Spinal Venous Plexus¶
Definition¶
The spinal venous plexus (Batson plexus) is an extensive, valveless network of veins that drains the vertebral column, spinal cord, and surrounding structures. Its valveless nature allows bidirectional flow, which is clinically significant as a route for hematogenous metastatic spread to the vertebral bodies.
Anatomy¶
Components¶
The spinal venous plexus is divided into internal and external components:
Internal vertebral venous plexus (epidural veins):
- Located within the epidural space between the dura and the vertebral canal walls
- Consists of anterior and posterior longitudinal channels connected by transverse anastomoses
- The anterior internal plexus runs along the posterior surface of the vertebral bodies, on either side of the posterior longitudinal ligament
- The posterior internal plexus runs along the anterior surface of the laminae and ligamenta flava
- These are thin-walled, valveless veins embedded in epidural fat
External vertebral venous plexus:
- Located on the external surfaces of the vertebral column
- Anterior external plexus on the anterior vertebral body surface
- Posterior external plexus surrounding the spinous processes and laminae
Connecting Veins¶
- Basivertebral veins — drain the vertebral body marrow through a large foramen on the posterior vertebral body surface into the anterior internal plexus
- Intervertebral veins — exit through the neural foramina, connecting the internal plexus to the segmental veins (intercostal, lumbar, lateral sacral)
- Radicular veins — small veins draining the nerve roots
Batson Plexus — Clinical Significance¶
Oscar Batson described this valveless venous network in 1940, noting that increased intra-abdominal or intrathoracic pressure (coughing, straining, Valsalva) can reverse flow in these veins, directing venous blood from the pelvis, abdomen, and thorax into the vertebral venous plexus. This provides a direct route for metastatic tumor cells to reach the vertebral bodies without passing through the heart or lungs.
Clinical Pearl
The Batson plexus explains why vertebral metastases are so common, particularly from cancers of the prostate, breast, lung, kidney, and thyroid. Prostate and breast cancers have a particular predilection for vertebral metastases because venous drainage from the pelvis and chest communicates directly with the vertebral venous plexus through valveless channels. This also explains why vertebral metastases can occur without concurrent pulmonary metastases.
Imaging Findings¶
CT¶
- Epidural veins are not normally conspicuous on routine CT
- Dilated epidural veins may be seen as enhancing structures in the epidural space, simulating disc herniation or epidural mass
- Basivertebral venous channel seen as a Y-shaped lucency in the posterior vertebral body on axial images
MRI¶
| Finding | Appearance |
|---|---|
| Normal epidural veins | Small flow voids in epidural fat on T2; enhance on post-contrast T1 |
| Dilated epidural veins | Prominent flow voids or enhancing structures in the anterior epidural space; may mimic disc herniation |
| Basivertebral vein | Focal bright signal on T2 in the posterior vertebral body (slow flow); enhances on post-contrast imaging |
| Epidural venous engorgement | Seen with IVC obstruction, pregnancy, or SVC syndrome; prominent flow voids throughout the epidural space |
| Normal CSF pulsation artifact | Caused by the cardiac-driven oscillatory motion of cerebrospinal fluid within the spinal canal; Can stimulate or mimick the appearance of enlarged vessels such as seen in in cases of CSF-venous vistulas |
Key MRI Finding
Dilated anterior epidural veins can mimic disc herniation on axial MRI. The key distinguishing feature is that epidural veins show prominent enhancement on post-contrast images and may demonstrate flow voids on T2, whereas disc herniations have signal similar to the parent disc and do not enhance (except at the periphery in chronic herniations).
Key Points¶
- The spinal venous plexus is a valveless network allowing bidirectional flow
- Batson plexus provides a direct route for metastatic spread to the vertebral bodies
- The internal plexus lies in the epidural space; the external plexus surrounds the vertebral column
- Valveless connections explain vertebral metastases without pulmonary involvement
- Dilated epidural veins can mimic disc herniation on MRI — post-contrast imaging helps differentiate
- Basivertebral veins drain marrow through the posterior vertebral body
References¶
- Nathoo N, Caris EC, Wiener JA, Mendel E. History of the vertebral venous plexus and the significant contributions of Breschet and Batson. Neurosurgery. 2011;69(5):1007-1014. PMID: 21654535. https://pubmed.ncbi.nlm.nih.gov/21654535/
- Brook RC, Tung K, Oeppen R. Batson's plexus and retrograde venous spread of malignancy — a pictorial review. Cancer Imaging. 2014;14(Suppl 1):P40. PMCID: PMC4242660. https://pmc.ncbi.nlm.nih.gov/articles/PMC4242660/
- Geldof AA. Models for cancer skeletal metastasis: a reappraisal of Batson's plexus. Anticancer Res. 1997;17(3A):1535-1539. PMID: 9179192. https://pubmed.ncbi.nlm.nih.gov/9179192/
- Nishijima Y, Uchida K, Koiso K, Nemoto R. Clinical significance of the vertebral vein in prostate cancer metastasis. Adv Exp Med Biol. 1992;324:93-100. PMID: 1492629. https://pubmed.ncbi.nlm.nih.gov/1492629/
- Radiopaedia. Vertebral venous plexus. https://radiopaedia.org/articles/vertebral-venous-plexus-1