58 Spinal Arteriovenous Malformations

10.1055/b-0038-162187

58 Spinal Arteriovenous Malformations

Hubert Lee, Brian Drake, Oliver Holmes, David Houlden, Daniela Iancu, Shawn Malone, and John Sinclair

Abstract

Spinal arteriovenous malformations (AVMs) are rare, complex vascular lesions. Understanding of these lesions has increased thanks to neuroimaging technology. Spinal AVMs are classified into four types: dural or intradural arteriovenous fistula (AVF; type 1) are the most common; intramedullary or glomus AVMs (type 2) can be compact or diffuse; metameric or extradural–intradural AVMs (type 3) involve all tissue types; and perimedullary AVFs (type 4) that also include conus medullaris AVM type. Patients can present with back pain, motor/sensory deficits, myelopathy/radiculopathy, or subarachnoid hemorrhage. Most of the symptoms are related to venous hypertension. Computed tomography (CT), CT angiogram, and magnetic resonance imaging (MRI) of the spinal cord are the initial evaluation imaging. Digital subtraction angiography is the gold standard for spinal AVM visualization and characterization. Both endovascular embolization and microsurgical resection are good options. Microsurgical resection has less incidence of recurrence. The goal for both modalities is to eliminate the fistulous portion of the AVM. Spinal AVMs should be treated on an individual basis in a tertiary center with a group of cerebrovascular and endovascular neurosurgeons. Appropriate clinical and radiological follow-up is mandatory in all spinal AVMs.

Introduction

Spinal arteriovenous malformations (AVMs) were first recognized by Heboldt in 1885 as a cause for subarachnoid hemorrhage. Compared with cerebral AVMs, spinal AVMs are less common with a prevalence of 0.4 in 100,000 people. The management of these lesions can be challenging owing to the complex angioarchitecture, eloquence of involved cord parenchyma, and extent of metameric (type III) lesions.

Major controversies in decision making addressed in this chapter include:

Whether treatment is indicated.
Microsurgery compared to endovascular therapy as the initial treatment for spinal dural arteriovenous fistulas (AVFs) (type I).
Role of radiosurgery in the management of spinal intramedullary AVMs (type II).
Approach to malformations where radiological or anatomical cure without incurring neurological impairment is not possible.

Whether to Treat

Treatment of spinal AVMs is indicated when they are symptomatic or have angiographic warning features ( 1 , 2 in algorithm ). The goal is to improve or stabilize neurological function through the prevention of hemorrhage and reducing venous congestion or vascular steal. The natural history data is limited to small case series suggesting progressive neurological decline and hemorrhage, particularly from type II and III AVMs. Aminoff and Logue reported the outcome of ruptured untreated spinal AVMs; at 6 months, 56% of patients had no motor activity restrictions but most experienced deterioration with only 9% retaining similar status at 3 years, and at this point, over 50% of patients developed paraplegia requiring a wheelchair.

**Algorithm 58.1** Decision-making algorithm for spinal arteriovenous malformations.

A pooled analysis of spinal intramedullary AVMs demonstrated an annual hemorrhage rate of 4%. Previous hemorrhage was a significant risk factor increasing the annual hemorrhage rate to 10%. Immediate treatment following a hemorrhagic event is not mandatory as acute rebleeding is rare.

AVF-type malformations can be successfully managed by microsurgical and endovascular techniques. Perimedullary AVFs (type IV) may prove challenging and associated with neurological morbidity in attempting to catheterize the arterial feeders that are often distal anterior spinal artery branches or surgically approaching anteriorly located lesions. Intramedullary AVMs similarly can be treated with high rates of obliteration by surgical resection or liquid embolic agents; however, the extensive nature of extradural–intradural AVMs rarely permits complete cure. Endovascular embolization is typically the first-line treatment for such lesions with aims to minimize shunting volume and reservation of surgery for decompression of related mass effect.

Anatomical Considerations

The arterial supply of the spinal cord is derived from the anterior spinal artery and paired posterior spinal arteries. Two small branches from the vertebral artery join to form the cranial end of the anterior spinal artery that supplies the ventral two-thirds of the spinal cord. The posterior spinal arteries originate from the vertebral arteries or the posterior inferior cerebellar arteries at the level of the medulla and form a plexus of collaterals that supply the dorsal third of the spinal cord. Both arterial systems receive intermittent input from medullary arteries, the most significant of which is the artery of Adamkiewicz. It typically arises from the left between the T8 and L2 levels and serves as the major blood supply to the lower thoracic and lumbar spine. Valves are absent within intrathecal veins but present in medullary veins as they pierce the dura protecting against intradural, retrograde flow from the Batson (epidural) plexus.

