Acute or subacute neurological deterioration without evidence of hemorrhage in a patient with a spinal arteriovenous (AV) malformation has been referred to as "Foix-Alajouanine syndrome." This clinical entity has been considered to be the result of progressive vascular thrombosis resulting in a necrotic myelopathy; it has therefore been thought to be largely irreversible and hence untreatable. The authors report five patients with dural AV fistulas who presented in this manner, and who improved substantially after embolic and surgical therapy. The outcome of these patients indicates that acute and subacute progression of myelopathy in cases of spinal dural AV fistulas may be caused by venous congestion and not necessarily by thrombosis. Therefore, a clinical diagnosis of Foix-Alajouanine syndrome is of little practical use, as spinal cord dysfunction from venous congestion is a potentially reversible process whereas thrombotic infarction is not. This diagnosis may result in suboptimal management. The recognition of nonhemorrhagic acute or subacute myelopathy as a complication of a spinal dural AV fistula is important since what appears to be irreversible cord injury is often treatable by standard surgical techniques.