Surgical excision of filum terminale arteriovenous fistulae after lumbar fusion: Value of indocyanine green and theory on origins (a technical note and report of two cases)

BACKGROUND: Intradural filum terminale arteriovenous fistulas (AVFs) are uncommon. We report two cases of this rare entity in which we used indocyanine green (ICG) videoangiography to identify the fistulous connection of each lesion. CASE DESCRIPTION: Two male patients presented with unresolved lower extremity weakness and paresthesias following lumbar fusion surgery. In each case, angiography showed an AVF between the filum terminale artery (FTA), the distal segment of the anterior spinal artery (ASA), and an accompanying vein of the filum terminale. A magnetic resonance image (MRI) obtained before lumbar fusion was available in one of these cases and demonstrated evidence of the preexisting vascular malformation. Surgical obliteration of each fistulous connection was facilitated by the use of ICG videoangiography. This emerging technology was instrumental in pinpointing fistula anatomy and in choosing the exact segment of the filum for disconnection. CONCLUSION: Our findings indicate that intradural filum terminale AVFs may have a congenital origin and that ICG is a useful tool in their successful surgical management. As these cases demonstrate, spine surgeons should remain vigilant in evaluating patients based on their clinical symptomatology, even in the presence of obvious lumbar pathology.