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

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.