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.
First, your back will be cleaned with an antiseptic solution and a sterile drape will be placed. Next, the doctor will identify the area he or she will inject using an x-ray machine. Once the location is identified, you will feel a pinch and a burn as numbing medicine is injected into that spot using a fine needle. After the numbing medicine takes effect, you should only feel pressure as the doctor places an epidural needle into the correct position using multiple x-rays. Once the needle is in the epidural space, you may feel pressure or even worsening of your typical pain as the doctor injects the medication.
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.