Anatomy of Spinal Venous Drainage for the Neurointerventionalist: From Puncture Site to Intervertebral Foramen

The venous drainage of the spine can be separated into 3 compartments, from medial to lateral. The intradural compartment is further subdivided into intrinsic and extrinsic components. The extradural compartment refers to the epidural venous plexus, also referred to as the internal vertebral plexus. The paraspinal compartment is also called the external vertebral plexus. Efferent pathways are arranged in a segmental fashion, carrying venous blood toward the great veins and on to the right atrium.

A–C, The epidural plexus is richest in 2 anterolateral and 2 posterolateral columns. The 4 columns are joined by circumferential rings surrounding the thecal sac at the midlevel of each vertebral body. When viewed from anterior to posterior, the 4 columns, rings, and foraminal veins form a characteristic hexagonal shape. D, The composite view of the anterior and posterior columns on a frontal view is referred to as the lateral epidural plexus.

A, Coronal view in the cervical region showing that the rich plexus adjacent to the vertebral bodies is anatomically continuous and functionally analogous to the epidural plexus. Inferiorly, the paravertebral plexus condenses into the vertebral veins. B and C, Vertebral venograms rapidly opacify the paravertebral plexus, foraminal veins, and epidural plexus. Filling defects just adjacent to the vertebral bodies represent the pedicles. The more lateral filling defects represent the vertebral artery running through transverse foramina. Between adjacent pedicles is the foraminal vein. Lateral to the pedicle is the paravertebral plexus; medial to it is the epidural plexus, with its characteristic hexagonal shape. v indicates vein; vv, veins.

Examples of the appearance of the lateral epidural space at different levels. Subtracted (A) and unsubtracted (B) microcatheter venography performed at the left T2 lateral epidural plexus fills the foraminal veins. In this case, the guide catheter is in the left brachiocephalic vein. The microcatheter enters the left C6 foramen via the vertebral vein, before forming a hairpin turn and traveling caudally across 3 levels through the lateral epidural plexus. C, Postembolization conebeam CT in a different patient shows the embolic agent within the right T8 and T9 foraminal veins and the adjacent lateral epidural plexus.

Overview of the azygos system and its main tributaries. The right mainstem bronchus is included as a landmark for the arch of the azygos vein. R indicates right; L, left; v, vein.

Subtracted (A) and unsubtracted (B) views of azygos venography. To the right of the vertebral bodies, the guide catheter is seen to ascend from the IVC to the SVC, before coursing backward into the azygos vein. The trachea and carina are seen in relation to the arch of the azygos vein. Numerous venous stumps (black arrows) along the azygos vein represent reflux into paraspinal veins at each level. In this image, an embolic agent cast is seen filling the right superior intercostal vein (white arrow), which drains into the superior aspect of the arch of the azygos. There is also some opacification of 2 bronchial veins (asterisks).

Subtracted (A) and unsubtracted (B) images showing a 6F guide catheter crossing the midline from the azygos to the hemiazygos vein at the level of T9. Also apparent is the hexagonal shape of the epidural plexus, with a central filling defect at the level of the intervertebral disc. The subtracted image below shows the corresponding bony landmarks.

Venography performed with a catheter in the superior aspect of the left internal jugular vein (larger and more lateral, black arrow) shows contrast draining via the condylar vein (asterisk) into the vertebral vein (medial and smaller, white arrow), which inferiorly drains into the junction of the internal jugular vein with the left brachiocephalic vein. Along its course, multiple tributaries drain into the vertebral vein from the paravertebral plexus and foraminal veins. A catheter and wire are angled medially and superiorly from the junction of the brachiocephalic vein with the internal jugular vein to select the vertebral vein from below.

Roadmaps to each foramen, grouped by common venous drainage pathways. A, Right T5–12. B, Right lumbar. C, Left T9–12 and lumbar. D, Left T5–8. E, Right T1–4. F, Left T1–4. G, Cervical.