Abstract

Background: Foramen magnum dural arteriovenous fistulas (FMDAVFs) are rare vascular lesions that often present with progressive myelopathy and can mimic inflammatory conditions such as neuromyelitis optica spectrum disorder (NMOSD). While endovascular or surgical treatment is typically required, spontaneous resolution of FMDAVFs is exceptionally rare. This case highlights the importance of considering vascular etiologies in patients with myelopathy and overlapping autoimmune features and explores the potential role of anticoagulant therapy in select cases.

Case Description: A 34-year-old man initially presented with progressive paraparesis, sensory disturbances, and bowel and bladder dysfunction. He was diagnosed with seronegative NMOSD and treated with immunosuppressive therapy without improvement. Upon referral, spinal imaging revealed findings consistent with a dural arteriovenous fistula (DAVF) at the foramen magnum. Before angiography could be performed, the patient developed deep vein thrombosis and pulmonary embolism, prompting a comprehensive hypercoagulability workup that confirmed antiphospholipid syndrome (APS). He was started on long-term anticoagulation. Follow-up imaging demonstrated progressive resolution of spinal cord congestion and eventual complete angiographic obliteration of the FMDAVF. The patient remained asymptomatic at 1-year follow-up.

Conclusion: This case illustrates the potential for spontaneous resolution of FMDAVF in the setting of anticoagulant therapy and underscores the role of thrombosis in the pathogenesis of DAVFs. Careful diagnostic evaluation, including vascular imaging and hypercoagulability testing, is critical in patients with atypical myelopathy. In selected patients with underlying thrombotic conditions such as APS, conservative management with anticoagulation may offer a noninvasive therapeutic alternative.

Keywords: Antiphospholipid syndrome, Foramen magnum dural arteriovenous fistula, Seronegative neuromyelitis optica spectrum disorder, Spontaneous resolution, Venous thrombosis

INTRODUCTION

Foramen magnum dural arteriovenous fistulas (FMDAVFs) are exceptionally rare vascular lesions that present unique diagnostic and therapeutic challenges due to their location near critical neurovascular structures. While these fistulas are typically managed with endovascular or surgical intervention to prevent progressive myelopathy, spontaneous occlusion of FMDAVFs is exceedingly uncommon. Nevertheless, a few reports have documented complete clinical and angiographic resolution without invasive treatment.[ 4 , 11 ]

Antiphospholipid syndrome (APS), an autoimmune disorder characterized by a hypercoagulable state, is a known risk factor for venous and arterial thrombosis.[ 2 ] The pathophysiological overlap between APS and dural arteriovenous fistulas (DAVFs) suggests that thrombotic processes may play a pivotal role in the formation and progression of DAVFs. Misdiagnosis is common, as the clinical manifestations of DAVFs can mimic other conditions, such as neuromyelitis optica spectrum disorder (NMOSD), especially in cases presenting with myelopathy and seronegative antibody profiles.[ 13 ]

This report describes the unique case of a young male with APS who was initially misdiagnosed as seronegative NMOSD. The patient developed progressive neurological symptoms, deep vein thrombosis (DVT), and a foramen magnum DAVF, which resolved spontaneously following anticoagulant therapy. This case underscores the importance of comprehensive diagnostic evaluation, including vascular imaging and hypercoagulability testing, to identify structural abnormalities and guide appropriate management. It further highlights the potential for anticoagulation as a noninvasive treatment option in select cases of DAVFs associated with thrombotic disorders.

CASE REPORT

A 34-year-old man presented to another hospital with progressive paraparesis and numbness persisting for 2 months, followed by the development of bowel and bladder dysfunction 1 month later. Magnetic resonance imaging (MRI) of the lumbosacral spine revealed two small, well-defined enhancing lesions at the cauda equina roots, suggestive of nerve sheath tumors. Brain MRI demonstrated patchy hyperintense lesions in the periventricular white matter of the parieto-occipital lobes and an abnormal hyperintense lesion at the craniocervical junction [ Figures 1a and b ].

Figure 1:

(a) Axial T2-weighted image of the skull base shows abnormal hypersignal intensity (black arrowhead) at the posterior part of the cervicomedullary junction with subtle flow voids. (b) Axial fluid-attenuated inversion recovery image of the brain reveals patchy hyperintense signals in the periventricular area. (c) Sagittal T2-weighted and (d) contrast-enhanced T1-weighted images obtained 8 months after the initial symptoms demonstrate swelling and congestion of the cervical cord from C3 to C5 with enhancing perimedullary anterior and posterior cord veins. (e) Sagittal T2-weighted and (f) contrast-enhanced T1-weighted images obtained 18 months after initial symptoms show marked reduction in cord swelling and congestion, with decreased enhancement of posterior perimedullary veins. (g) Anteroposterior and (h) lateral views of a right occipital artery (OA) injection illustrate a dural arteriovenous fistula at the right side of the foramen magnum (FM) with drainage into the anterior spinal vein (arrows). (i) Sagittal maximum intensity projection image from angiographic CT demonstrates the fistulous point at the right side of the foramen magnum, indicated by a white arrowhead. (j) Coronal maximum intensity projection image highlights the venous drainage pathway from the fistula, with the star symbol marking the bridging vein connecting to the spinal venous system and (k) coronal maximum intensity projection reformatted images from angiographic computed tomography of the right OA, along with (l) a 3D reconstruction image, clearly demonstrate the fistulous point (white arrowheads) at the right side of the FM.

