating from the buttock to the anterior proximal part of the thigh (L2 distribution). His symptoms were exacerbated with activity and sitting but were alleviated with rest and by lying supine. There were no motor deficits or symptoms involving the bowels or bladder on presentation. The patient’s medical history was remarkable for mild scoliosis, kidney disease, and a thyroid disorder. His surgical history was negative for any spinal surgery or trauma, and the patient indicated that he did not use alcohol or tobacco. On physical examination, the patient appeared well, was afebrile, and had stable vital signs.

         Musculoskeletal examination revealed spinal extension that was limited to 75% of normal. Neurological examination revealed full strength in both lower extremities, with the exception of grade-4 (of 5) strength with flexion of the left hip. Reflexes and sensation to light touch were intact. The patient exhibited no gait abnormalities. Imaging MRI performed one month prior to the examination revealed what initially appeared to be a large disc extrusion at the L1-L2 level causing severe neural foraminal narrowing and compression of the left L2 nerve root as well as a moderate disc herniation at the L2-L3 level. However, after further review with the spine Fig. 1-A Fig. 1-B Fig. 1-C Fig. 1-D Figs. 1-A through 1-D T2-weighted MRI of the spine one month prior to the initial operation. Fig. 1-A Sagittal view demonstrating evidence of a large disc extrusion at L1-L2 (versus disc extrusion with facet hypertrophy) as well as additional disc herniations at L2-L3 and moderate to severe spinal stenosis at L4-L5 with multilevel degenerative disc disease and collapse. Figs. 1-B, 1-C, and 1-D Axial views at the level of the L1-L2 disc space demonstrating disc extrusion (versus disc extrusion with facet hypertrophy) causing severe neuroforaminal narrowing of the lateral recess. 2 JBJS CASE CONNECTOR VOLUME 5 d NUMBER 3 d JULY 8, 2015 SPINAL DURAL ARTERIOVENOUS FISTULA PRESENTING AS A RECURRENT NUCLEUS PULPOSUS HERNIATION and radiology teams, it was determined that the neural foraminal compression could be caused by a disc extrusion with coexisting facet joint hypertrophy.

         The MRI also revealed moderate to severe spinal stenosis at the L4-L5 level, with multilevel degenerative disc disease (Figs. 1-A through 1-D). RepeatMRI demonstrated disc desiccation with symmetrical disc bulging at the L1-L2 disc space. Additionally, there was an epidural rim enhancement on T2 imaging, which was presumed to be an extruded free disc fragment (Figs. 2-A, 2-B, and 2-C). Operative Findings The patient elected to undergo a left-sided L1-L2 neuroforaminal decompression and partial discectomy. A 3-mm Kerrison rongeur was used to perform a laminectomy at L1 and L2. Lateral recess decompression was performed bilaterally at L1-L2 using a 2-mm Kerrison rongeur, removing the ligamentum flavum and performing a partial medial facetectomy. While performing a midline L1-L2 discectomy, a disc extrusion was noted but this was not a large herniation. Brisk and persistent bleeding was encountered on decompressing the lateral recess and neuroforamen; this required extensive electrocautery in addition to Gelfoam sponge (Upjohn) and FloSeal (Baxter) to achieve hemostasis.

         The discectomy ultimately resulted in total blood loss of 2 L. Tissue for biopsy was sent for pathologic examination; however, the material was collected from the midline disc extrusion and ligamentum flavum prior to decompressing the lateral recess and encountering the substantial bleeding. The biopsy specimen was determined to be benign fibrous tissue, consistent with a vertebral disc. The patient’s initial postoperative course was uneventful. However, ten weeks after the discectomy, he returned for followup evaluation reporting recurrent low back pain (7 on a scale of 0 to 10) with left-sided radiculopathy. MRI with contrast at this time again demonstrated a lobular focus of low signal on T1 and T2-weighted images at L1-L2 extending into the neuroforamen, similar to prior imaging studies (Figs. 3-A, 3-B, and 3-C). The radiology report suggested a new disc extrusion accompanied by a complex synovial cyst (versus pigmented villonodular synovitis).

