Complications of Surgery for Spinal Vascular Malformations

Abstract

Spinal vascular malformations (AVMs), particularly intradural intramedullary AVMs (i.e., type II or glomus AVMs), are complex lesions that are often difficult to manage. Their complexity relates to the possibility of injury to the spinal cord and its blood supply, resulting in devastating neurologic injury. A thorough familiarity with normal and pathologic anatomy is important, as is an understanding that leaving residual AVM after embolization and resection is better than causing neurologic injury. For intramedullary AVMs, which are located partially or completely in the spinal cord parenchyma and sometimes bridge the pial surface, we use a pial resection technique that produces excellent results.

Keywords

arteriovenous malformation, intradural intramedullary spinal AVM, pial resection, spinal AVM

Highlights

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Spinal vascular malformations are complex lesions with potentially devastating consequences in the event of spinal cord injury.
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A thorough knowledge of the anatomy and pathophysiology is critical to safely treat patients with these lesions.
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The pial resection technique makes resection of intradural intramedullary spinal arteriovenous malformations safe and effective, with excellent neurologic and angiographic results.

Background

Spinal vascular malformations are complex lesions that represent a clinically significant management challenge. Our understanding of their pathophysiology and our ability to treat these lesions have grown substantially with improvements in microsurgery, endovascular techniques, and neuroimaging. We have developed a modified classification system of these lesions based on their anatomy and pathophysiology. Classification helps organize our understanding and guide the management of spinal vascular malformations, particularly arteriovenous malformations (AVMs). This chapter focuses on the surgical treatment of intradural intramedullary AVMs because dorsal intradural arteriovenous fistulae are less complex and thus less technically challenging, and other spinal vascular malformations are less commonly treated surgically. Intradural intramedullary AVMs, also known as type II or glomus AVMs, are located, at least partially, in the spinal cord parenchyma but frequently bridge the pial surface. We have pioneered the use of the pial resection technique for their removal, which we have applied with excellent results. The pial resection technique is often used in conjunction with preoperative embolization ( Fig. 59.1 ).

Anatomic Insights

Arterial

Longitudinal arteries : The spinal cord vasculature can be conceptualized as a grid with longitudinally oriented vessels fed by transversely oriented vessels. The longitudinal vessels are the single anterior spinal artery and the paired posterior spinal arteries. The anterior spinal artery arises from the bilateral vertebral arteries and runs continuously in the anterior median fissure in the anterior midline. It supplies approximately two-thirds of the spinal cord, including most of the gray matter via both small penetrating and circumferential arteries around the pial surface. The posterior spinal arteries are paired discontinuous arteries that arise from the vertebral arteries and run medial to the dorsal root entry zone. They supply the posterior spinal cord, which comprises approximately one-third of the spinal cord, including the dorsal columns and a small contribution to the central gray matter via small circumferential pial branches.

Segmental arteries : As the longitudinal arteries descend the spinal cord, they are fed by transversally oriented arteries known as segmental arteries. The segmental arteries vary in their origin and their termination. In the cervical spine, they typically arise from the vertebral arteries and the thyrocervical trunk. In the lumbar and thoracic spine, they typically originate from the aorta and iliac arteries. The segmental arteries have numerous and variable transverse and longitudinal anastomoses. Each segmental artery sends a branch to the vertebral bodies before continuing to its final branch point in front of the transverse process. It then divides into an intercostal branch and a dorsal branch. The intercostal branch supplies the ribs and musculature. Along its route, the dorsal branch supplies the posterior elements of the spine and the dural and epidural elements. The continuation of the dorsal branch has one of three possibilities and has been referred to by different nomenclature. The number and location of each branch type are highly variable. At some levels, the artery does not contribute to the spinal cord and supplies only the dura and nerve root; this variation is best termed a radicular artery . Alternatively, the segmental artery may connect with the posterior spinal artery and supply the nerve root and posterior spinal cord, at which point it is best referred to as a posterior radiculopial artery . Finally, it can connect to the anterior spinal artery and supply the nerve root, pia, and intramedullary spinal cord, where it is known as an anterior radiculomedullary artery . The large anterior radiculomedullary artery in the thoracolumbar spine is known by the eponymous term the artery of Adamkiewicz .

Venous

The venous anatomy of the spinal cord is similarly organized and plays a critical role in the pathophysiology of AVM lesions. A network of intramedullary veins drains into the longitudinally oriented intradural extramedullary network, which is connected to the longitudinal epidural plexus through the dura by radicular veins.

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