What are Epidural Steroid Injections?
Epidural steroid injections (ESI) have been utilized for many years to diagnose and treat spinal pain. One of the first reported uses of an epidural injection was in the 1920s for the treatment of back pain and sciatica (1, 2). In 1960, direct epidural injections of corticosteroids were used for pain in the lower back and sciatica (3, 4). ESI is commonly used for spinal stenosis, degenerative disc disease, herniated disc, sciatica, and radiculopathy. Cervical (neck) and thoracic (chest) ESI can also be used for post-herpetic neuralgia, which is nerve pain experienced after an episode of shingles. ESI is used when a patient’s pain is unresponsive to oral pain medications. However, ESI are for symptomatic relief only, this will not resolve the underlying cause of the pain. ESI is an injection of a corticosteroid such as betamethasone into the patient’s back at the level of the spine where the pain is located. The corticosteroids are an anti-inflammatory, so inflammation and swelling are reduced, thereby decreasing pain. The corticosteroid is mixed with a local anesthetic like bupivacaine which will provide immediate short-term pain relief which lasts for several hours. The corticosteroid will begin to work 3-5 days after the injection, and effects can last weeks to several months. The injections can be given in a series of three or be used as one individual treatment. If given in a series, the injections must be spaced out at least two weeks apart due to the lasting systemic effects of the corticosteroids. Generally no more than three injections can be given in a six month period. If a patient has not responded after three injections, alternative therapies should be investigated (5).
ESI Clinical Trial Papers
- Cohen et al. 2012
- Carette et al. 1997
- Arden et al. 2005
- Ghahreman et al. 2010
- Riew et al. 2000
- Sayegh et al. 2009
- Kraemer et al. 1997
- Meadeb et al. 2001
- Vad et al. 2002
- Wilson-MacDonald et al. 2005
- Nam & Park 2011
- Dilke et al. 1973
Relevant Anatomy for Procedure
The corticosteroid is injected into the epidural space in the back. The epidural space is the outermost portion of the spinal canal. The spinal canal is formed by the vertebrae or back bones. The epidural space is within this canal just outside of the dura mater, the outermost layer of the spinal canal and the inside surface of the bone. The dura mater encloses another layer called the arachnoid mater, and the pia mater is the innermost layer of the spinal canal. Within the pia mater is the spinal cord and cerebral spinal fluid. The epidural space runs the length of the spinal column. It is considered a potential space which means that is does not normally exist. The anterior and posterior spinal nerve roots originating from the spinal cord pass through the epidural space to the intervertebral foramen (a portion of the vertebra) to form segmental nerves. It is these nerves that are generally the target of ESIs; by injecting a corticosteroid into the epidural space (which these nerves pass through), inflammation of the nerves can be decreased. It must be noted, however, the medication is injected around the nerve, not into the nerve. In order to access the epidural space from the back, there are several layers the needle must pass through. The outermost layer is the skin, followed by the subcutaneous tissue (fat and connective tissue), the paraspinal muscles(if using a paramedian approach) or the interspinous ligament (if using midline approach), and then lastly the ligamentum flavum; the last layer before the epidural space (6). There are different ways to approach the epidural space which are described in the next section.
Description of Procedure
There are three different techniques to perform an epidural steroid injection, known as interlaminar, transforaminal, and caudal approaches. The decision on which technique to use is determined by the location and cause of pain. Epidural steroid injections are performed as outpatient procedure and take approximately 10-15 minutes. The patient will lie on their stomach or on their side on the procedure table. The physician will first numb the area with a local anesthetic such as lidocaine. Once the area is numb, the physician will insert the needle for the epidural injection. Most physicians now use fluoroscopy, a type of x-ray, to help guide the needle into the correct location. The x-ray machine looks like a large C and will be placed over the patient while on the procedure table. Once the physician determines the needle is in the correct location, the physician will inject a dye or contrast, and then view the contrast using fluoroscopy to verify the correct location. If the physician is satisfied with the location of the needle, the corticosteroid mixed with an anesthetic will then be injected. The needle is then removed and the procedure is complete. Generally, a small adhesive bandage will be placed over the site of the needle insertion (6, 7).
- Interlaminar Approach: With this approach, the needle is inserted in the middle of the back between the spinous processes of the vertebrae. The spinous processes are the posterior portion of the back bones, or the bony prominence felt when bending over. The corticosteroid and anesthetic that is injected will affect the nerve roots on both the left and right side of the spine at the level the medication was injected (6, 7).
