Spontaneous resolution of foramen magnum dural arteriovenous fistula with anticoagulant therapy: A case of antiphospholipid syndrome misdiagnosed as seronegative neuromyelitis optica spectrum disorder

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.

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.

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.