Spontaneous resolution of low-flow spinal arteriovenous fistulas.

Abstract

Spinal vascular anomalies with arteriovenous blood shunting include spinal arteriovenous malformations (SAVMs) and spinal arteriovenous fistulas (SAVFs), which are distinguished by the presence or absence of an interposed nidus. SAVFs can be further characterized based on their location (perimedullary, dural, or extradural) and flow pattern (high-flow versus low-flow shunts). The spontaneous resolution of a spinal vascular malformation, i.e., the complete disappearance-in the absence of therapeutic measures-of a lesion previously identified by angiography, seems to represent an exceptional phenomenon. This study retrospectively analyzed seven patients with spontaneously resolving spinal vascular malformations observed by the senior author between January 2008 and April 2017. A total of 143 spinal vascular malformations were angiographically evaluated during the considered time period, including nine spontaneously resolving SAVFs in six patients, seven spinal epidural fistulas, and two spinal dural arteriovenous fistula. The "spontaneous" resolution of spinal vascular malformations appears to selectively involve SAVFs. While vessel wall alterations previously documented on the venous side of SAVFs may play an important role in the regression of these lesions, angiography seems to represent a significant contributing factor, probably through the prothrombotic properties of nonionic contrast agents.