The patient reported undergoing a lumbar puncture, although the results were unavailable. Serum testing for anti-aquaporin-4 immunoglobulin G (AQP4-IgG) antibodies was negative. Based on these findings, he was diagnosed with seronegative NMOSD by a neurologist. He was treated with intravenous methylprednisolone pulse therapy for 5 days. However, his lower limb weakness progressively worsened. Subsequent plasma exchange therapy was initiated, and he was maintained on oral prednisolone and azathioprine for several months. During this time, his weight increased significantly from 64 kg to 100 kg. Due to persistent symptoms, rituximab therapy was planned but could not be initiated due to financial constraints. Six months later, the patient was referred to our institution for further evaluation and management.

On neurological examination, the patient exhibited spastic paraparesis (grade 3–4/5). After reviewing the MRI from the prior hospital, abnormal flow voids at the cervicomedullary junction were suspected. Subsequently, cervical MRI was performed, revealing abnormal T2 hyperintense signals consistent with spinal cord congestion from C3 to C5, accompanied by subtle intradural flow voids. Contrast-enhanced imaging revealed perimedullary vessel enhancement along the anterior and posterior surfaces of the spinal cord, highly suggestive of a cervical DAVF [ Figures 1c and d ]. Angiography was scheduled for a definitive diagnosis within 1 week.

Before angiography could be performed, the patient developed bilateral leg swelling, and elevated D-dimer levels (584 ng/mL) indicated DVT, which was confirmed by venous Doppler ultrasonography. Shortly thereafter, he developed chest pain and was diagnosed with a pulmonary embolism. Due to the absence of a chest physician or cardiovascular thoracic specialist at our institute, the patient was transferred to another hospital, where he received anticoagulant therapy. During this period, he also developed colitis and a right scrotal abscess, necessitating an orchidectomy.

Ten months later, the patient returned to our institute. His neurological symptoms had significantly improved. MRI demonstrated significant resolution of spinal cord congestion and perimedullary vein enhancement [ Figures 1e and f ]. Cerebral angiography revealed a FMDAVF, supplied by a branch of the right occipital artery. The fistula drained into the anterior and posterior spinal veins through a bridging vein and was classified as Cognard type V [ Figures 1g - l ]. The patient declined surgery due to symptomatic improvement.

Comprehensive hypercoagulability testing confirmed a diagnosis of APS with positive lupus anticoagulant. The patient was subsequently initiated on long-term anticoagulant therapy. Follow-up MRI at 3 and 6 months showed progressive resolution of enhancing perimedullary veins [ Figures 2a - d ]. Angiography confirmed the complete obliteration of the DAVF [ Figures 2e - h ]. At the 1-year follow-up, the patient remained asymptomatic.

Figure 2:

(a and b) Sagittal T2-weighted and contrast-enhanced T1-weighted images obtained 3 months after the initial angiography demonstrate significant reduction of enhancing perimedullary veins along both anterior and posterior spinal surfaces. (c and d) Corresponding images at 6 months show the disappearance of enhancing perimedullary veins. (e and f) Anteroposterior views during the arterial and late venous phases, and (g and h) lateral views during the arterial and late venous phases of the right occipital artery injection confirm complete obliteration of the foramen magnum dural arteriovenous fistula.

DISCUSSION

FMDAVFs are rare intracranial vascular malformations, accounting for approximately 1.5–2.3% of all intracranial DAVFs. These lesions are located near the craniocervical junction and involve complex angioarchitecture with various feeding arteries, such as the neuromeningeal trunk of the ascending pharyngeal artery, vertebral artery branches, and occipital artery. FMDAVFs typically drain into medullary bridging veins and may present with either congestive myelopathy or subarachnoid hemorrhage depending on the direction of venous drainage. Due to their rarity and overlapping clinical features with other neurological disorders, including NMOSD, FMDAVFs are often misdiagnosed. While most FMDAVFs are treated successfully with endovascular embolization or microsurgery, spontaneous occlusion is extremely rare. Proper diagnosis requires high-resolution vascular imaging, and treatment strategy must be tailored to the fistula’s specific anatomy, venous drainage pattern, and arterial supply. Understanding these features is essential for preventing complications and optimizing clinical outcomes.[ 4 , 7 , 11 , 12 ]

NMOSD is autoimmune inflammatory conditions of the central nervous system characterized by episodes of optic neuritis, transverse myelitis, and other neurological manifestations, primarily linked to AQP4-IgG antibodies. In seronegative NMOSD, diagnosis relies on clinical criteria, imaging findings, and, in some cases, alternative biomarkers like MOG antibodies. Structural abnormalities, such as DAVFs, which can mimic NMOSD symptoms, must be excluded through vascular imaging to avoid misdiagnosis and inappropriate treatments. This underscores the importance of a comprehensive diagnostic evaluation, particularly in seronegative cases, to differentiate NMOSD from structural vascular abnormalities effectively.[ 5 , 13 ]

