collateral veins are produced by your body when it is not getting sufficient circulation from a part of the body. If a part of your body is not returning blood back to the heart from a specific vein, your body will grow veins around that area to assist in circulating the blood. Unfortunately these veins are usually thinner and less organized than the original venous structures. Spider veins are examples of collateral veins.
We saw several small collateral veins surrounding Jeff's left jugular vein. His left jugular was 100% occluded, and these smaller spidery veins were trying to get his blood around the blockage. Some doctors will claim that collateral veins provide sufficient drainage to an area, and that jugular vein blockage will be dealt with by the body. Be prepared to hear this when discussing jugular vein stenosis. However collateral veins are not able to transit the blood back to the heart as efficiently as the original parent vein. They are fragile and prone to distension and leakage. This can be seen by the eye in chronic venous insufficiency in the leg, where red blood cells and fluid are deposited into the tissue by overwhelmed collateral drainage veins.
Once Jeff's left jugular vein was opened, these small over-stressed veins became invisible. The stented and working jugular removed any issues of reflux into the brain, as well as any leakage into the surrounding tissue of his neck. Jeff has a large lesion on his cervical spine where this collateral drainage was occurring. It will be interesting to see if the lesion shows signs of healing, now that the leakage in this area has been removed.
Since the azygos vein runs parallel to the spine, it is easy to understand how collateral veins (which would form along the spine to circumvent blockage in that area) could easily leak into the spinal column and cause lesions.
Collateral veins do provide a means to get deoxygenated blood back to the heart...however they can lead to reflux and fluid deposition. If a doctor tells you that you don't need a functioning jugular or azygos vein, and that collateral drainage should be sufficient, you need to understand why they are wrong. This will be one of many arguments raised against CCSVI. Be prepared...