Cauda equina arteriovenous fistula supplied by proximal radicular artery and concomitant sacral dural arteriovenous fistula: A case report and literature review

Abstract

Background: Cauda equina arteriovenous fistulas (AVFs) fed by the proximal radicular artery are exceedingly rare. Spinal dural arteriovenous fistulas (DAVFs) in the sacral region are rare and usually misdiagnosed. We report a case of a cauda equina AVF with concomitant sacral DAVF. We also review the coexistence of multiple types of spinal vascular malformations in a single patient.

Case description: A 54-year-old man presented with progressive weakness of the lower extremities for 1 month. Magnetic resonance imaging (MRI) of the lumbosacral and thoracic spine showed spinal cord congestion, extending from the conus medullaris to the level of T7, and abnormal tortuous and dilated flow void, running from the level of L5 to T12 along anterior surface of the spinal cord. Spinal angiography demonstrated the fistula at the level of L2 below the conus medullaris. Based on intraoperative findings, the cauda equina AVF supplied by the proximal radicular artery with cranial drainage through the enlarged radicular vein was confirmed and successfully obliterated. Another enlarged arterialized radicular vein running parallel to another cauda equina nerve root is observed with unknown origin. After the operation, the patient showed mild improvement of his symptoms. Follow-up MRI and contrast-enhanced MR angiography revealed an another sacral DAVF vascularized by the lateral sacral artery.

Conclusion: The coexistence of different spinal vascular malformations in a same patient is extremely rare. Most authors of several studies hypothesized that venous hypertension and thrombosis due to the presence or treatment of the first spinal vascular lesion may produce a second DAVF.

Keywords: Cauda equina arteriovenous fistula; Filum terminale arteriovenous fistula; Multiple spinal vascular malformations; Radicular arteriovenous fistula; Sacral dural arteriovenous fistula.

Figure 1:

Sagittal T2-weighted image of the thoracolumbar spine shows abnormal hyperintense T2 signal representing spinal cord congestion extending from the conus medullaris to the level of T7 and intradural flow void from the level of L5 to T12 along anterior surface of the lower spinal cord.

Figure 2:

Anteroposterior views of the left L1 segmental artery angiography in (a) early, (b) middle, and (c) late phases demonstrate filling of the posterior spinal artery supplying the fistula (arrow), located at the level of L2 below the arterial basket of the conus medullaris forming from the bilateral posterior spinal arteries (arrowheads), with cranial drainage into perimedullary veins. (d) Anteroposterior view of flush aortography including lower aorta and bilateral iliac arteries reveals no more supply to the fistula.

Figure 3:

Intraoperative photograph during surgery on prone position after opening the dura. (a) Normal vessels on the filum terminale (black arrows). (b) The fistula is located on the left cauda equina nerve root (asterisk) supplied by the feeding artery (black arrowhead) with cranial drainage through the dilated radicular vein (white arrow) (c) another enlarged arterialized radicular vein (white arrowhead) running parallel to the cauda equina nerve root is observed with unknown origin.

Figure 4:

(a) Sagittal T2-weighted image of the thoracolumbar spine obtained 3 weeks after the operation reveals mild regression of spinal cord congestion and remaining of intradural flow void from L5 to L2. (b) Coronal magnetic resonance myelography of the lumbosacral spine demonstrates abnormal flow void running from the left sacral nerve root to the left-sided conus medullaris, probably representing a dilated radicular vein.

Figure 5:

(a-c) Sequential contrast-enhanced T1-weighted MRI coronal images show early enhanced tortuous and dilated intradural vessel, representing a radicular vein, draining cranially from the left sacral nerve root reaching the conus medullaris.

Figure 6:

Comparing between anteroposterior view of (a) preoperative the left L1 segmental artery angiography in late venous phase and (b) postoperative contrast-enhanced magnetic resonance angiography demonstrates the same venous drainage pattern (arrowheads), representing sharing the common medullary venous channel. The feeder from the left lateral sacral artery (arrows) is noted.