To provide a better understanding of the injection procedure and the region that the medication is administered, the spinal region will first be briefly described. There are a vast number of nerves that run along the spinal cord. The nerves extend throughout the entire body and are protected by cerebrospinal fluid (CSF). The spinal cord is also stabilized by a tough membrane within the spinal column. The area that is directly outside of the membrane is referred to as the epidural space. The roots of damaged, irritated, or inflamed nerves, which are the targets for the steroid injections, are located in the epidural space.
With a transforaminal epidural steroid injection (ESI), often referred to as a 'nerve block', the needle is placed alongside the nerve as it exits the spine, and medication is placed into the 'nerve sleeve'. The medication then travels up the sleeve and into the epidural space from the side. This allows for a more concentrated delivery of steroid into one affected area (usually one segment and one side). Transforaminal ESIs can also be modified slightly to allow for more specific coverage of a single nerve and can provide diagnostic benefit, in addition to improved pain and function.