Venous congestion as a central mechanism of radiculopathies.

Compression of roots/nerves can disrupt some of their functions, but does not necessarily cause pain. This is illustrated by the frequency of nearly asymptomatic spinal stenosis or disc herniations. In fact, pain of radiculopathies (and nerve entrapments) may mostly be the consequence of intraneural oedema induced by microscopical venous stasis around roots/spinal ganglia (or nerves) not or poorly shown by imaging. This narrative review first lists arguments for a role of congestion of vasa-nervorum in the pathophysiology of radiculopathies, including those induced by disc herniation and spinal stenosis, but also other sources of overpressures in spinal venous plexuses (pregnancy, vena cava atresia and thrombosis, portal hypertension, epidural varices, arterio-venous fistula, vertebral hemangioma or hemangioblastoma). It also details sources of venous congestion around nerves outside the spine, from pelvis (May-Thurner syndrome, Nut-cracker syndrome) to buttocks (superior and inferior gluteal veins), and even thighs and legs. A better recognition of a preeminent role of venous congestion in radiculopathies, plexopathies, and nerve entrapments, should have major consequences: (i) discard the dogma that compression is mandatory to induce root/nerve suffering, since root/nerve adherences in two locations can impair blood flow in vasa-nervorum through root/nerve stretching; (ii) implementation of sensitive techniques to visualise impingement of blood flow around or within roots and nerves; (iii) better prevention of roots/nerves adherence, or arachnoiditis induced by extravascular fibrin deposition secondary to venous stasis.; (iv) optimizing treatments dampening clot formation and/or extravascular fibrin leakage in the intradural/peridural spaces, or around roots/nerves, like guided injection of tissue plasminogen activator.