Magnetic resonance imaging in cases of spinal dural arteriovenous malformation.

Two patients with spinal dural arteriovenous malformations associated with intramedullary changes confirmed by the T2-weighted magnetic resonance imaging (MRI) scans are reported. The characteristics of the MRI findings for these 2 patients were as follows. 1) In the T2-weighted spin-echo image, intramedullary changes observed by MRI were visualized as a high signal intensity area at the level where delay in venous circulation of the spinal cord was revealed by the angiography of the spinal cord. 2) After the obliteration of the arteriovenous shunt by surgical management, intramedullary changes remarkably decreased and disappeared with the disappearance of swelling of the spinal cord observed preoperatively. After that, the atrophy of the spinal cord was shown. 3) The level, extent, and severity of intramedullary changes were decided by the condition of the level where the radiculospinal vein, as the flowing vein, refluxes into the coronal venous plexus and venous flow occurs through the radiculospinal vein into the epidural veins. We suspect that intramedullary changes shown by the T2-weighted MRI scan chiefly represent edema of the spinal cord, caused by an increase in venous pressure due to venous congestion of the spinal cord. MRI is a very useful diagnostic aid to detect intramedullary changes associated with a spinal dural arteriovenous malformation and to evaluate therapeutic results after surgery.