Open surgical ligation of a thoracic spinal epidural arteriovenous fistula causing thoracic myelopathy: illustrative case

Brandon R. W. Laing Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin

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Benjamin Best Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin

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John D. Nerva Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin

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Aditya Vedantam Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin

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BACKGROUND

Spinal epidural arteriovenous fistulas (eAVFs) are rare spinal vascular malformations characterized by an abnormal connection from the paraspinal and paravertebral system to the epidural venous plexus. This contrasts with the more frequently seen spinal dural AVF, where the fistula is entirely intradural. Although endovascular repair is commonly performed for spinal eAVF, few cases require open surgical ligation.

OBSERVATIONS

The authors present a case of a 74-year-old male with progressive thoracic myelopathy secondary to a spinal eAVF. Thoracic magnetic resonance imaging (MRI) showed intramedullary T2 signal hyperintensity from T8 to T12. Spinal angiography revealed a primary arterial supply from the right T11 segmental artery and minor supply from the left T11 branches with drainage into the ventral epidural space. The patient underwent T11–12 laminectomy and complete right T11–12 facetectomy for ligation of the fistula with T11–L1 fusion. A postoperative spinal angiogram showed resolution of the fistula. Postoperatively, the patient’s myelopathy improved, and MRI showed a decrease in T2 cord intensity.

LESSONS

Spinal eAVFs are rare lesions that differ from the more commonly seen intradural dural AVF in that the abnormal connection is in the epidural space, and they are often associated with a dilated epidural venous pouch. Treatment involves endovascular, open surgical, or combined approaches.

ABBREVIATIONS

ASA = anterior spinal artery; AVF = arteriovenous fistula; DAVF = dural arteriovenous fistula; eAVF = epidural arteriovenous fistula; MRI = magnetic resonance imaging

BACKGROUND

Spinal epidural arteriovenous fistulas (eAVFs) are rare spinal vascular malformations characterized by an abnormal connection from the paraspinal and paravertebral system to the epidural venous plexus. This contrasts with the more frequently seen spinal dural AVF, where the fistula is entirely intradural. Although endovascular repair is commonly performed for spinal eAVF, few cases require open surgical ligation.

OBSERVATIONS

The authors present a case of a 74-year-old male with progressive thoracic myelopathy secondary to a spinal eAVF. Thoracic magnetic resonance imaging (MRI) showed intramedullary T2 signal hyperintensity from T8 to T12. Spinal angiography revealed a primary arterial supply from the right T11 segmental artery and minor supply from the left T11 branches with drainage into the ventral epidural space. The patient underwent T11–12 laminectomy and complete right T11–12 facetectomy for ligation of the fistula with T11–L1 fusion. A postoperative spinal angiogram showed resolution of the fistula. Postoperatively, the patient’s myelopathy improved, and MRI showed a decrease in T2 cord intensity.

LESSONS

Spinal eAVFs are rare lesions that differ from the more commonly seen intradural dural AVF in that the abnormal connection is in the epidural space, and they are often associated with a dilated epidural venous pouch. Treatment involves endovascular, open surgical, or combined approaches.

ABBREVIATIONS

ASA = anterior spinal artery; AVF = arteriovenous fistula; DAVF = dural arteriovenous fistula; eAVF = epidural arteriovenous fistula; MRI = magnetic resonance imaging

Spinal epidural arteriovenous fistulas (eAVFs) are rare vascular lesions that occur because of the development of a fistulous connection between the paraspinal/paravertebral arteries and the epidural venous plexus.1 Similar to the more commonly seen spinal intradural AVFs, these lesions can cause symptoms of congestive myelopathy, thought to be secondary to the significant venous hypertension that results from the abnormal arteriovenous connection. The purpose of this article is to illustrate the surgical treatment of a rare type of spinal AVF and demonstrate technical pearls for successful open ligation of these lesions. Endovascular embolization of spinal eAVF has been described; however, in the present report, we describe a rare case of open ligation of a spinal eAVF with an associated surgical video.

Illustrative Case

A 74-year-old male presented with a 1-year history of gait instability and multiple falls. Over the last 3 months prior to presentation, his condition declined rapidly; he required a walker and had urinary and bowel dysfunction.

His physical examination showed symmetric strength (Medical Research Council Scale for Muscle Strength grade 5) in the bilateral upper and lower extremities and intact rectal tone. In addition, he had wide-based unstable gait, a positive Romberg sign, and absent ankle reflexes or clonus. Magnetic resonance imaging (MRI) of the thoracic spine showed T9–10 and T11–12 disc herniation as well as extensive intramedullary hyperintensity from the T8 to T12 vertebral levels (Fig. 1). Given the extensive cord signal change, which was out of proportion to the degree of canal stenosis, a spinal angiogram was obtained because of the suspected vascular etiology. The angiogram showed a ventrolateral eAVF with its major supply from the right T11 segmental artery and minor supply from the left T11 segmental artery with venous drainage into the ventral epidural space (Fig. 2).

