There are two ways in which epidural steroid injections may work, however, there is little scientific evidence supporting either of these theories. The first belief is that some leg or arm pain involves the inflammation of one or more of the nerves, their covering, or their roots, in the back. The injection of steroids into the part of the spinal column called the epidural space is thought to aid in reducing this inflammation. The other belief is that the corticosteroid acts like a local anesthetic and reduces pain to allow the body to begin the process of repairing itself.
This is a rare complication that may occur if a small hole is made in the fibrous sac and does not close up after the needle puncture. These small holes are only made in less than 1% of epidural injections and usually heal on their own. The spinal fluid inside can leak out, and when severe, the brain loses the cushioning effect of the fluid, which causes a severe headache when you sit or stand. These types of headaches occur typically about 2-3 days after the procedure and are positional - they come on when you sit or stand and go away when you lie down. If you do develop a spinal headache, it is OK to treat yourself. As long as you do not feel ill and have no fever and the headache goes away when you lay down, you may treat yourself with 24 hours of bed rest with bathroom privileges while drinking plenty of fluids. This almost always works. If it does not, contact the radiologist who performed the procedure or your referring physician. A procedure (called an epidural blood patch) can be performed in the hospital that has a very high success rate in treating spinal headaches.