A venous fistula is an abnormal connection between a vein and another structure, typically an artery or, in the case of cerebrospinal fluid (CSF) leaks, the subarachnoid space.

🩸 General Definition:
A venous fistula is an unnatural, direct communication that allows fluid to bypass normal circulation and flow into a vein from a source where it shouldn’t—such as an artery or the cerebrospinal fluid space.