Classification

Development of selective spinal angiography led to their anatomical classification into three categories by Di Chiro et al. Type I lesions are dural or intradural dorsal AVF where a radicular artery dural branch connects directly to the coronal venous plexus at the nerve root sleeve. Dural AVFs are the most common, accounting for 70% of all spinal vascular malformations (▶ Fig. 58.1 ; 5 in algorithm ). Type II lesions include intramedullary or glomus AVMs that can be compact or diffuse and supplied by the anterior or posterior spinal arteries (▶ Fig. 58.2 ; 6 in algorithm ). Type III lesions are metameric or extradural–intradural AVMs that have the potential to involve all tissue types at a given somite level (▶ Fig. 58.3 ; 7 in algorithm ). Djindian et al introduced type IV lesions, ventral perimedullary AVFs, with feeders from the anterior spinal artery. More recently, a new classification system has been proposed by Spetzler et al, recognizing conus medullaris AVMs (▶ Fig. 58.4 ; 8 in algorithm ).

**Fig. 58.1 (a,b)** Artist′s illustration depicting type I intradural dorsal arteriovenous fistula (AVF). Observe the radicular artery dural branch connecting directly to the coronal venous plexus at the nerve root sleeve. This is the most common type of spinal AVF. (Used with permission from Barrow Neurological Institute, Phoenix, AZ.) **(c)** Digital subtraction angiogram with left vertebral artery injection demonstrating a high cervical spinal dural AVF supplied by the vertebral artery at the level of C1. Venous drainage is by a descending tortuous epidural vein.

**Fig. 58.2 (a,b)** Artist′s illustration depicting type II intramedullary or glomus arteriovenous malformations (AVMs). These vascular lesions can be compact or diffuse and supplied by the anterior or posterior spinal arteries. (Used with permission from Barrow Neurological Institute, Phoenix, AZ.) **(c)** Spinal digital subtraction angiogram showing a spinal AVM extending from T12 to L3 with supply mainly from the right T9 level (artery of Adamkeiwicz) and **(d)** the left L2 level with a prominent posterior spinal artery. **(e)** Additional contributions also arise from the right T12, L2, L3, L4, and left L1.

**Fig. 58.3 (a)** Artist′s illustration depicting type III metameric or extradural–intradural arteriovenous malformations (AVMs). This vascular lesions have the potential to involve all tissue types at a given somite level. (Used with permission from Barrow Neurological Institute, Phoenix, AZ.) **(b)** T2 weighted MRI demonstrating spinal cord edema, dilated intramedullary and perimedullary vessels at the conus and dilated vessels within the L3 vertebral body. **(c,d)** Disital subtraction angiogram reveals nidus of AVM at T12 with inferior drainage by perimedullary veins to the vertebral body of L3.

**Fig. 58.4** Artist′s illustration depicting type IV ventral perimedullary arteriovenous fistulas (AVFs), in this illustration a conus medullaris arteriovenous malformation (AVM). (Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

Workup

Clinical Evaluation

Subarachnoid or intramedullary hemorrhage occurs with higher frequency in spinal AVMs. These patients present with acute onset back or suboccipital pain, meningismus, and motor deficits. Described as “le coup de poignard rachidien” by Michon in 1928, it is the spinal equivalent of the “thunderclap” headache experienced with intracranial subarachnoid hemorrhage. Neurological deterioration may also occur gradually presumably due to ischemia from vascular steal. These lesions have relatively equal incidence in males and females with onset typically in the second or third decade.

In contrast, spinal AVFs tend to develop progressive symptoms as a result of venous hypertension within the spinal cord compromising the arteriovenous pressure gradient leading to tissue ischemia and edema. Patients may experience back pain, radiculopathy, paresthesias, spastic paraplegia, urinary incontinence, bowel incontinence, and sexual dysfunction. In a small percentage of patients (15%), acute myelopathy can develop from overwhelming venous congestion referred to as the Foix–Alajouanine syndrome or subacute necrotic myelopathy. There does not seem to be a strict correlation between the spinal level and observed dysfunction. Dural AVFs differ from intradural AVMs as they tend to occur in men in the fifth to sixth decade developing mostly between T6 and L2. They also report exacerbation of symptoms with exertion or changes in posture.

Only gold members can continue reading. Log In or Register to continue