Filum Terminale Arteriovenous Fistula with Additional Arterial Supply by the Lateral Sacral Artery: Neurological Image

Filum terminale arteriovenous fistulas (FTAVFs) are rare lesions, generally characterized by a single direct communication between the artery of filum terminale (AFT) and the vein of filum terminale (VFT). The majority of FTAVFs are fed by AFT. However, FTAVFs may also supply from the lateral sacral artery (LSA) or middle sacral artery. A 66-year-old man presented with a one-year history of progressive weakness and numbness in his lower extremities, along with urinary incontinence. On admission, his neurological examination revealed motor weakness (Grade 2/5) in both legs and decreased sensation below the level of T10. Spinal magnetic resonance imaging (MRI) showed T2-weighted hyperintensity and swelling of the spinal cord. Postcontrast spinal MRI showed prominent enhancement of the perimedullary veins on the surface of the spinal cord, and a dilated and tortuous intradural vein was also noted in the lumbosacral canal [Figure 1]. Spinal angiography revealed a sacral dural AVF (DAVF) at the level of S1 fed by the left LSA. The venous drainage ascended into the perimedullary venous plexus via the dilated VFT. A sacral DAVF with arterial supply from the left LSA was diagnosed. During the operation, a slightly dilated and engorged vessel was found to enter the dura along the left S2 nerve root. The assumed fistula was coagulated and cut [Figure 2]. After surgery, the patient showed mild improvement in his symptoms.Figure 1: Spinal MRI images before the first surgery. Spinal MRI with contrast revealed diffuse T2 hyperintensity (a, thick arrows) and prominent enhancements of the perimedullary veins (b, thin arrows) on the surface of the spinal cord from T4 extending to the lumbosacral canalFigure 2: Preoperative spinal angiography and intraoperative views for the first surgery. (a) Spinal angiography revealed a sacral DAVF (asterisk, fistula) fed by the left lateral sacral artery (LSA), with the dilated and tortuous drainage vein ascending into the filum terminale vein (FTV, white arrows) continuing to the thoracic region. (b, c) Laminectomy of L5-S1 showed a dilated and tortuous draining vein (white arrows) found to enter the dura along the left S2 nerve root. Microsurgical disconnection of the draining vein was performedOne month after the surgery, the patient’s clinical condition deteriorated. MRI showed the persistent edema of the spinal cord, and the dilated and tortuous VFT remained in the lumbar canal [Figure 3]. The second angiography of the left internal iliac artery IIA showed the initial sacral DAVF was completely obliterated. Selective injection of the right T10 intercostal artery showed an FTAVF at the level of L5, which was supplied by the AFT continuing from the artery spinal artery (ASA) with venous drainage via the dilated VFT into the perimedullary venous plexus along the spinal cord [Figure 4]. A rare FTAVF was diagnosed, which was the cause of persistent pathological edema and abnormal vessels of the spinal cord.Figure 3: Preoperative spinal MRI images before the second surgery. Follow-up spinal MRI revealed persistent spinal cord swelling (a, c) and enhancements of the perimedullary veins (b, d, white arrows) around the spinal cordFigure 4: Preoperative spinal angiography before the second surgery. (a) The second spinal angiography of the left LSA revealed that the sacral DAVF was completely obliterated. (b–d) Selective spinal angiography of the right T10 intercostal artery showed an FTAVF (arrowhead, another fistula point) at the level of L4-5, which was supplied by the artery filum terminale artery (FTA) continuing from the artery spinal artery (ASA) with venous drainage via the dilated vein of filum terminale (FTV, white arrows) into the perimedullary venous plexus along the surface of the spinal cordThe long and tortuous ASA made it difficult and unsafe to embolize the fistula. Therefore, a surgical approach was chosen. At surgery, the AFT and dilated VFT along with the filum terminale were identified [Figure 5]. They were coagulated and excised. Spinal MRI after surgery demonstrated a decrease in spinal edema and disappearance of vascular flow voids on the surface of the spinal cord and in the lumbar canal [Figure 6]. The symptoms of the patient gradually improved.Figure 5: Intraoperative views for the second surgery. (a) At surgery, the FTA and dilated FTV along with the whitish filum terminale were identified. (b) They were coagulated and excisedFigure 6: Postoperative MRI images for the second surgery. Spinal MRI after the second surgery demonstrated a decrease of the spinal edema and disappearance of vascular flow voids on the surface of the spinal cord and in the lumbar canalAlthough FTAVF is rare, the possibility of additional blood supply, especially from the LSA, should be considered when diagnosing FTAVF.[1,2] Selective injection of all segmental arteries and both IIAs with a large field of view is required to identify the angioarchitecture of the fistula.[3,4] Both surgical and endovascular approaches are possible options for the treatment of FTAVF and the decision-making should consider the anatomic structure of the fistula. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflict of interest There are no conflicts of interest.