Veins of the Spine

There are internal and external vertebral plexuses from skull base to sacrum. These veins are essentially without valves, allowing bidirectional flow. As discussed in the prior section, these plexuses contribute to one of the two main drain age routes of the head (the other being the jugular veins). In fact, these may provide the dominant drainage from the head in the upright position or when an IJV is obstructed. These may also provide a dominant drainage route when the ICV is obstructed or in with pregnancy (especially when supine). Overall, there are widespread communication with the systemic venous system including veins of the thoracic cavity (including intercostal and azygous veins), abdominal cavity (including the left renal vein, ascending lumbar veins, and IVC) and pelvic veins (accounting for spread of pelvic malignancies to the internal vertebral (Batson's) plexus).

The internal vertebral plexus is located within the epidural space from the foramen magnum to the sacral hiatus. This internal plexus drains venous blood from both the vertebral column (via the basivertebral vein) and blood from the spinal cord. Typically, and anterior internal vertebral plexus (usually dominant) with paired longitudinal veins and a posterior internal vertebral plexus with two paired longitudinal veins are described. The posterior internal venous plexus may be diminutive or absent in the cervical region.

The external vertebral plexus has anterior and posterior portions, associated with the surface of the vertebral bodies (anterior) and posterior elements communicating with veins of the adjacent musculature (posterior). The intervertebral veins course along with the nerves within the neural foramen, connecting the internal and external venous plexuses. Additionally, a venous plexus is located along the surface of the spinal cord consisting largely of three anterior and there posterior longitudinal veins.

Intra-osseous veins are present within the vertebral bodies. These principally drain to the basivertebral vein, which are readily recognized on imaging examinations, which in-turn drain to the internal vertebral plexus.

In the cervical spine, venous plexus or vertebral veins course along with the vertebral arteries. From C2-C6, the 'vertebral vein' is essentially a plexus that surrounds the vertebral arteries. Below the level of C6, the vertebral vein can be identified as a discrete tubular vascular structure. In reality, on CTV the vertebral vein below C6 may appear to be more a continuation of a posterior muscular vein than the plexus around the vertebral arteries.

In the lumbar spine, lumbar veins encircle the vertebral bodies alongside the lumbar arteries. These drain the internal vertebral and posterior external vertebral plexuses generally into the IVC. Ascending lumbar drains extend from the common iliac veins to the azygous system, coursing anterior to the transverse processes.

References

Carpenter K et al. Revisiting the vertebral venous plexus-a comprehensive review of the literature. World Neurosurg 2021;145:381-395

Borg N et al. Anatomy of spinal venous drainage for the neurointerventionalist: from puncture to neural foramen. AJNR 2022;

The venous drainage of the cervical spine is largely mediated by the vertebral veins. The vertebral veins start as a plexus surrounding the vertebral artery at the skull base and continues to accompany or even surround the vertebral vein inferiorly to the C6 level. Inferior to C6, the vertebral vein becomes a vein proper anterior to the vertebral artery. The vertebral veins communicate with the internal vertebral venous plexus and branches of the paraspinal musculature.

Coronal CT Neck shows the right vertebral vein (blue arrows). In the neck, the vertebral vein follows the vertebral artery. This 'vein' appears like a plexus around the vertebral artery throughout the cervical spine as the artery ascends through the foramen transversarium (typically C1-C6). Caudal to this, the vein becomes better defined as a circumscribed vessel within the soft tissues of the neck. Superiorly, this plexus communicates with the marginal sinus at the foramen magnum.

The venous drainage of the thoracic spine to the central circulation is largely mediated by the azygos system, ultimately draining to the SVC.

The venous drainage of the lumbar spine includes the ascending lumbar veins which drain to the azygos system, direct drainage to the IVC, and drainage to the IVC via the left renal vein. Like elsewhere in the spine, there is an anterior and a posterior internal vertebral venous plexus with 2 anterior and 2 posterior longitudinal veins respectively.