The diploic venous system: surgical anatomy and neurosurgical implications

History of the vertebral venous plexus and the significant contributions of Breschet and Batson

Before the 18th century, the vertebral venous plexus (VVP) received scant mention, had no clinical relevance, and was largely ignored by anatomists, most likely because of its location and nondistensible nature. Gilbert Breschet in 1819 provided the first detailed anatomic description of the VVP, describing it as a large plexiform valveless network of vertebral veins consisting of 3 interconnecting divisions and spanning the entire spinal column with connections to the cranial dural sinuses distributed in a longitudinal pattern, running parallel to and communicating with the venae cavae, and having multiple interconnections. More than a century passed before any work of significance on the VVP was noted. In 1940, Oscar V. Batson reported the true functionality of the VVP by proving the continuity of the prostatic venous plexus with the VVP and proposed this route as the most plausible explanation for the distribution of prostate metastatic disease. With his seminal work, Batson reclassified the human venous system to consist of the caval, pulmonary, portal, and vertebral divisions. Further advances in imaging technology confirmed Batson's results. Today, the VVP is considered part of the cerebrospinal venous system, which is regarded as a unique, large-capacitance, valveless plexiform venous network in which flow is bidirectional that plays an important role in the regulation of intracranial pressure with changes in posture and in venous outflow from the brain, whereas in disease states, it provides a potential route for the spread of tumor, infection, or emboli.

A case of intraosseous dural arteriovenous fistulas involving diploic vein treated with transarterial onyx embolization

Intracranial dural arteriovenous fistulas (DAVFs) are abnormal arteriovenous connections that lie within the dura. Intraosseous DAVFs involving diploic venous system are extremely rare. A 46-year-old woman presented with headache and right pulsatile tinnitus for three weeks. The tinnitus started after yelling. Digital subtraction angiography revealed DAVF within the basal portion of right parietal bone along the middle meningeal artery (MMA) groove. The fistula was fed by frontal branch of right MMA and drained into right transverse sigmoid sinus junction through dilated middle meningeal vein. The intraosseous DAVF involving diploic vein was successfully obliterated with Onyx embolization via transarterial route.

Developmental and circulatory profile of the diploic veins

To examine the development of the diploic veins in the calvarium, FITC-dextran was injected into the tail vein. The total area of the diploic veins showed a continuous, age-dependent development. We also measured the red blood cell (RBC) velocities in the diploic veins using an in vivo imaging technique and revealed RBCs with a significantly high velocity and unidirectional characteristics at the entrance route. The route passed from the basal periosteum of the cranial bone via the dura mater and into the diploic veins. Our findings indicate the existence of communications between intra- and extra-cranial circulation.