A 60-year-old woman presented with a spinal dural arteriovenous fistula (SDAVF) located in the lower cervical region, which had been asymptomatic for 56 months after the initial detection. She underwent embolization of the SDAVF when she became symptomatic, but her neurological recovery was only partial. Cervical SDAVF is rare but sometimes discovered in an asymptomatic state. The natural history and validity of preventive treatment for asymptomatic SDAVF have not been fully established. Her unfavorable outcome demonstrates the potential advantages of adequate treatment at an early stage even for asymptomatic SDAVF.