Management of the Vertebral Artery during Excision of Extradural Tumors of the Cervical Spine

Patient Selection

A variety of extradural tumors can involve the cervical spine. These include chordomas, giant cell tumors, aneurysmal bone cysts, and metastatic tumors. Radical surgical excision and stabilization constitute the primary treatment in the majority of instances. In addition to the bony structures, these tumors often involve the dura, nerve roots, vertebral artery on one or both sides, and soft tissues in the neck. This chapter focuses on the vertebral artery.

The artery is often involved by these tumors in several ways. The vessel may provide blood supply to the tumor, it may be displaced by the tumor or encased by it, or it may impede access to the tumor. Understanding its anatomy and managing it in a planned and methodical manner can significantly aid the surgeon in effectively managing these tumors. The following discussion presumes that the goal of the surgeon is to isolate and preserve the artery.

26.1.1 Anatomical Considerations

The paired vertebral arteries occupy a key position in relation to the cervical spine. Each is in intimate relation to the anterolateral portion of the vertebral bodies, the pedicles, and the transverse processes, as well as the most proximal portion of the cervical spinal nerve roots. They may be of equal size, or there may be a dominant one.

The vertebral artery arises from the subclavian artery. Its course is divided into four segments. The first segment is from its origin to its entry into the transverse foramen of C6 ( ▶ Fig. 26.1). It courses cephalad, medial to the border of the scalenus anterior muscle and lateral to the longus colli, and is accompanied by two vena comitantes. It courses deep to the origins of the scalenus anterior muscle to enter the transverse foramen of C6. The second segment of the vertebral artery begins here and travels through the transverse processes of all the vertebrae. The artery follows a relatively straight course up to the point where it enters the transverse foramen of C2. The third segment of the artery begins here. Within the transverse foramen of C2, it makes a complex course, turning laterally and posteriorly to exit on the superior surface of the C2 transverse foramen. Thus, it exits the upper surface of the transverse foramen of C2 posterior and lateral to its course in the segments below. Between C2 and the C1 transverse foramen, it is somewhat redundant to accommodate for the rotatory movement between the two vertebrae. The artery enters the posteroinferior surface of the C1 transverse process and exits on its anterosuperior surface. After emerging from the transverse foramen of C1, it turns sharply posterior and skirts the joint capsule of the articulation of the occipital condyle and the C1 lateral mass, turning medially and cephalad to enter the dura of the foramen magnum, where the fourth segment of the artery begins. This segment ends where it joins the opposite side vessel to form the basilar artery.

Fig. 26.1 Right-sided neck dissection. The head of the patient is on the reader’s left side. The first segment of the vertebral artery (VA) in the neck. Arrowhead is the right phrenic nerve; *Right scalenus anterior muscle; IJV, right internal jugular vein and carotid sheath.

In its second and third segments, the vertebral artery is surrounded by a venous plexus ( ▶ Fig. 26.2). It is also hidden among short and long muscles that arise and attach at the anterior and posterior tubercles of the transverse processes of the vertebrae. The uncovertebral joints are situated immediately medial to the vertebral artery. The nerve roots travel posterior to the vertebral artery along the superior surface of the transverse processes. Between C2 and C1, the prominent dorsal root ganglion of C2 is situated posterior to the artery ( ▶ Fig. 26.3). The ventral ramus of this root hooks around the posterior and lateral surface of the artery as it travels in an anterior direction.

Fig. 26.2 Right-sided neck dissection. The head of the patient is to the left of the reader. Arrowheads indicate the periosteal sheath and venous plexus that is being progressively opened to expose the vertebral artery (VA). IJV, right internal jugular vein.

Fig. 26.3 Illustration showing the lateral view of the vertebral artery at C2 and C1. The C2 ganglion is just posterior to the artery and the ventral ramus of the root crosses on the lateral aspect of the vessel. CN, cranial nerve.

26.2 Preoperative Preparation

High-resolution magnetic resonance imaging (MRI) is the diagnostic test of choice, as well as that which provides a detailed evaluation of the degree and extent of involvement of the bony structures, the neighboring soft tissues, the thecal sac, the nerve roots, and the vertebral artery ( ▶ Fig. 26.4). This is then supplemented with thin-section computed tomographic (CT) scanning to better evaluate the bony architecture. The vertebral arteries are better visualized using the magnetic resonance (MR) arteriogram that shows the relative size and dominance of the vessels up to their junction with the basilar artery. A balloon test occlusion through a catheter angiogram can be performed when sacrificing the vessel on one side is being considered, although preservation or reconstruction is preferred. Preoperative embolization is of benefit in certain metastatic tumors. Preservation of the artery is planned unless it is markedly narrowed by the tumor, which may indicate invasion of the wall. Because many of these tumors can recur and involve the other vertebral artery, it can be a difficult problem if one artery has already been sacrificed at a prior operation. If tumor involvement is limited to the venous plexus and periosteal sheath, the artery can be preserved. Adventitial involvement requires sacrifice of the artery. This decision is made at the time of surgery while the artery is being isolated.

Fig. 26.4 Axial magnetic resonance imaging of a patient with a chordoma. Arrow indicates the right vertebral artery, which is partially surrounded by the tumor. The relation of the tumor with the longus colli, the thecal sac, and the vertebral body is clearly seen.

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