Sacral spinal dural arteriovenous (AV) malformation is rare and its clinical features are not specific to differentiate sacral dural AV malformation from the superiorly located ones. A sacral dural AV malformation, therefore, is usually diagnosed after negative thoracic and lumbar arteriograms. In this report, we propose a myelographic or magnetic resonance (MR) sign of engorged and tortuous intradural filum terminale vein as an indication of a sacral dural AV malformation. When this sign is seen, pelvic arteriography should be performed first.