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

Perimedullary Arteriovenous Malformations

Perimedullary AVMs are direct fistulas between a spinal artery and a medullary vein. Most are located on the surface of the spinal cord, are fed by the anterior or posterolateral spinal arteries, and occur near the conus medullaris. These are thought to be congenital lesions. Patients present with progressive paraparesis secondary to venous hypertension or acute deterioration due to rupture of a feeding artery aneurysm.[10] Although most perimedullary AVMs occur in adults, they must be considered as a cause of slow progressive paraparesis in children.[19]

Three types of perimedullary AVMs can be defined on the basis of angiographic findings. In type I the fistula is small and barely detectable. The fistula itself is at the point where there is a change in the vascular caliber; venous drainage frequently ascends over the dorsal cervical cord and is minimally dilated. In type II there is dilatation of the feeding artery, the shunt site, and the draining vein. In type III we see a giant fistula with multiple feeding arteries and a giant feeding vein.[4,20,21,22] Perimedullary AVMs are also known as type IV spinal cord arteriovenous malformations in the literature.[23]

Type I perimedullary AVMs may be difficult to see with MRI because of their small size. Phase contrast MRI[24] or dynamic gadolinium-enhanced MRI[25] may increase detection. An intramedullary increased signal on T2-weighted images is nonspecific and due to venous hypertension. Selective spinal angiography is mandatory to confirm the diagnosis and demonstrate the feeding arteries and veins.

Surgical clipping of the fistula site is the best therapy for type I lesions if the feeding vessel is too small for selective catheterization. Type II fistulas can be approached by endovascular means and cured with NBCA injection into the fistula site. If a complete cure with a glue injection is not possible, particulate embolization can be followed by surgical excision of a more manageable lesion. Type III lesions can be attacked with a combination of detachable or pushable coils and balloons or NBCA injection with adjunctive surgery if necessary. Endovascular intra-arterial injection of indigo carmine dye has also been described as an adjunct to aid with orientation of the vascular anatomy during surgery.[26] Neurologic morbidity remains higher with these lesions.

Ten patients with giant intradural spinal arteriovenous fistulas (perimedullary types II and III) have been described.[27] Three patients were treated with embolization alone or in combination with surgery (seven patients). Eight patients were classified with perimedullary type III and two with perimedullary type II. Seven patients had their fistula cured (as demonstrated by angiography); two patients had 5% residual filling and were scheduled for future therapy. One complication was related to embolization-rupture of the anterior spinal artery by a detachable balloon, resulting in transient worsening of paraplegia with recovery to baseline. Transient worsening of symptoms after endovascular surgery was common, but all patients returned to baseline or better. Dramatic improvement was observed in four patients.

Figure 2 demonstrates the case of a 31-year-old physician with bladder dysfunction, progressive left leg weakness, and difficulty walking occurring over 5 years. MRI reveals a large signal void adjacent to the conus producing bony erosion of the vertebral body (Fig. 2A). Spinal angiography of a left L2 lumbar artery reveals multiple tortuous spinal arteries entering a varix (arrow) with washout of contrast at this point from other feeding vessels entering separately (Fig. 2B). The multiplicity and tortuosity of the feeding arteries suggested the option of a transvenous approach. A microcatheter was navigated from the femoral vein through the lumbar epidural plexus and into draining medullary veins and finally into the giant varix (Fig. 2C). Multiple platinum coils were deposited into the varix for a significant reduction in shunting. The patient developed back pain without neurologic deficit and was given heparin for 48 hours with resolution of pain. Two months later, a second transvenous procedure with the addition of coils and silk suture was accomplished. Again the procedure was followed by back pain, this time treated with glucocorticoids and morphine. Ten days later the patient developed decreased sensory and left leg motor function. An angiogram showed complete thrombosis of the fistula (Fig. 2D). His motor and sensory function improved over the next several weeks to better than baseline. He was able to walk several miles and climb stairs without difficulty. His bladder function remained unchanged. Four years later, he developed a slight increase in leg weakness and reexamination disclosed a small fistula fed now by internal iliac collaterals too small to permit endovascular therapy. Laminectomy and excision of the small fistula and thrombosed varix were accomplished without further neurologic morbidity.

Figure 2.

(A) Sagittal T1-weighted MRI demonstrates a large signal void adjacent to the conus producing bony erosion of the vertebral body. (B) Left L2 lumbar arterial injection, anteroposterior projection, reveals multiple tortuous spinal arteries entering a varix (arrow) with washout of contrast at this point from other feeding vessels entering separately. (C) A microcatheter was navigated from the femoral vein through the lumbar epidural plexus and draining medullary veins into the giant varix, and contrast material was injected in the anteroposterior projection. (D) Left L2 lumbar arterial injection, anteroposterior projection, status after stage 2 transvenous embolization with multiple platinum coils and silk suture deposited into the varix. Complete thrombosis of the fistula was achieved.

Figure 2.

(A) Sagittal T1-weighted MRI demonstrates a large signal void adjacent to the conus producing bony erosion of the vertebral body. (B) Left L2 lumbar arterial injection, anteroposterior projection, reveals multiple tortuous spinal arteries entering a varix (arrow) with washout of contrast at this point from other feeding vessels entering separately. (C) A microcatheter was navigated from the femoral vein through the lumbar epidural plexus and draining medullary veins into the giant varix, and contrast material was injected in the anteroposterior projection. (D) Left L2 lumbar arterial injection, anteroposterior projection, status after stage 2 transvenous embolization with multiple platinum coils and silk suture deposited into the varix. Complete thrombosis of the fistula was achieved.

Figure 2.

(A) Sagittal T1-weighted MRI demonstrates a large signal void adjacent to the conus producing bony erosion of the vertebral body. (B) Left L2 lumbar arterial injection, anteroposterior projection, reveals multiple tortuous spinal arteries entering a varix (arrow) with washout of contrast at this point from other feeding vessels entering separately. (C) A microcatheter was navigated from the femoral vein through the lumbar epidural plexus and draining medullary veins into the giant varix, and contrast material was injected in the anteroposterior projection. (D) Left L2 lumbar arterial injection, anteroposterior projection, status after stage 2 transvenous embolization with multiple platinum coils and silk suture deposited into the varix. Complete thrombosis of the fistula was achieved.

Figure 2.

(A) Sagittal T1-weighted MRI demonstrates a large signal void adjacent to the conus producing bony erosion of the vertebral body. (B) Left L2 lumbar arterial injection, anteroposterior projection, reveals multiple tortuous spinal arteries entering a varix (arrow) with washout of contrast at this point from other feeding vessels entering separately. (C) A microcatheter was navigated from the femoral vein through the lumbar epidural plexus and draining medullary veins into the giant varix, and contrast material was injected in the anteroposterior projection. (D) Left L2 lumbar arterial injection, anteroposterior projection, status after stage 2 transvenous embolization with multiple platinum coils and silk suture deposited into the varix. Complete thrombosis of the fistula was achieved.

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