APS is a systemic autoimmune disorder characterized by the presence of persistent antiphospholipid antibodies, which include lupus anticoagulant, anticardiolipin antibodies, and anti-β2 glycoprotein I antibodies. These antibodies promote a hypercoagulable state that can lead to arterial, venous, or microvascular thrombosis, as well as obstetric complications such as recurrent miscarriages and preeclampsia. APS can be primary or secondary to other autoimmune conditions, notably systemic lupus erythematosus. Its pathogenesis involves both thrombotic and inflammatory mechanisms, including complement activation and endothelial dysfunction. Diagnosis is based on clinical criteria and laboratory confirmation of antiphospholipid antibodies on two occasions at least 12 weeks apart. Treatment typically focuses on long-term anticoagulation to prevent thrombotic events, although emerging research is investigating targeted therapies to address the inflammatory aspects of the disease.[ 2 , 3 ]

The identification of DVT in this patient was a key indicator leading to the diagnosis of APS. This aligns with studies linking APS to an increased risk of venous thromboembolism (VTE). In Thai patients, VTE is less frequently associated with genetic mutations like factor V Leiden or the prothrombin gene mutation, which are common in Caucasians. Instead, acquired factors such as malignancy and autoimmune conditions like APS are more prominent contributors. The detection of DVT prompted a comprehensive hypercoagulability workup, which confirmed APS through the presence of lupus anticoagulant, consistent with findings in Thai studies that highlight APS and elevated clotting factors, such as Factor VIII, as significant thrombosis risk factors.[ 1 ]

The patient’s colitis and scrotal abscess may have been secondary to microvascular thrombosis associated with APS, which can impair local immunity, promote inflammation, and increase susceptibility to infection. Thrombosis of scrotal veins, though rare, has been reported in the literature and can mimic conditions such as epididymitis or testicular torsion, sometimes leading to unnecessary surgery. In this case, the need for orchidectomy may have resulted from ischemic damage triggered by APS-related thrombosis. These findings highlight the importance of considering thrombotic etiologies in APS patients presenting with unusual inflammatory or infectious symptoms, as early anticoagulation may help prevent irreversible complications.[ 8 - 10 ]

The current case of FMDAVF that resolved spontaneously following anticoagulant therapy demonstrates a potential link between thrombosis and DAVF pathogenesis. This finding aligns with a reported case of a patient with protein C deficiency who developed de novo DAVF after thrombosis, which also resolved spontaneously with anticoagulation. These cases underscore the role of venous thrombosis in the formation and progression of DAVFs.[ 6 ]

Thrombosis can induce venous hypertension, leading to compensatory vascular changes such as neovascularization and the development of arteriovenous shunting. In the setting of thrombophilic conditions, the risk of thrombosis and subsequent vascular remodeling is further heightened. The patient in this study was diagnosed with APS, which likely contributed to the thrombotic environment conducive to DAVF formation.

The resolution of the DAVF with anticoagulant therapy suggests that treating the underlying thrombotic process may reverse the vascular changes associated with DAVFs in certain cases. This observation supports the hypothesis that DAVFs, particularly those associated with thrombosis, may not always require invasive treatment and could potentially be managed conservatively with anticoagulation in select patients.

This case also reflects the emerging concept of “disease self-healing,” as described by Yang,[ 14 ] in which spontaneous remission is not merely a rare coincidence but a biological process that can be better understood and potentially applied in clinical practice. The spontaneous resolution of the foramen magnum DAVF in our patient following anticoagulant therapy supports this idea. Instead of relying entirely on invasive interventions, natural physiological processes such as clot resolution, restoration of venous drainage, and vascular remodeling may contribute to fistula regression when appropriately supported by medical treatment. This observation aligns with the concept that future therapies could be developed to enhance or replicate these self-healing mechanisms, offering more personalized and less invasive treatment options for vascular conditions like DAVFs.

CONCLUSION

This case highlights the importance of thorough diagnostic evaluation in patients presenting with myelopathy, particularly when clinical features overlap with autoimmune conditions such as NMOSD. The spontaneous resolution of a FMDAVF following anticoagulant therapy underscores the potential role of thrombosis in DAVF pathogenesis and supports the feasibility of noninvasive management in select cases. Comprehensive vascular imaging and hypercoagulability testing are essential for accurate diagnosis and appropriate treatment planning.

Our report further emphasizes the pathophysiological link between hypercoagulable states and DAVF formation and presents anticoagulation as a potential therapeutic strategy when thrombosis is identified as a contributing factor. The case is notable for its initial misdiagnosis as seronegative NMOSD, the subsequent identification of APS as the underlying etiology, and the complete angiographic resolution of the DAVF with conservative management. These findings contribute to the evolving understanding of vascular anomalies associated with thrombophilia and may inform future diagnostic and therapeutic approaches.

Ethical approval:

Institutional review board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

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