We present the case of a 57-year-old man with protein S deficiency and left leg deep vein thrombosis (DVT) 5 years earlier, who developed stepwise progressive bilateral lower limb weakness, numbness/paresthesia, gait imbalance, hesitancy of micturition, and constipation in the setting of recurrent left common femoral DVT treated with apixaban. Symptoms amplified with Valsalva, corticosteroids, and postlumbar puncture, with longitudinally extensive midthoracic T2-hyperintense lesion extending to the conus associated with hazy holocord enhancement on magnetic resonance imaging (MRI), raising suspicion for spinal dural arteriovenous fistula (sDAVF). Initial digital subtraction angiography (DSA) was negative for sDAVF. However, cerebral spinal fluid (CSF) was herpes simplex virus (HSV)-2 positive, and he was treated with antiviral therapy. Unfortunately, he continued to worsen despite treatment. Repeat neuroimaging 12 months after initial presentation demonstrated persistent lower thoracic/conus lesion in addition to cauda equina enhancement and subtle dorsal T2-hypointense flow voids. We raised red flags (e.g., lack of clinical prodrome, no herpetic rash, no CSF pleocytosis, and rostral extent of the lesion) that suggested the HSV2 nucleic acid detection was perhaps unrelated to the neurologic syndrome. Given the high index of suspicion for sDAVF, we repeated spinal vascular imaging. Spinal MRA demonstrated dilated right dorsal perimedullary veins from T10 to T11. Repeat DSA revealed a right T10 sDAVF. Microsurgical treatment rather than embolization of the fistula was successful without complication, with significant improvement in motor, sphincter, and to a lesser extent sensory function, with residual gait imbalance after inpatient rehabilitation 3 weeks postoperatively.