Epidural injections are often used to treat radicular pain, also called sciatica , which is pain that radiates from the site of a pinched nerve in the low back to the area of the body aligned with that nerve, such as the back of the leg or into the foot. Inflammatory chemicals (. substance P, PLA2, arachidonic acid, TNF-α, IL-1, and prostaglandin E2) and immunologic mediators can generate pain and are associated with common back problems such as lumbar disc herniation or facet joint arthritis . These conditions, as well as many others, provoke inflammation that in turn can cause significant nerve root irritation and swelling.
A dural puncture, or "wet tap," is perhaps the most common complication from an ESI. This complication only occurs in to 5 percent of all injections. The result of a dural puncture is usually a spinal headache and nausea. A spinal headache occurs when the puncture in the spinal sac fails to seal itself off. This allows the spinal fluid to continue to leak out and lowers the spinal fluid pressure in the brain. When sitting or standing, the headache and nausea are much worse because the spinal fluid pressure is lower at the top (near your head) than at the bottom of the spine. The headache usually goes away when you lie down with your feet higher than your head.