         However, because of the persistent bleeding encountered during the initial discectomy, there was concern for a vascular etiology. Therefore, the neurosurgical team performed a transfemoral spinal angiogram with selective right L1 and L2 segmental artery catheterization. Multiple imaging runs showed an SDAVF with early venous drainage and multiple small racemic feeders. Additionally, the right L2 segmental artery demonstrated multiple feeders through the SDAVF (Figs. 4-A and 4-B). A revision Fig. 2-A Fig. 2-B Fig. 2-C Figs. 2-A, 2-B, and 2-C Preoperative T2-weighted axial MRIs of the spine at the level of the L1-L2 disc space demonstrating disc desiccation with symmetrical disc bulging obliterating the left lateral recess and causing impingement of the left traversing nerve. Additionally, there is an epidural rim enhancement presumed to be an extruded free disc fragment. This compression may also have been related to disc extrusion with facet joint hypertrophy. 3 JBJS CASE CONNECTOR VOLUME 5 d NUMBER 3 d JULY 8, 2015 SPINAL DURAL ARTERIOVENOUS FISTULA PRESENTING AS A RECURRENT NUCLEUS PULPOSUS HERNIATION Fig. 3-A Fig. 3-B Fig. 3-C Figs. 3-A, 3-B, and 3-C T2-weighted axial MRI of the spine at the level of the L1-L2 disc space three months after the L1-L2 discectomy, again demonstrating a lobular focus of low signal extending into the foramen impinging on the left exiting L1 nerve, similar to prior imaging studies.

         This was initially thought to be a new disc extrusion accompanied by a complex synovial cyst containing blood products (versus potential pigmented villonodular synovitis). Further diagnostic testing would reveal this to be an SDAVF at the level of the L1 and L2 vertebrae with multiple feeder vessels. Fig. 4-A Fig. 4-B Figs. 4-A and 4-B Intraoperative angiograms. Fig. 4-A Left L1 segmental artery injection showing a racemic arteriovenous fistula with an early draining vein going cephalad. Fig. 4-B Left L2 segmental artery injection showing the arteriovenous fistula and the dilated vein. 4 JBJS CASE CONNECTOR VOLUME 5 d NUMBER 3 d JULY 8, 2015 SPINAL DURAL ARTERIOVENOUS FISTULA PRESENTING AS A RECURRENT NUCLEUS PULPOSUS HERNIATION decompression was performed with bilateral L1 and L2 laminectomy as well as microsurgical resection of the SDAVF with durotomy and cauterization. The postoperative course was uneventful. Follow-up At one year after presentation, the patient had made a full recovery.

         He had returned to work full time as a manual laborer, with no recurrence of the axial back pain or lumbar radiculopathy. Neurological examination revealed grade-5 strength in all distributions in both lower extremities, with no residual sensory deficits. Discussion The exact etiology of SDAVF is still not fully understood, although it is widely accepted to be an acquired disease1-3,5,11,12 with risk factors that are multifactorial2 . Of the myriad possible triggering events, infection, syringomyelia, trauma, and surgery have been the most commonly observed2,13-16. In 1992, Anson and Spetzler proposed a classification system that divided spinal vascular malformations into four types, with type 1 indicating a dural arteriovenous fistula; type 2, an intramedullary glomus-type arteriovenous malformation; type 3, an intramedullary juveniletype arteriovenous malformation; and type 4, an intradural, extramedullary arteriovenous fistula17. Type-1 SDAVFs are subcategorized into type 1A (single feeding artery) and type 1B (multiple feeding arteries)12. Most SDAVFs are intradural or within the nerve root sleeve. The venous engorgement within the nerve root sleeve traversing the neuroforamen explains the neuropathic symptoms commonly associated with the initial presentation2,4. The most common presenting symptoms reported in association with SDAVF are limb weakness (42.9%), decreased sensation in the lower extremities (20.1%), pain (9.7%), paresthesias (8.5%), and sphincter dysfunction (4.6%)7.

