Spinal dural arteriovenous malformation: report of an unusual case.

We present an unusual case of a spinal dural arteriovenous malformation (AVM) which produced compression radiculopathy of the left S1 nerve root. The nerve root was compressed by epidural vessels, draining vessels, and the nidus, without the characteristic myelographic findings of a dural AVM. No feeding vessels could be identified. It is important to consider the possibility of a spinal dural AVM in middle-aged patients who suffer lumbosacral radiculopathy, even if myelography does not demonstrate the characteristic findings.