Epidural Steroid Injections (ESI)

Performed by Top Pain Management Doctors in San Antonio, Texas


It’s been estimated that between 60-80% of the general population will suffer some type of back pain during their lifetime as a result of spinal problems1, 2. Epidural steroid injections (ESI) are a relatively low risk, and inexpensive, procedure shown to be effective in the treatment of chronic back pain; particularly those cases involving compression or irritation of nervous tissue2.

One of the most common causes of back pain occurs as nerve roots are compressed while traversing channels within the spine; a condition known as a radiculopathy2. The spine has many of these channels through which nervous tissue travels to various regions of the body. For example, the spinal column consists of bones called vertebrae, which are stacked atop one another from the pelvis to the base of the skull, forming a channel to protect the spinal cord7. Another channel, the neural foramen, is formed between facet, or zygopophyseal, joints through which nerve roots exit the spinal cord.

Radiculopathies can occur with a variety of conditions, but most notably with disc herniation and spinal stenosis.

  • A herniated disc describes shifting of some portion of an inter-vertebral disc outside of its natural disc space. Each vertebra is separated by cartilaginous, inter-vertebral discs composed of a tough, fibrous outer layer and filled with a soft, gelatinous inner layer.  These discs support the vertebrae and allow them to shift across one another, facilitating movement of the spine3. Pain is caused if disc material shifts outside of its disc space, and compresses the nearby exiting nerve root from the spinal cord.  Depending upon which nerve root is affected, pain may be felt in the back and legs (lumbar compression) or neck, shoulders, and arms (cervical compression).  Nerve root compression can also cause numbness and/or weakness in some circumstances.  When compression of a lumbar nerve root gives rise to shooting, or stabbing, leg pain, the condition is called sciatica4.A disc can serve as the source of chronic pain, even if it is not directly involved in the compression of nerve roots.  The discs themselves are highly innervated, and irritation to the disc can cause chronic pain much like that associated with nerve root compression; this is termed discogenic pain2, 6.
  • Spinal stenosis describes narrowing of the hollow channels that houses the spinal cord and its nerve roots due to age-related degeneration, spinal tumors, injury or arthritis.  When these channels become narrow, compression of nervous tissue can occur leading to radicular pain5, 7.

 

A condition known as Failed Back Syndrome (FBS) can also cause radiculopathic-like chronic pain.  FBS refers to a condition experienced by patients that have undergone back surgery, in which scar tissue formed following the procedure induces pain through largely unknown mechanisms6.

Studies have shown that ESI’s may provide short-term pain relief for disc herniations, including up to 80% reduction in pain for up to 75% of patients  in one study on sciatica5, 7.  Systematic reviews of medical literature have also shown strong evidence that ESI’s can provide relief for discogenic pain, and chronic pain associated with spinal stenosis6.  In lumbar spondylosis, or bony overgrowth in the spine which can compress adjacent neural tissue, and Piriformis Syndrome, in which leg and hip pain occur  compresses the sciatic nerve due to muscle inflammation, ESI’s have been reported as beneficial for short- and long-term pain relief 4, 5, 7.  Finally, ESI can be used diagnostically to confirm causal locations of pain1. By first using ESI to ensure pain relief, it can confirm a diagnosis before invasive treatment options, such as surgery, are considered.

The Procedure

With ESI’s, a needle is guided to the epidural space near a suspected pain source. The epidural space consists of the area between the outer, protective sheath of the spinal cord and the vertebrae. Once appropriately positioned, a solution can be injected through the needle directly to the epidural space to relieve pain and inflammation. The solution generally consists of an anesthetic, or pain reliever, mixed with a long-acting steroid which acts as an anti-inflammatory2, 6.