FIG. 1.
FIG. 1.

Sagittal (left) and axial (right) T2-weighted MRI of the thoracic spine showing extensive cord signal change spanning the T8 to T12 levels with minimal cord compression.

FIG. 2.
FIG. 2.

Preoperative (left) and postoperative (right) anteroposterior digital subtraction angiograms. White arrow delineates the lateral fistulous connection and epidural venous pouch that is no longer seen on the postoperative projection.

Ligation of the spinal eAVF was indicated, given the extent of T2 signal within the cord and progressive myelopathy, and surgery was offered to the patient. Open surgical ligation was favored over endovascular repair because of the proximity of the anterior spinal artery (ASA) supply and associated risk of reflux of an embolic agent and spinal cord infarction. The main supply to the ASA via the artery of Adamkiewicz originated from the left T10 segmental artery with a minor contribution from the left T11 segmental artery and likely supply from the right T11 segmental artery (Figs. 2, 3).

FIG. 3.
FIG. 3.

Anteroposterior left T10 segmental artery angiogram shows multiple contralateral fistulous connections (white arrow). ASA supply is present and unchanged on preoperative (left) and postoperative (right) imaging. Postoperative angiography confirms successful ligation of the contralateral supply.

The patient underwent T11 and T12 laminectomies and right T11–12 complete facetectomy for fistula ligation with T11–L1 bilateral pedicle screw instrumentation and fusion (Fig. 4 and Video 1). Postoperatively, the patient was admitted to the neurological intensive care unit in stable condition. The patient’s neurological examination revealed that he had full strength in his bilateral lower extremities. He was ultimately discharged home on postoperative day 8 in stable condition. At his 3-month follow-up visit, he was able to ambulate without assistance. His bowel and bladder symptoms had resolved. At the 13-month follow-up, he reported improvement in his preoperative symptoms; however, he had developed left lumbar radicular pain. He underwent MRI of the thoracic and lumbar spine, which showed improvement in the intramedullary signal change in the thoracic spine and multilevel degenerative stenosis throughout his lumbar spine (Fig. 5). The findings of flexion/extension radiographs were negative for dynamic listhesis. Given his symptoms, he underwent electromyography, which showed left-sided L4, L5, and S1 acute polyradiculopathy. He is currently undergoing nonoperative medical management for his lumbar radiculopathy.

VIDEO 1. Clip showing preoperative imaging and explanation. Click here to view.

FIG. 4.
FIG. 4.

Intraoperative findings after the T11–12 laminectomy and right T11–12 facetectomy. Black arrow indicates the lateral epidural venous pouch and fistulous connection with close proximity to the axilla of the right T11 nerve root.

FIG. 5.
FIG. 5.

Sagittal T2-weighted MRI of the thoracic spine preoperatively (left) and postoperatively (right). Images show significant decrease in cord edema change after ligation of the fistula.

Patient Informed Consent

The necessary patient informed consent was obtained in this study.

Discussion

Observations

The present case is a rare example of a spinal eAVF treated with open surgical ligation. In our discussion of the clinical pearls of this case, it is important that we delineate the difference between spinal eAVF and the more commonly seen intradural spinal dural AVFs (dAVFs), as well as the treatment options.

As mentioned previously, spinal eAVFs have anatomical and pathophysiological differences from the more commonly seen spinal dAVFs.2 Anatomically, spinal eAVFs usually develop in the anterior spinal canal or lateral epidural space as an abnormal connection between the paraspinal/paravertebral arteries and an epidural venous pouch.3,4 In the thoracolumbar regions, the arterial supply is usually from the segmental arteries from the aorta, whereas in the cervical region they can be supplied by the thyrocervical trunk and, rarely, the vertebral artery.3 Primary venous drainage is typically through an enlarged epidural venous plexus; however, there have been reported cases of drainage into the azygous system in the thoracic region.3 MRI shows significant T2 cord signal change with possible intradural vascular flow voids and spinal cord enhancement.5 Spinal angiography shows early venous filling of an epidural venous pouch usually located in the ventral epidural space or laterally near the intervertebral foramen.5

Spinal eAVFs can be classified by their venous drainage patterns. First, spinal eAVFs can be classified as type A or B on the basis of their venous drainage.4 Type A spinal eAVFs are associated with intradural venous reflux. Type A eAVFs are usually diagnosed in patients in their sixth decade of life and most commonly occur in the thoracolumbar and lumbar regions.4 In these cases, patients present with myelopathy symptoms thought to be due to venous congestion and high cord signal change on MRI.4 The present case most likely falls into a type A spinal eAVF, given the intradural venous reflux and symptoms of congestive myelopathy. Contrastingly, type B spinal eAVFs do not have intradural venous drainage.3 They often occur in the third decade of life and primarily cause symptoms due to mass effect from the epidural venous pouch, leading to myelopathy or radiculopathy.4,6,7 These lesions more commonly occur in the cervical and upper thoracic regions and may present with hemorrhage.4,7,8

