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

Classification

Spinal cord vascular malformations may be divided into intramedullary arteriovenous malformations, perimedullary arteriovenous malformations, spinal-dural arteriovenous fistulas, epidural arteriovenous malformations, paravertebral vascular malformations, vertebral hemangiomas, and complex angiomatosis, including metameric angiomatosis (Cobb's syndrome) and disseminated angiodysplasias (Osler-Weber-Rendu syndrome). Spinal cord cavernomas, telangiectasias, and venous angiomas complete the list, yet are not amenable to endovascular therapy ( Table 1 ).

Intramedullary Arteriovenous Malformations

Intramedullary arteriovenous malformations (AVMs) demonstrate an intervening nidus between an artery and vein, partially or totally, within the spinal cord parenchyma. The anterior spinal and posterolateral spinal arteries supply nearly all intramedullary AVMs, and they drain into engorged medullary spinal veins. Most are found in the cervical or thoracic segments of the spinal cord. If the nidus is compact, the AVM is referred to as a glomus type (or a type II spinal AVM[3]). If the nidus is diffusely infiltrating the spinal cord, it is referred to as a juvenile type (or type III spinal AVM[3,4]).

Spinal artery aneurysms or venous spinal aneurysms occurred in 20% to 40% of patients with intramedullary AVMs, and the presence of a spinal artery aneurysm was associated with a statistically significant increase in the risk of bleeding.[4,5] Metameric angiomatosis was found in 6 of 14 patients (43%) with spinal artery aneurysms.[5,6]

Spinal subarachnoid hemorrhage or acute medullary syndrome is usually the presentation during childhood or adolescence.[4,7,8,9] The clinical course is progressive with deterioration of spinal cord function and recurrent hemorrhage. When the hemorrhage occurs within the spinal parenchyma, it can result in acute-onset neurologic decline or a functionally complete spinal cord transection.

Magnetic resonance imaging (MRI) is the screening modality of choice. Decreased signals on T1- and T2-weighted images, described as "flow voids," delineate the AVM nidus within the spinal cord substance. The myelographic effect of T2-weighted images also demonstrates engorged draining medullary veins and possibly feeding arteries within the cerebrospinal fluid. Intraparenchymal hemorrhage, myelomalacia, and edema are also better delineated by MRI than by any other diagnostic modality. Computed tomography (CT) is clearly inferior.

The complete evaluation of a patient suspected of harboring a spinal AVM then includes selective spinal angiography. Multiple spinal arteries need to be catheterized and studied to evaluate the entire extent of the malformation. Biplane angiography is useful to demonstrate the relationship of the AVM to the spinal cord and canal. Rapid filming (five exposures per second) is imperative to identify feeding artery aneurysms and draining vein aneurysms. Feeding arteries are generally hypertrophied and tortuous. Branches of the vertebral arteries, thyrocervical trunk, costocervical trunk, supreme intercostal, and thoracic intercostal arteries may supply AVMs in the cervical spinal cord.[10] All may need to be catheterized individually. Drainage occurs through dilated medullary veins to radicular veins.

Therapeutic alternatives include endovascular embolization/obliteration, open surgery, or a combination of both. AVMs medially located over the posterior aspect of the spinal cord are more easily accessible following laminotomy than AVMs located lateral and anterior to the spinal cord and supplied by the anterior spinal artery. Surgery may be difficult because of the intramedullary location and the difficulty in distinguishing arteries from arterialized veins. However, over 60% of spinal cord AVMs were removed successfully in one early series with stabilization of the patient's condition or clinical improvement.[11] Intraoperative monitoring with somatosensory evoked potentials may improve clinical outcomes.[12]

Endovascular surgical embolization may be performed in combination with open surgery or as the sole treatment if the feeding arteries are of sufficient caliber.[12,13,14,15] The embolic agent must pass through the anterior and posterior spinal arteries to reach the malformation itself while sparing perforating arteries and draining veins. Embolization can be performed with polyvinyl alcohol (PVA)[13] or biospheres[16,17] if temporary or liquid acrylic agent for permanence. The normal anterior spinal artery diameter is in the range 100 to 340 µm and the diameter of the normal central spinal artery varies between 60 and 72 µm.[18] Therefore, PVA with diameters of 150 to 250 µm should pass through a normal anterior spinal artery without lodging in the central spinal arteries. Often the anterior spinal artery is dilated, allowing the use of larger particles. PVA allows long-term recanalization, however, and necessitates repeated embolization or surgical excision. Embolization with liquid adhesives such as N-butyl cyanoacrylate (NBCA) has the advantage of achieving permanent occlusion with, however, a higher risk of cord infarct. Occasionally, one can reach the nidus itself or feeding artery aneurysm, which can be obliterated with coils.[6] The majority of these procedures are now performed under general anesthesia for clarity of the angiographic images, although evoked potentials can be performed.

