[Spinal dural arteriovenous fistulae: exacerbation after myelography with metrizamide]

Metrizamide dorsal myelography was performed in two patients with minor to moderate sensorimotor paraparesis. Direct and indirect myelographic signs of spinal arteriovenous aneurysm were seen and spinal cord angiography showed thoracic dural arteriovenous fistulae (AVF) in both cases. Within 24 hours following myelography, clear neurological worsening occurred, associated with cephalalgia, nausea and transient diplopia in one case, leading to paraplegia in a few days. Paraplegia was complete six months after surgery in one case, and had resolved after embolization of fistula in the other patient. The mechanism of neurological worsening may include: substraction of cerebrospinal fluid, sitting position during and after myelography and local increase of metrizamide concentration secondary to impaired resorption caused by the fistula. Water-soluble myelography is of invaluable aid in the diagnosis of dural AVF and must be followed by early angiography, thus allowing prompt therapeutic embolization.