The main goal of treatment for spinal eAVFs is to relieve the cause of the neurological symptoms in the patient. Given that most cases present without mass effect, and given the ventral location of the fistula, much of the literature describes endovascular techniques for treatment. In cases in which there are one or two arterial feeders directly supplying a small epidural venous pouch, endovascular transarterial approaches are favorable, especially in cases of nonosseous spinal eAVFs.9 However, in cases in which there are multiple feeders, transvenous embolization or combined surgical and endovascular techniques may be required.9

Given the rare nature of these lesions and endovascular treatment options, the literature on microsurgical techniques is sparse. In a large multicenter review, Takai et al.10 compared outcomes of microsurgical versus endovascular treatment of spinal eAVFs with venous drainage. In their cohort of 81 patients, microsurgical treatment was performed in 51.8% (n = 42) of the cases. Microsurgery had a lower treatment failure rate (7.5%) than endovascular techniques (31%).10 Surgical ligation had a lower rate of treatment failure, and the most common reason for treatment failure in endovascular cases was multiple arterial feeders.10 In the majority (81%) of patients, microsurgical treatment included ligation of the fistulous connection without disruption of the venous pouch, whereas the other 19% underwent ligation of the venous draining vein with coagulation of the epidural venous plexus.10 In the cases of ligation in which the epidural venous pouch was not coagulated, 75% of patients had spontaneous occlusion of the epidural venous pouch on postoperative angiography.10 Both endovascular and surgical intervention, when radiographically successful, had similar rates of neurological improvement.10

Open surgical ligation was favored over endovascular embolization in this case because of the lateral location of the venous pouch, multiple bilateral arterial feeders, and proximity of supply to the ASA. In the absence of local ASA supply, the small caliber of arterial feeders and numerous connections would have complicated endovascular access and lowered the likelihood of cure with a single procedure, possibly increasing the risk of treatment failure. The lateral location of the fistula, as opposed to a more ventral location, allowed direct surgical exposure via facetectomy, which also permitted access to the ventral arterial feeders supplied from the contralateral T11 segmental artery and to the ventral epidural venous pouch. Because of the wide laminectomy and complete facetectomy adjacent to the thoracolumbar junction, we performed pedicle screw fixation and fusion, given the risk of postoperative spinal instability.

Lessons

Spinal eAVFs differ from spinal dAVFs in that the fistulous connection is in the epidural space and associated with a large venous pouch. They cause symptoms of congestive myelopathy or compressive symptoms due to mass effect from the enlarged epidural venous drainage system. Careful evaluation of the spinal angiogram is necessary to make the diagnosis and identify the arterial feeders and the pattern of venous drainage. Both endovascular and surgical techniques can be used to ligate these fistulas, with the decision based on patient-specific and anatomical considerations. Surgical ligation may have a lower rate of treatment failure and is particularly effective for cases with multiple arterial feeders and difficult endovascular access. In addition, a ventrolateral fistulous connection is accessible via a complete facetectomy, which reduces thecal sac retraction.

Disclosures

Dr. Nerva reported serving as a medical adviser for and is a shareholder in Midwest Interventional Systems LLC and is a shareholder in Synchron LLC, Bendit Technologies Ltd., and Borvo Medical Inc.

Author Contributions

Conception and design: Laing, Nerva, Vedantam. Acquisition of data: Laing, Nerva, Vedantam. Analysis and interpretation of data: Nerva, Vedantam. Drafting the article: Laing, Nerva. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Laing. Administrative/technical/material support: Vedantam. Study supervision: Nerva, Vedantam.

Supplemental Information

Videos

Video 1. https://vimeo.com/836555929.

References

  • 1

    Brinjikji W, Yin R, Nasr DM, Lanzino G. Spinal epidural arteriovenous fistulas. J Neurointerv Surg. 2016;8(12):13051310.