Figure 1 demonstrates the MRI and angiographic images of a 28-year-old man presenting with spastic hyperreflexic paraparesis from myelopathy associated with cord edema secondary to a T9 AVM. Figure 1A demonstrates the T1 signal weighted MRI with gadolinium, axial projection. We note high signal within the cord parenchyma representing blood products or edema, or both. Signal voids surrounding the spinal cord represent engorged medullary veins. Figure 1B, the lateral T1-weighted MRI image, better demonstrates the intramedullary serpiginous flow voids highly suspicious for a spinal cord vascular malformation. Spinal angiography (Fig. 1C) demonstrates the main supply derived from a posterolateral spinal artery from the right T10 intercostal artery. This artery was embolized with embospheres, resulting in obliteration of the nidus (Fig. 1D). This was followed by surgical resection. The patient had transient worsening of his preoperative paraparesis and then returned to baseline.

Figure 1.

(A) T1 signal weighted MRI with gadolinium, axial projection, of a 28-year-old man presenting with spastic paraparesis. High signal within the cord parenchyma represents blood products and/or edema. Signal voids surrounding the spinal cord represent engorged medullary veins. (B) Lateral T1-weighted MRI image demonstrating the intramedullary serpiginous flow voids posterior to the T9 vertebral body highly suspicious for a spinal cord vascular malformation. Intramedullary high signal again represents blood products and/or edema. (C) Microcatheter injection of the right T10 radiculomedullary artery, demonstrating a spinal AVM supplied by the posterolateral spinal artery. This artery was embolized with embospheres for occlusion. (D) A right T10 intercostal injection after embolization demonstrating no flow or early shunting within the previously enlarged posterolateral spinal artery (the anterior spinal artery filled by the left T11 intercostal artery).

Figure 1.

(A) T1 signal weighted MRI with gadolinium, axial projection, of a 28-year-old man presenting with spastic paraparesis. High signal within the cord parenchyma represents blood products and/or edema. Signal voids surrounding the spinal cord represent engorged medullary veins. (B) Lateral T1-weighted MRI image demonstrating the intramedullary serpiginous flow voids posterior to the T9 vertebral body highly suspicious for a spinal cord vascular malformation. Intramedullary high signal again represents blood products and/or edema. (C) Microcatheter injection of the right T10 radiculomedullary artery, demonstrating a spinal AVM supplied by the posterolateral spinal artery. This artery was embolized with embospheres for occlusion. (D) A right T10 intercostal injection after embolization demonstrating no flow or early shunting within the previously enlarged posterolateral spinal artery (the anterior spinal artery filled by the left T11 intercostal artery).

Figure 1.

(A) T1 signal weighted MRI with gadolinium, axial projection, of a 28-year-old man presenting with spastic paraparesis. High signal within the cord parenchyma represents blood products and/or edema. Signal voids surrounding the spinal cord represent engorged medullary veins. (B) Lateral T1-weighted MRI image demonstrating the intramedullary serpiginous flow voids posterior to the T9 vertebral body highly suspicious for a spinal cord vascular malformation. Intramedullary high signal again represents blood products and/or edema. (C) Microcatheter injection of the right T10 radiculomedullary artery, demonstrating a spinal AVM supplied by the posterolateral spinal artery. This artery was embolized with embospheres for occlusion. (D) A right T10 intercostal injection after embolization demonstrating no flow or early shunting within the previously enlarged posterolateral spinal artery (the anterior spinal artery filled by the left T11 intercostal artery).

Figure 1.

(A) T1 signal weighted MRI with gadolinium, axial projection, of a 28-year-old man presenting with spastic paraparesis. High signal within the cord parenchyma represents blood products and/or edema. Signal voids surrounding the spinal cord represent engorged medullary veins. (B) Lateral T1-weighted MRI image demonstrating the intramedullary serpiginous flow voids posterior to the T9 vertebral body highly suspicious for a spinal cord vascular malformation. Intramedullary high signal again represents blood products and/or edema. (C) Microcatheter injection of the right T10 radiculomedullary artery, demonstrating a spinal AVM supplied by the posterolateral spinal artery. This artery was embolized with embospheres for occlusion. (D) A right T10 intercostal injection after embolization demonstrating no flow or early shunting within the previously enlarged posterolateral spinal artery (the anterior spinal artery filled by the left T11 intercostal artery).

processing....