The goal of an epidural steroid injection is to place this medication near the area of injury or pathology within the spine. The steroid medication reverses the effect of pain-producing inflammatory compounds produced by the body, thereby easing pain and allowing for improved function. The most common use of epidural steroid injection is for spinal nerve irritation, commonly referred to as radiculopathy or, in the lower back, as sciatica. Epidural injections are also commonly used to treat intervertebral disc pain, spinal arthritis, spinal fractures, post-surgical pain, tumor-related inflammation and post-herpetic neuralgia. The injections can be performed on any level of the spine. Three distinct techniques are commonly used and are described below:
Interlaminar Epidural Injections: In this technique, an x-ray (fluroscopy) is used to guide a needle into the posterior epidural space.
Transforaminal Epidural Injections: This technique represents a very precise, x-ray controlled injection of a small volume of medication into the anterior epidural space and the exiting spinal nerve sheath. It is a useful technique for precisely diagnosing the specific level of pain generation, as well as treating pain of disc or spinal nerve origin. When making a diagnosis, the suspected areas of pain generation are located on x-ray and a small needle is placed into each neural foramen (the spinal opening through which the spinal nerve exits). Each needle is then injected with a small amount of contrast and the appropriate spinal nerve and proximal epidural space is observed on the x-ray monitor. The resulting contrast spread, called an epidurogram, can give valuable information regarding the anatomy at the injected level. Additionally, the patient may feel a paresthesia, or tingling sensation, in the area of the body supplied by the injected spinal nerve. If this paresthesia is in the same location as the patient's pain, it can be deduced that this spinal nerve is contributing to the patient's pain symptoms. Furthermore, the injection of a small amount of local anesthetic should eliminate the pain for a short time, further supporting the diagnosis. The injected steroid acts to decrease inflammation at the specific area of injection, thereby providing analgesia and allowing for increased function. Several studies have confirmed that transforaminal epidural steroid injections are highly effective in treating radicular pain and can prevent surgery.
Caudal Epidural Injections: This is a technique that accesses the epidural space near the tail bone. It is used for pathology in the lower spine, such as pain in the coccyx or tail bone, or to atraumatically access the epidural space in the patient with low back pain and a history of previous lumbar surgery. By entering below the area of previous surgery, scars and surgically altered anatomy can be avoided. This is performed with X-ray guidance and contrast injection to assure correct needle placement. Typically, relatively large volumes of medication are injected into the caudal space, ten to fifteen ml, to assure that the medication reaches the areas of pathology. Another advantage to the caudal approach is the tendency for the injected medication to pass into the anterior epidural space, the area adjacent to the spinal nerves and discs.