The vertebral venous plexus (Batson plexus) is an extensive valveless venous network surrounding the vertebral column, comprising the internal plexus within the spinal canal and the external plexus around the vertebrae. The plexus communicates with the azygos system, the IVC, the caval veins, the pelvic veins, the segmental intercostal veins, and the basilar skull sinuses. The absence of valves allows bidirectional flow depending on pressure gradients.
Batson plexus provides a valveless route for haematogenous spread of cancer from pelvic organs (prostate, bladder, uterus) and abdominal organs to the spine, bypassing the caval filter. This explains the predilection of prostatic cancer for vertebral metastasis. Elevated intra-abdominal pressure (Valsalva manoeuvre, straining) retrograde forces blood from pelvic and abdominal veins back through Batson plexus into the epidural and paravertebral spaces, contributing to discogenic and radicular pain fluctuation. The epidural venous plexus component is the target for epidural blood patches in spinal headache.
Prostate, breast, thyroid, lung, and renal cancers spread to the vertebral column via retrograde flow through the valveless Batson plexus, bypassing hepatic and pulmonary capillary filters that would normally trap circulating tumour cells, explaining why isolated vertebral metastases occur without lung or liver involvement.
Spontaneous or anticoagulant-related bleeding from the epidural venous plexus within the spinal canal produces an acute epidural haematoma that compresses the cord or cauda equina, presenting as back pain with rapidly progressive neurological deficit requiring emergency MRI and surgical decompression.
