Case Report: Diagnostic anchoring in spinal dural arteriovenous fistula: a case-based analysis of clinical-radiological mismatch and delayed recognition.

Spinal dural arteriovenous fistula (SDAVF) is an uncommon but treatable cause of progressive myelopathy, and its diagnosis is frequently delayed because early symptoms may be misattributed to lumbar degenerative disease, inflammatory myelopathy, or peripheral neurological disorders. We report a 49-year-old man with progressive bilateral lower-limb weakness and numbness over 1 week, followed by marked deterioration within 2 days. Initial lumbar imaging showed disc bulging and degenerative changes, creating a potential diagnostic anchor; however, the bilateral deficits, rapid progression, gait impairment, and urinary and bowel dysfunction were disproportionate to the lumbar findings. Thoracic magnetic resonance imaging (MRI) demonstrated longitudinal intramedullary T2 hyperintensity extending from T5 to T12 and suspected dorsal serpiginous perimedullary flow voids, suggesting venous congestive myelopathy caused by a spinal vascular lesion. Although inflammatory or demyelinating myelopathy was considered, cerebrospinal fluid examination was deferred at that stage because dorsal perimedullary flow voids and the overall imaging pattern made a vascular etiology more likely and more urgent to confirm. Digital subtraction angiography (DSA) was therefore prioritized and confirmed a right T5 SDAVF. The patient underwent microsurgical disconnection, with postoperative angiography confirming complete obliteration and gradual neurological improvement thereafter. The educational value of this case lies not in a novel imaging feature or treatment strategy, but in illustrating how sequential diagnostic anchoring can delay recognition of SDAVF and how clinical-radiological mismatch should prompt timely angiographic evaluation in patients with rapidly progressive myelopathy.