Intradural dorsal arteriovenous fistula: a case report and literature review

Introduction

Background

Intradural dorsal arteriovenous fistula (AVF) is a rare spinal vascular malformation that primarily affects the blood-supplying arteries of the intradural dorsal. Its clinical manifestations are dominated by bilateral lower limb weakness and a lack of specificity in early symptoms, which can easily lead to underdiagnosis or misdiagnosis. Thus, the successful diagnosis of intradural dorsal AVF is difficult.

Rationale and knowledge gap

The lack of specificity of the disease makes it extremely easy to miss or misdiagnose the disease in its early stages.

Objective

This study aims to provide clinical practitioners with diagnostic and therapeutic approaches. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-172/rc).

Case presentation

The patient was a 56-year-old woman who presented to our clinic with lower limb weakness for 3 months. The patient did not have significant bowel, bladder, or sensory deficits. Magnetic resonance imaging (MRI) and contrast-enhanced MRI of the lumbar spine (Figure 1A,1B) reveal abnormal vascular signals within the lumbar spinal canal. Initially, we misdiagnosed this case as an extradural AVF. Subsequent ultrasonographic right internal iliac arteriograms (Figure 1C,1D, with the arrow pointing to the location of the fistulae) revealed AVF in the lumbar spinal canal; the fistulae were located at the L3–4 level, supplied by radiculopathies emanating from the sacral external arteries, and drained through the chondromalacia veins. Ultrasonography of the right internal iliac artery allowed us to diagnose the intradural dorsal AVF. After a clear diagnosis, the patient was treated with surgical resection of the fistula. During the operation (Figure 2A,2B), we found that the fistula was located in the intradural dorsal and was mainly supplied by the upward radicular artery and partially by the downward small radicular artery, which was drained through a soft membranous vein. The operation was uneventful, and the patient’s lower limb weakness improved significantly thereafter. We measured the patient’s lower extremity muscle strength, and both limbs were graded as class V. An MRI performed 2 weeks postoperatively showed that the abnormal vascular shadow in the spinal canal had disappeared (Figure 3A,3B; Figure 4).

Figure 1 Preoperative MRI of the spine. (A,B) Abnormal vascular shadows are seen in the lumbar spinal canal. Spinal angiography. (C,D) Preoperative spinal angiography shows intradural dorsal AVF (arrow) at the L3–L4 level. Blood is supplied by the radicular artery emanating from the lateral sacral artery and drained through the chondral vein. AVF, arteriovenous fistula; MRI, magnetic resonance imaging.

Figure 2 Intraoperative findings. (A) A dilated draining vein (white arrow) is seen on the intradural dorsal (CE) nerve root, and the CE nerve root shows the blood-supplying artery (black arrows) (the longer black arrow indicates the ascending root artery, while the shorter black arrow indicates the descending small root artery). (B) Intraoperative ICG imaging shows complete clamping of the draining vein. CE, cauda equina; ICG, indocyanine green.

Figure 3 Postoperative MRI of the spine. No abnormal vascular shadows are visible on the spinal MRI. (A) MRI plain scan. (B) Gadolinium-enhanced MRI. MRI, magnetic resonance imaging.

Figure 4 Case progress timeline. DSA, digital subtraction angiography.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

Early diagnosis and treatment are crucial for dural dorsal AVFs. However, early-stage dural dorsal AVFs are easily misdiagnosed or overlooked. Compared with similar studies, we achieved earlier diagnosis and successful surgery, with no postoperative complications in the patient. Due to time constraints, longer-term follow-up of the patient was not feasible.

Intradural dorsal AVF is a type of arteriovenous malformation (AVM) occurring below the conus medullaris, which is relatively rare and mostly occurs in middle-aged men (1-5). A review of the existing literature revealed several challenges in the diagnosis and treatment of intradural dorsal AVF. Hong et al. (1) retrospectively reviewed prospectively collected data from two spinal vasculopathy referral centers and compared filum terminale AVF, spinal dural AVF, and intradural dorsal AVF in terms of clinical presentation, imaging, treatment, and prognosis. AVFs within the intradural dorsal are clinically rarer and have a younger age of onset. Tanioka et al. (2) reported a case of intradural dorsal AVF supplied by the proximal radicular artery, which can easily be misinterpreted as a filum terminale AVF on imaging, necessitating multiple confirmations to ensure an accurate diagnosis. Namba et al. (6) pointed out that arterial fistulae are usually supplied by arteries originating from the anterior spinal artery, whereas intradural dorsal AVFs are supplied by more complex arteries, usually involving multiple segmental arteries.

The diagnosis of intradural dorsal AVF relies on imaging, and MRI, magnetic resonance angiography, digital subtraction angiography (DSA), computed tomography angiography, and ultrasound are all helpful modalities, however, among them, DSA remains the optimal choice. MRI, which is low-risk and capable of scanning multiple layers, has become the method of choice for the initial diagnosis, and an abnormal serpentine vascular flow-void image on T1- and T2-weighted images is suggestive of AVF (7-9). Magnetic resonance angiography can provide detailed information about vascular structures and help diagnose AVF (8). DSA is the gold standard for the definitive diagnosis of intradural dorsal AVF, informing further decisions about treatment (10). DSA can show the vascular architecture of the lesion, location of the fistula, and draining vein. A combination of these diagnostic methods can provide an accurate diagnosis of AVF and serve as an important basis for treatment planning.

The goal of intradural dorsal AVF treatment is to completely block the direct arteriovenous shunt, and treatment is mainly surgical or endovascular. Surgical resection of the fistula is the mainstay of treatment. Its importance was emphasized by Shimizu et al. (11) who suggested that surgery may be superior to endovascular embolization in terms of efficacy, and rate of postoperative recurrence. Additionally, due to the long and narrow feeder arteries in the case reported herein, the vascular anatomy favored direct surgery over endovascular treatment. However, surgical treatment carries the risk of trauma as well as possible cerebrospinal fluid leakage, spinal cord infection, and neurologic injury; therefore, individual patients’ situations, including the location and size of the fistula, anatomic characteristics of the supplying and draining veins, and patient’s overall health status should be considered when deciding the treatment option.

Conclusions

Intradural dorsal AVF is a relatively rare disease in clinical practice. Long-term illness may lead to lower limb dysfunction, so its early diagnosis is particularly important. Since DSA serves as the gold standard for its diagnosis, it is necessary to apply DSA for examination in the early stage.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-172/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-172/prf

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-172/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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