         A mean age of sixty-three years at presentation has been reported, with 78% of patients being male6,7. With this constellation of symptoms mimicking common lumbar spine pathology, there is often a one to two-year delay in appropriate diagnosis, as well as considerable risk for inappropriate and invasive intervention, which occurs in 10 to 22% of cases6,7,18. Wang et al. demonstrated misdiagnosis in >81% of SDAVF cases on initial evaluation, leading to inappropriate and invasive intervention in more than half of those patients19. Review of the literature suggests that T2-weighted MRI of the spine of patients presenting with undiagnosed SDAVF will demonstrate cord signal changes in 73% to 93% of cases6,7,18. According to the classification described above, our patient had a type-1B SDAVF. MRI demonstrated what appeared to be a disc herniation into the neural foramen at the L1-L2 disc space. This led the region of signal intensity in the disc space on T2-weighted MRI to be mistaken for minor hemorrhage associated with a disc injury. In retrospect, the lateral recess stenosis was caused by an SDAVF with coexisting facet hypertrophy.

         With his nonspecific symptoms mimicking more common spine abnormalities, this patient’s diagnosis was a challenge for spine surgeons with both orthopaedic and neurosurgical training. In patients with MRI signal suggestive of vascular malformations (T2 hyperintensity in the lower spinal cord and conus medullaris), MR angiography has a 95% positive predictive value for diagnosing SDAVF7 . Early diagnosis may improve clinical outcomes for these patients and potentially avoid open surgical decompression and the risk of severe hemodynamic complications. Although no substantial vascular abnormality was noted during surgery in the present case, we believe that any patient with profuse, unexplained bleeding intraoperatively should be resuscitated, stabilized, and evaluated with MR angiography. Since many of these patients are being managed in a surgical center or outpatient setting, rapid identification and procurement of blood products may be life-saving. Once appropriately diagnosed, surgical ligation leads to full resolution in up to 97% of patients, with improved or stable motor function7 . Following the microsurgical cauterization of the L1 and L2 fistulae, our patient improved clinically, with decreased foraminal stenosis on radiographic imaging at the two-week follow-up. In addition, at six months and one year of follow-up, the patient remained free of axial back pain or radiculopathy. He returned to work full time as a manual laborer. Patients with persistent symptoms after surgical ligation may warrant additional MR angiography. For these patients, open surgical decompression should be approached with caution.

