Role of Epidural and Radicular Veins in Chronic Back Pain and Radiculopathy

Abstract

Although the pattern and major components of the human medullary arterial supply were widely known by the end of the nineteenth century, the details of the associated venous circulation were generally ignored. Despite Brechet’s (1) quite accurate description and later depiction of the complexity of the spinal venous system, published in 1835 (Fig.1), the ubiquity and variability of its ramifications evidently discouraged further consideration beyond the comprehension that the veins collectively served as collateral channels to the caval and azygos systems. Another factor that may have contributed to the general disregard of the anatomical particulars of these channels may have been related to their structural delicacy. The thinness and transparency of their walls render them almost invisible during conventional cadaver dissections unless they show postmortem evidence of congestion or are specifically filled with a contrast medium. Clemens (2) noted that these vessels were quite pliable, which permitted considerable distension under collateral load. Thus, the Queckenstedt maneuver, which tests the patency of the spinal subarachnoid space by compression of the jugular or intra-abdominal veins, causes an increase in cerebrospinal fluid (CSF) pressure by an external compression from the expansion of the collaterally loaded epidural plexus. Clemens also postulated that a passive congestion of the spinal cord was prevented by minute valves in the proximal sources of the radicular veins that drain the spinal cord, a unique situation considering that none of the other sinus veins possess valves.