  • 2

    Kim LJ, Spetzler RF. Classification and surgical management of spinal arteriovenous lesions: arteriovenous fistulae and arteriovenous malformations. Neurosurgery. 2006;59(5 suppl 3):S195S201.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Shetty GS, Singh V, Prasad SN, et al. Spinal epidural fistulas—a separate entity to dural fistulas with different angioarchitecture and treatment approach. World Neurosurg. 2021;149:e600e611.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Takai K, Taniguchi M. Comparative analysis of spinal extradural arteriovenous fistulas with or without intradural venous drainage: a systematic literature review. Neurosurg Focus. 2012;32(5):E8.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Nasr DM, Brinjikji W, Clarke MJ, Lanzino G. Clinical presentation and treatment outcomes of spinal epidural arteriovenous fistulas. J Neurosurg Spine. 2017;26(5):613620.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Song Y, Cho SH, Lee DW, Sheen JJ, Shin JH, Suh DC. Osseous versus nonosseous spinal epidural arteriovenous fistulas: experiences of 13 patients. AJNR Am J Neuroradiol. 2019;40(1):129134.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Asai J, Hayashi T, Fujimoto T, Suzuki R. Exclusively epidural arteriovenous fistula in the cervical spine with spinal cord symptoms: case report. Neurosurgery. 2001;48(6):13721376.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Kāhārā V, Lehto U, Ryymin P, Helén P. Vertebral epidural arteriovenous fistula and radicular pain in neurofibromatosis type I. Acta Neurochir (Wien). 2002;144(5):493496.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Al-Abdulwahhab AH, Song Y, Kwon B, Suh DC. Embolization tactics of spinal epidural arteriovenous fistulas. Neurointervention. 2021;16(3):252259.

  • 10

    Takai K, Endo T, Yasuhara T, et al. Microsurgical versus endovascular treatment of spinal epidural arteriovenous fistulas with intradural venous drainage: a multicenter study of 81 patients. J Neurosurg Spine. 2020;24:111.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • Collapse
  • Expand
  • FIG. 1.

    Sagittal (left) and axial (right) T2-weighted MRI of the thoracic spine showing extensive cord signal change spanning the T8 to T12 levels with minimal cord compression.

  • FIG. 2.

    Preoperative (left) and postoperative (right) anteroposterior digital subtraction angiograms. White arrow delineates the lateral fistulous connection and epidural venous pouch that is no longer seen on the postoperative projection.

  • FIG. 3.

    Anteroposterior left T10 segmental artery angiogram shows multiple contralateral fistulous connections (white arrow). ASA supply is present and unchanged on preoperative (left) and postoperative (right) imaging. Postoperative angiography confirms successful ligation of the contralateral supply.

  • FIG. 4.

    Intraoperative findings after the T11–12 laminectomy and right T11–12 facetectomy. Black arrow indicates the lateral epidural venous pouch and fistulous connection with close proximity to the axilla of the right T11 nerve root.

  • FIG. 5.

    Sagittal T2-weighted MRI of the thoracic spine preoperatively (left) and postoperatively (right). Images show significant decrease in cord edema change after ligation of the fistula.

  • 1

    Brinjikji W, Yin R, Nasr DM, Lanzino G. Spinal epidural arteriovenous fistulas. J Neurointerv Surg. 2016;8(12):13051310.

  • 2

    Kim LJ, Spetzler RF. Classification and surgical management of spinal arteriovenous lesions: arteriovenous fistulae and arteriovenous malformations. Neurosurgery. 2006;59(5 suppl 3):S195S201.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Shetty GS, Singh V, Prasad SN, et al. Spinal epidural fistulas—a separate entity to dural fistulas with different angioarchitecture and treatment approach. World Neurosurg. 2021;149:e600e611.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Takai K, Taniguchi M. Comparative analysis of spinal extradural arteriovenous fistulas with or without intradural venous drainage: a systematic literature review. Neurosurg Focus. 2012;32(5):E8.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Nasr DM, Brinjikji W, Clarke MJ, Lanzino G. Clinical presentation and treatment outcomes of spinal epidural arteriovenous fistulas. J Neurosurg Spine. 2017;26(5):613620.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Song Y, Cho SH, Lee DW, Sheen JJ, Shin JH, Suh DC. Osseous versus nonosseous spinal epidural arteriovenous fistulas: experiences of 13 patients. AJNR Am J Neuroradiol. 2019;40(1):129134.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Asai J, Hayashi T, Fujimoto T, Suzuki R. Exclusively epidural arteriovenous fistula in the cervical spine with spinal cord symptoms: case report. Neurosurgery. 2001;48(6):13721376.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Kāhārā V, Lehto U, Ryymin P, Helén P. Vertebral epidural arteriovenous fistula and radicular pain in neurofibromatosis type I. Acta Neurochir (Wien). 2002;144(5):493496.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Al-Abdulwahhab AH, Song Y, Kwon B, Suh DC. Embolization tactics of spinal epidural arteriovenous fistulas. Neurointervention. 2021;16(3):252259.

  • 10

    Takai K, Endo T, Yasuhara T, et al. Microsurgical versus endovascular treatment of spinal epidural arteriovenous fistulas with intradural venous drainage: a multicenter study of 81 patients. J Neurosurg Spine. 2020;24:111.

    • PubMed
    • Search Google Scholar
    • Export Citation

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