Cauda Equina and Filum Terminale Arteriovenous Fistulas: Anatomic and Radiographic Features.

K Namba,N Toma,T Ishiguro,Y Niimi,M Komiyama,A Higaki

doi:10.3174/ajnr.a6813

Abstract

Intradural AVF below the conus medullaris may develop either on the filum terminale or the cauda equina (lumbosacral and coccygeal radicular nerves). Although not a few filum terminale AVFs are found in the literature, only 3 detailed cauda equina AVFs have been reported. Here, we analyze the angiographic and MR imaging findings of our cauda equina and filum terminale AVF cases, supplemented with literature research to characterize the radiologic features of the 2 entities. On angiography, filum terminale AVFs were invariably supplied by the extension of the anterior spinal artery accompanied by a closely paralleling filum terminale vein. Cauda equina AVFs were fed by either a radicular or a spinal artery or both arteries, often with a characteristic wavy radicular-perimedullary draining vein. On thin-section axial MR imaging, the filum terminale AVF draining vein joined the spinal cord at the conus medullaris apex, but that of the cauda equina AVF joined above the conus medullaris apex.

Highlights

We present our cauda equina and filum terminale (FT) AVF cases supplemented by previous reports and discuss the angiographic and MR imaging features of the 2 diseases
Based on the angiographic and MR imaging findings, the diagnosis of cauda equina AVF was made in cases 1 and 2 and FT AVF in case 4
The main findings in the present study were 1) in the FT AVF, the anterior spinal artery (ASA) maintained its course and caliber at the conus medullaris apex, 2) the FT AVF showed a parallel feeder–drainer pattern, 3) the cauda equina AVF had variable feeding arteries, 4) the extension of the ASA involved in the cauda equina AVF changed its course and caliber at the conus medullaris apex, 5) the cauda equina AVF showed a wavy draining vein in 3 of 5 cases, and 6) thin-section axial MR imaging detecting the draining vein may aid in differentiating cauda equina and FT AVFs

Summary

Introduction

In cases 1 and 2, the vein was off the spinal cord at the conus medullaris apex (Figs 4C and 3C, arrowhead) and joined it at the L1 level (Figs 4C and 3C, large horizontal arrow) and was interpreted as radicular. In case 3, surgical findings confirmed the diagnosis of cauda equina AVF.[5]

Results

Conclusion