Vascular Myelopathies - Vascular Malformations of the Spinal Cord: Presentation and Endovascular Surgical Management

Louis P. Caragine, Jr., MD, PhD, Van V. Halbach, MD, Perry P. Ng, MD, Christopher F. Dowd, MD

Disclosures

Semin Neurol. 2002;22(2) 

In This Article

Spinal-Dural Arteriovenous Fistulas

Spinal-dural arteriovenous fistulas are the most common variety of spinal cord AVM.[1] Spinal-dural arteriovenous fistulas are thought to be acquired lesions,[4] occur mainly in older adults (mean age of 51 years), and are found more often in men than women. Patients present with slowly progressive myelopathy and radiculopathy,[21,28] which, if left untreated, can progress to paraparesis or quadriparesis.

The arteriovenous fistula is located in the dura itself. The feeding vessels are nonradicular branches of the spinal arteries, small, tortuous arterioles that originate from the dura. The feeding arteries are generally normal in caliber and flow through these lesions is exceptionally slow. A single draining radicular vein is often at the level of the spinal root foramina. The vein is dilated many times the size of the artery and flows retrograde into the anterior and posterior medullary veins and coronal venous plexus surrounding the spinal cord. Chronic venous hypertension and stagnation result in chronic medullary ischemia.[29]

Although phase contrast MRI[24] or dynamic gadolinium-enhanced MRI[25] may increase detection, in our experience these small connections can be easily missed even on excellent quality MRI images. Serpiginous flow voids around the cord may represent flow in dilated medullary veins. The spinal cord may also be enlarged, and intramedullary increased signal on T2-weighted images may represent edema or ischemia secondary to venous hypertension.

Contrast myelography in both the supine position, which can best demonstrate the retromedullary veins, and the prone position reveals dilated and tortuous veins over the dorsum of the cord. If dilated veins are observed, complete spinal angiography is indicated. Image quality must be the best possible to delineate the origin of the shunt. Filming should continue into the late venous phase up to several seconds after the injection.

The majority of patients with the fistula in the thoracic and lumbar region have arterial supply independent of the supply to the spinal cord. Internal iliac artery supply was observed in 12.5% of cases.[30] Endovascular embolization with liquid adhesive can frequently cure these lesions. Initial apparently successful embolization was achieved in 90% of 20 patients in one study; the fistula recurrence rate (failure to occlude the draining vein) for NBCA was 15% (3 patients). All patients who underwent embolization had either improved (55%) or unchanged (45%) gait disability at last follow-up.[31] Not infrequently, complete clinical cure can be achieved in cases presenting with a nonfixed, moderate, neurologic deficit. Recanalization has occurred in cases in which PVA was used as the primary therapy.[32] Open surgery is recommended if embolization fails to occlude the dural arteriovenous fistula.

Figure 3 represents the case of a 58-year-old man with a 4-year history of loss of sensation and proprioception and pain in both feet that progressed to include legs and hip regions as well as bilateral leg weakness. By admission he had developed urinary retention requiring catheterization and bowel retention requiring manual evacuation. On examination he demonstrated 2/5 strength in his lower extremities and 5/5 in the upper extremities. He was wheelchair bound, had a T12 sensory level, and had loss of deep tendon responses in the lower extremities.

Figure 3.

(A) Sagittal first and second echoes of the T2-weighted MRI of the lower thoracic spine demonstrate intramedullary hyperintensity within the conus without cord enlargement and a serpiginous flow voids anterior to the cord (white arrow). (B) Axial T1-weighted MRI of the thoracic spine before (left) and after (right) gadolinium demonstrates cord enhancement. (C) Selective right internal iliac angiogram demonstrates a nidus of AV fistula (between arrows), supplied by the lateral sacral artery and draining by an ascending perimedullary vein (arrowhead). (D) Unsubtracted fluoroscopic image of the pelvis demonstrates the NBCA glue cast at the site of the previous fistula (between arrows).

Figure 3.

(A) Sagittal first and second echoes of the T2-weighted MRI of the lower thoracic spine demonstrate intramedullary hyperintensity within the conus without cord enlargement and a serpiginous flow voids anterior to the cord (white arrow). (B) Axial T1-weighted MRI of the thoracic spine before (left) and after (right) gadolinium demonstrates cord enhancement. (C) Selective right internal iliac angiogram demonstrates a nidus of AV fistula (between arrows), supplied by the lateral sacral artery and draining by an ascending perimedullary vein (arrowhead). (D) Unsubtracted fluoroscopic image of the pelvis demonstrates the NBCA glue cast at the site of the previous fistula (between arrows).

Figure 3.

(A) Sagittal first and second echoes of the T2-weighted MRI of the lower thoracic spine demonstrate intramedullary hyperintensity within the conus without cord enlargement and a serpiginous flow voids anterior to the cord (white arrow). (B) Axial T1-weighted MRI of the thoracic spine before (left) and after (right) gadolinium demonstrates cord enhancement. (C) Selective right internal iliac angiogram demonstrates a nidus of AV fistula (between arrows), supplied by the lateral sacral artery and draining by an ascending perimedullary vein (arrowhead). (D) Unsubtracted fluoroscopic image of the pelvis demonstrates the NBCA glue cast at the site of the previous fistula (between arrows).

Figure 3.

(A) Sagittal first and second echoes of the T2-weighted MRI of the lower thoracic spine demonstrate intramedullary hyperintensity within the conus without cord enlargement and a serpiginous flow voids anterior to the cord (white arrow). (B) Axial T1-weighted MRI of the thoracic spine before (left) and after (right) gadolinium demonstrates cord enhancement. (C) Selective right internal iliac angiogram demonstrates a nidus of AV fistula (between arrows), supplied by the lateral sacral artery and draining by an ascending perimedullary vein (arrowhead). (D) Unsubtracted fluoroscopic image of the pelvis demonstrates the NBCA glue cast at the site of the previous fistula (between arrows).

MRI of the thoracic spine revealed hyperintensity in the spinal cord on T2-weighted images from T11 to the conus without focal cord enlargement and enhancement of the cord on axial T1-weighted MRI (Figs. 3A and 3B). A selective right internal iliac angiogram demonstrates a nidus of AV fistula (Fig. 3C) supplied by the lateral sacral artery and draining by an ascending perimedullary vein. Subselective catheterization using a microcatheter was performed and endovascular surgical obliteration achieved using NBCA (Fig. 3D). Postembolization angiography of both internal iliac arteries and feeding vessels demonstrates no further filling of the fistula.

processing....