The vertebral arteries lie within a plane defined by a delta-shaped array of muscles attaching to the vertebral bodies and transverse processes (Fig. 2-2). The longus colli and longus capitis muscles provide anterior support to the cervical vertebrae and bracket the anterior longitudinal ligament of the spine between them. Laterally, the scalene muscles fan out from the cervical transverse processes and insert on the first and second ribs. The lower cervical nerve roots emerge between anterior and middle scalene muscles, while the upper roots appear between the longus capitis and levator scapulae muscles. This muscular delta is covered by prevertebral fascia. The anterior scalene and longus colli muscles converge at the prominent anterior tubercle of the transverse process of C6, sometimes called the carotid tubercle (of Chassaignac). In the inverted “V” formed by the muscles below this landmark, the first portion of the vertebral artery penetrates the prevertebral fascia to ascend through the C6 transverse foramen.

The vertebral arteries originate from the first part of the subclavian arteries close to the origins of the internal thoracic (formerly internal mammary), thyrocervical, and costocervical vessels (Fig. 2-3). These origins are arrayed radially around the subclavian with the vertebral arising superiorly and posteriorly. The first portion of the vertebral arteries passes over the cupola of the lung to reach the scalenovertebral angle.

The venous tributaries that accompany the distal vertebral artery converge to form a single vertebral vein on emerging from the sixth transverse process (Fig. 2-4). The vein enters the proximal subclavian vein just distal to the internal jugular vein. On the left side, the thoracic duct emerges from the posterior thorax, arches over the subclavian artery, and enters the subclavian vein between the internal jugular and vertebral veins.

The cervical sympathetic chain lies on the prevertebral fascia anterior to the longus colli and capitis muscles, which in turn lie anterior to the transverse processes housing the vertebral arteries. The middle cervical sympathetic ganglion lies at about the level of the carotid tubercle, and the inferior ganglion lies posteromedial to the origin of the vertebral artery. The inferior ganglion gives off fibers that wrap around and ascend with the vertebral artery.

The costocervical trunk arises posteriorly from the subclavian. Its cervical division ascends in the deep posterior cervical muscles and communicates with the vertebral along its course and with descending branches of the occipital artery.

Beneath skin and platysma, the sternocleidomastoid muscle and investing fascia constitute the first layer to unroof on the way to the vertebral arteries (Fig. 2-5). The omohyoid muscle runs diagonally between the sternocleidomastoid and the underlying carotid sheath. The carotid sheath lies between the sternocleidomastoid muscle and prevertebral fascia medially, and lateral to the sheath, the scalene fat pad directly overlies the first portion of the vertebral artery.

In and around the fat pad are critical structures that must be respected when approaching the vertebral artery. Medially on the left side is the previously described thoracic duct. Deep to the fat pad laterally, the phrenic nerves descend diagonally across the anterior scalene muscles, pass lateral to the thyrocervical trunks, and dip between subclavian artery and vein to enter the chest. The inferior thyroid artery crosses anterior to the proximal vertebral artery.

Between the transverse processes of the atlas and axis vertebrae, there is more space for access to the vertebral arteries than in other interspaces due to the decreased bulk of the bony arches posteriorly (Fig. 2-6). After emerging through the foramina of the atlas, the arteries take a sharp bend backward and lie in grooves encircling the posterior rims of the bony articular plateaus. They then course anteriorly, medial to the atlantooccipital articulation, and pass through the foramen magnum.

At the level of the posterior groove, the arteries give off branches to the deep muscles of the neck that anastomose with ascending cervical, occipital, and deep cervical arteries. Medial to the articular facets, the arteries give off branches that descend within the vertebral canal, supplying vertebral bodies and meninges. Prior to converging at the level of the pons, small descending branches fuse to form a midline vessel along the ventral surface of the medulla.

The tortuous terminal extracranial vertebral arteries lie deep within the suboccipital muscular triangles and are difficult to expose (Fig. 2-7).

An anterolateral approach to the C1 to C2 segment is possible by detaching the levator scapulae origins from the tips of the transverse processes (Fig. 2-8).

After passing around the posterior part of the articular process, the vertebral artery penetrates first the atlantooccipital ligament and then the dura on its way to the foramen magnum (Fig. 2-9).

There are two main options for exposure of the most proximal portion of the vertebral artery: the transverse supraclavicular approach and the vertical anterior cervical approach. Although the supraclavicular approach affords excellent exposure of the vertebral artery at its origin, the exposure is relatively limited and requires transection of the sternocleidomastoid muscle. The anterior cervical approach does not require muscular transection, and it permits rapid extension of the incision for vascular control of more distal vertebral artery segments. However, exposure of the vertebral artery is more difficult through a cervical incision. In general, the supraclavicular approach is employed for elective operations involving vertebral artery reimplantation into the adjacent common carotid artery, and the anterior cervical approach is favored during emergency explorations for suspected vertebral artery injury.^1,2,3,4