Spinal dural arteriovenous malformations. Intraoperative evoked potential evidence for pathophysiology. A case report.

Abstract

This case report details intraoperative evoked potential changes during surgical removal of a T8 dural arteriovenous malformation. The pattern of changes in somatosensory-evoked responses during surgical correction of spinal dural at arteriovenous malformation can illuminate the pathophysiologic process behind the clinical symptoms. Arteriovenous malformation of the spinal dura can manifest with multiple symptoms, including progressive myelopathy and pain. The pathophysiologic process behind these symptoms could be either direct compression of the spinal cord by the arteriovenous malformation, ischemia resulting from the cord, or increased venous pressure. To investigate these hypotheses further, the results of posterior tibial evoked potentials obtained during surgical removal of a T8 dural arteriovenous malformation were analyzed. At baseline, the cortical (P40) potential was markedly prolonged bilaterally. During surgery, just after the dura was opened, a marked increase was observed in the latencies of the P40 and P60 components of the evoked response on the right, which began to resolve as soon as the arteriovenous malformation was occluded. Only minimal changes were seen on the left. These results are most consistent with the increased venous pressure hypothesis for the pathogenesis of neurologic symptoms in dural arteriovenous malformations.