- Transforaminal Approach: This technique is performed with the patient lying on their stomach. The needle is placed in the neuroforamen, which is the opening at the side of the spine where a nerve root exits. This approach is ideal for nerve root compression because it allows the needles to be placed closer to the inflamed or irritated nerve root as opposed to using the interlaminar approach. Ackerman and Ahmad (2007) found the transforminal approach to be more effective than the interlaminar or caudal approach for the treatment of disc herniations and radicular pain in the L5-S1 location (8). This approach treats one side at a time, so if the patient has an irritated or compressed nerve root on both sides, two injections may be needed, or a different approach can be utilized. This technique may also be used for people who have previously had spine surgery with surgical rods, screws, or pins in their spine. This approach helps the physician avoid these implanted surgical devices (6).
- Caudal Approach: The caudal approach is used exclusively for sacral injections and is utilized for low back pain and sciatica. The sacrum is the lowest portion of the spine and connects the spine to the hip bones. The needle is inserted through a small opening in the sacrum called the sacral hiatus, into the epidural space (6).
Benefits of Epidural Steroid Injections
The obvious benefit of an ESI is pain relief, but ESIs can actually shorten the length of the disease process by providing symptomatic relief, improved quality of life, and possible reduction in the use of oral pain medications (9, 10).
Botwin et al (2002), followed 34 patients that received transforaminal epidural steroid injections for sciatica caused by lumbar spinal stenosis (11). At one year follow-up, 75% of patients had greater than 50% reduction in their pain rating, 64% had improved their walking duration, and 57% had improved their tolerance to standing (11). Numerous studies have been performed regarding the efficacy of transforminal ESIs for chronic radicular pain; however, many of these studies are case reports or lack placebo groups, which make these studies less valuable. However, a systematic review of studies published show a strong recommendation for transforminal epidural injections for chronic radicular pain. It should be noted that this recommendation may change when better studies are available (12).
A study performed by Sayegh and colleagues (2009) found 72.1% of patients had symptom improvement following a caudal epidural injection (13). Patients that received an injection of an anesthetic and a corticosteroid experienced faster relief during the first week after the injection as compared with patients that only received an injection of an anesthetic (13). A systemic review suggests there is strong evidence for caudal ESIs for short-term relief, and moderate evidence for long-term relief for patients with chronic low back pain from radiculopathy and post-lumbar laminectomy syndrome (14).
A review of studies published revealed strong evidence for interlaminar lumbar epidural steroid injections for short-term pain relief and a limited amount of evidence for long term pain relief (15). Another review endorsed strong recommendation for the use of interlaminar lumber epidural steroid injections for the use of short term pain relief in patients with disc herniation causing nerve root compression or inflammation (16).
For cervical spine (neck region) injections, there is a moderate amount of evidence suggesting the efficacy of cervical transforaminal ESIs for managing cervical nerve root pain (15).
Many of the studies reviewing the effectiveness of ESIs are in patients with radiculopathy (nerve root) pain. This is difficult to translate to other conditions that ESIs can be used for. Patient response to ESI is related to the underlying cause of the pain. Acute radicular pain from a disc herniation has been found to have a better response rate than patients with pain from lumbar spinal stenosis. However, each patient responds differently and many patients with stenosis respond well (5, 6).
Risks of Epidural Steroid Injections
ESI is a relatively safe procedure. Complications are infrequent but have been reported to be epidural hematoma, Cushing’s syndrome, temporary paralysis, epidural abscess (an infection at the site of the injection), anaphylaxis (a severe allergic reaction), nerve root injury, and a spinal headache if the dura mater is punctured (7, 17, 18). The most immediate adverse reaction during an ESI is a vasovagal reaction (7). This is when the blood vessels in your body vasodilate or relax causing your blood pressure to decrease. Often, people feel lightheaded and may even faint with a vasovagal reaction, however, this reaction is temporary. A retrospective study of 207 patients that received transforaminal epidural steroid injections found 3.1% of patients experienced a transient non-positional headache that resolved within 24 hours, 2.4% had an increase in back pain, 1.2% had facial flushing, 0.6% experienced increased leg pain, and 0.3% had a vasovagal reaction (19). As seen in this study, out of 207 patients, only a small percentage of patients experienced an adverse reaction after a transforminal ESI.
Patients with the following issues should not receive an ESI: uncontrolled diabetes or heart disease, active infection, bleeding disorder, or on blood thinning medications i.e. Coumadin (warfarin) (6).
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