Spinal arteriovenous fistula in the lipoma of the filum terminale: A report of two cases and literature review

Abstract

Background: Filum terminale arteriovenous fistulas (FTAVFs) are rare and their pathogenesis remains unknown. The authors report two cases of FTAVF that arose in the lipoma of the filum terminale.

Case description: The two patients were 72 and 76 years of age, and both presented with a progressive paraparesis. The first patient had an arteriovenous fistula (AVF) located at L5 that was supplied by the anterior spinal artery originating from the left T10 intercostal artery. The second patient's AVF at L3-4 was fed by the anterior spinal artery originating from the left T8 intercostal artery. Both patients underwent partial resection of the filum terminale at the location of the shunts. The pathological examinations revealed that both the AVFs were embedded in the adipose tissue of the filum terminale, revealing the fatty fila that were not visible in preoperative magnetic resonance images.

Conclusion: Two cases of FTAVF were successfully treated by obliterating the fistulas through partial resection of the affected fatty filum terminale. The literature review revealed 13 cases of FTAVF concomitant with the lipomas of the filum terminale. Resection and histological evaluation of the filum terminale should be performed to treat and elucidate the pathogenesis of FTAVF.

Keywords: Fatty filum terminale; Filum terminale arteriovenous fistula; Pathology.

Figure 1:

Filum terminale arteriovenous fistula at L5 (Case 1). (a) Sagittal T2-weighted magnetic resonance image (MRI) shows the swollen spinal cord surrounded by flow voids. It also shows redundant cauda equina and spinal canal stenosis from L3 to L5. (b) Sagittal T1-weighted MRI does not show high signal intensity in the filum terminale. (c and d) Axial T1- and T2-weighted MRIs at L5 indicate thickened filum terminale due to edema, although the fatty component is not evident. (e) Selective catheter angiography from left T10 intercostal artery shows an arteriovenous fistula located at L5 that is fed by a caudally running artery in the filum terminale. The drainer is a vein in the filum terminale with an ascending flow.

Figure 2:

Case 1 continued. (a) Intraoperative findings show edematous filum terminale with dilated arteries and veins, (b) Intravenous indocyanine green (ICG) video angiogram shows the artery of the filum terminale (AFT) with a caudal inflow (arrow), connecting directly with the vein in the filum terminale drained rostrally (arrowhead), The transitional point from the artery to the vein was considered as the arteriovenous fistula (AVF) (asterisk), (c) A temporary aneurysm clip is applied on the AFT immediately proximal to the shunting point, (d) intravenous ICG angiogram shows another minor feeding artery (arrow) joining the AVF with a caudal inflow, (e) one more temporary aneurysm clip is applied to the minor feeding artery, (f) the pathological finding of resected filum terminale shows an arterialized vein embedded in the adipose tissue (hematoxylin and eosin stain, ×50).

Figure 3:

Filum terminale arteriovenous fistula at L3-4 (case 2). (a) Sagittal T2-weighted magnetic resonance image (MRI) shows edematous spinal cord and perimedullary flow voids, (b) spinal lipoma is not recognized on sagittal T1-weighted MRI, (c) selective catheter angiography from left T8 intercostal artery shows an arteriovenous fistula located at the L5 level supplied by an artery that originated from the anterior spinal artery.

Figure 4:

Case 2 continued. (a) Intraoperative finding shows edematous filum terminale with dilated arteries and veins. (b) The filum terminale is resected with the arteriovenous fistula (arrow). (c) The histopathological study of the resected filum terminale shows an arterialized vein surrounded by the adipose tissue.