Kushagra Verma, MD, MS Jacob Fennessy, MD, MS Ronald Huang, MD Department of Orthopaedic Surgery, Thomas Jefferson University, 1025 Walnut Street, Room 516 College, Philadelphia, PA 19107. E-mail address for K. Verma: vermak01@gmail.com Pascal Jabbour, MD Division of Neurovascular Surgery and Endovascular Neurosurgery, Thomas Jefferson University Hospital, 925 Chestnut Street, Philadelphia, PA 19107 Jeffrey Rihn, MD Orthopedic Spine Surgery, The Rothman Institute at Thomas Jefferson University Hospital, 925 Chestnut Street, 5th Floor, Philadelphia, PA 19107 References 1. Benny BV, Nagpal AS, Singh P, Smuck M. Vascular causes of radiculopathy: a literature review. Spine J. 2011 Jan;11(1):73-85. 2. Koch C. Spinal dural arteriovenous fistula. Curr Opin Neurol. 2006 Feb;19(1): 69-75. 5 JBJS CASE CONNECTOR VOLUME 5 d NUMBER 3 d JULY 8, 2015 SPINAL DURAL ARTERIOVENOUS FISTULA PRESENTING AS A RECURRENT NUCLEUS PULPOSUS HERNIATION 3. Rosenblum B, Oldfield EH, Doppman JL, Di Chiro G. Spinal arteriovenous malformations: a comparison of dural arteriovenous fistulas and intradural AVM’s in 81 patients. J Neurosurg. 1987 Dec;67(6):795-802. 4. Marcus J, Schwarz J, Singh IP, Sigounas D, Knopman J, Gobin YP, Patsalides A. Spinal dural arteriovenous fistulas: a review. Curr Atheroscler Rep. 2013 Jul;15(7):335. 5. Rubin MN, Rabinstein AA. Vascular diseases of the spinal cord. Neurol Clin. 2013 Feb;31(1):153-81. 6. Muralidharan R, Saladino A, Lanzino G, Atkinson JL, Rabinstein AA. The clinical and radiological presentation of spinal dural arteriovenous fistula. Spine (Phila Pa 1976). 2011 Dec 1;36(25):E1641-7. 7. Saladino A, Atkinson JL, Rabinstein AA, Piepgras DG, Marsh WR, Krauss WE, Kaufmann TJ, Lanzino G. Surgical treatment of spinal dural arteriovenous fistulae: a consecutive series of 154 patients. Neurosurgery. 2010 Nov;67(5):1350-7; discussion 1357-8. 8. Apostolova M, Nasser S, Kodsi S. A rare case of spinal dural arteriovenous fistula. Neurol Int. 2012 Oct 5;4(3):e19. Epub 2012 Dec 18. 9. Klopper HB, Surdell DL, Thorell WE. Type I spinal dural arteriovenous fistulas: historical review and illustrative case. Neurosurg Focus. 2009 Jan;26(1):E3. 10. Kendall BE, Logue V. Spinal epidural angiomatous malformations draining into intrathecal veins. Neuroradiology. 1977;13:181-9. 11. Borden JA, Wu JK, Shucart WA. A proposed classification for spinal and cranial dural arteriovenous fistulous malformations and implications for treatment. J Neurosurg. 1995 Feb;82(2):166-79. 12. Bowen BC, Fraser K, Kochan JP, Pattany PM, Green BA, Quencer RM. Spinal dural arteriovenous fistulas: evaluation with MR angiography. AJNR Am J Neuroradiol. 1995 Nov-Dec;16(10):2029-43. 13. Asakuno K, Kim P, Kawamoto T, Ogino M. Dural arteriovenous fistula and progressive conus medullaris syndrome as complications of lumbar discectomy. Case report. J Neurosurg. 2002 Oct;97(3)(Suppl):375-9. 14. Finsterer J, Bavinzski G, Ungersb¨ock K. Spinal dural arteriovenous fistula associated with syringomyelia. J Neuroradiol. 2000 Sep;27(3):211-4. 15. Flannery T, Tan MH, Flynn P, Choudhari KA. Delayed post-surgical development of dural arteriovenous fistula after cervical meningocele repair. Neurol India. 2003 Sep;51(3):390-1. 16. Vankan Y, Demaerel P, Heye S, Van Calenbergh F, van Loon J, Maleux G, Wilms G. Dural arteriovenous fistula as a late complication of upper cervical spine fracture. Case report. J Neurosurg. 2004 Apr;100(4)(Suppl Spine):382-4. 17. Anson JA, Spetzler RF. Interventional neuroradiology for spinal pathology. Clin Neurosurg. 1992;39:388-417. 18. Narvid J, Hetts SW, Larsen D, Neuhaus J, Singh TP, McSwain H, Lawton MT, Dowd CF, Higashida RT, Halbach VV. Spinal dural arteriovenous fistulae: clinical features and long-term results. Neurosurgery. 2008 Jan;62(1):159-66; discussion 166-7. 19. Wang D, Yang N, Zhang P, Xu S, Li X, Zhao P, Huang B. The diagnosis of spinal dural arteriovenous fistulas. Spine (Phila Pa 1986). 2013 Apr 20;38(9): E546-53.

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