During the procedure, the patient lies prone on their abdomen while the injection site is exposed and sterilized with alcohol and iodine1.  The site is then injected with an anesthetic solution to numb the area and prevent discomfort. The remainder of the procedure depends upon the surgical approach used to inject the medication. Three anatomical approaches can be used to administer ESI’s to the spine 2, 4, 8:

  • With the interlaminar approach, an injection is made through the back in between the thin laminar portions of vertebrae which connect the vertebral body to the spinous process, a site of muscle attachment.  This approach allows access to the epidural space such that one injection can spread medication to nerve roots on both sides of the spinal cord.  Studies have shown this approach to be effective for short-term relief of radicular pain due to disc herniation2.
  • With the transforaminal approach, an injection is made into the epidural space from the side through the neural foramen.  This approach requires two injections, as it can only reach one nerve root at a time; however, the transforaminal approach is believed to be more target-specific to the nerve root, and thus possible more effective than other approaches.  Due to the small space in the neural foramen, however, only a small amount of medication can be delivered via injection. Studies have shown strong evidence for the short-term benefit, and moderate evidence for the long-term benefit of using this approach to treat radicular pain2.
  • With the caudal approach, an injection is made into the epidural space through a large structure, the sacral hiatus, found just above the coccyx.  This approach allows for injection of a larger volume of medication.  It is also the preferred approach for patients with disrupted spinal anatomy as a result of previous spinal surgery.  Studies have shown strong evidence that the caudal approach is effective for the relief of radicular pain due to disc herniation and discogenic pain, and moderate evidence that the approach is effective for managing chronic pain associated with FBS and spinal stenosis6.

 

Caudal and interlaminar ESI’s have a higher likelihood for inaccurate needle placement during the injection, since it is less target-specific than the transforaminal approach, but are generally less risky in terms of inadvertent damage to nerve roots2, 7. Regardless of approach, during an ESI procedure, a radiologic technique known as fluoroscopy, a type of real-time x-ray, is used to assist an interventional pain specialist or spinal surgeon in guiding the needle to the proper site for injection2.  Without fluoroscopic guidance, needle misplacement has been reported to occur up to 40% of the time which can lead to complications4.

ESI complications are primarily due to improper needle placement and improper medication injection into vascular tissue, or non-target neural tissue7.  Improper needle placement can lead to unnecessary trauma to nervous and vascular tissue, which can cause headache, neuropathies or bleeding2, 7.  If the injection is inadvertently administered into a vessel, the steroid component of the medication can distribute throughout the rest of the body and cause systemic side effects such as elevated blood sugar (hyperglycemia), elevated blood pressure (hypertension), facial flushing, transient increase in pain, temporary onset of dizziness and/or fainting spells (vasovagal reaction), and bone damage. These complications are considered relatively minor.  More serious complications are very rare, and include spinal cord damage or paralysis2.  Finally, as with any injection procedure, infection is a possible complication of ESI.

In general, ESI is safe; one study found the incidence of complications with ESI to be approximately 9.6%, all of which were minor1, 2, 7. Headache and fainting are perhaps the most common side effects of this procedure.

Conclusions

Epidural steroid injections (ESI) are used to diagnose and treat a variety of painful back conditions, and under some circumstances, delay the need for more invasive surgical treatments4.  ESI is one of the most common treatments for the management chronic back pain, and systematic reviews suggest that, when performed properly, ESI can reduce chronic back pain and disability2.

References/Journal Articles

  1. Epidural Steroid Injection (ESI) – PainDoctor.com
  2. Zhou, Y. (2008). Principles of Pain Management. Bradley: Neurology in Clinical Practice, 5th Ed. MD Consult Web site, Core Collection.
  3. Buenaventura, R.; et al. (2009) Systemtic Review of Therapeutic Lumbar Transforaminal Epidural Steroid Injections. Pain Physician. 12(1). 233-251.
  4. Hansen, J. (2010). Back. Hansen: Netter’s Clinical Anatomy, 2nd Ed. MD Consult Web site, Core Collection.
  5. Williams, K.; Park, A. (2007). Injection Studies. Canale & Beaty: Campbell’s Operative Orthopaedics, 11th Ed. MD Consult Web site, Core Collection.
  6. Isaac, Z.; Wang, D. (2008). Lumbar Spinal Stenosis. Frontera: Essentals of Physical Medicine and Rehabilitation, 2nd Ed. MD Consult Web site, Core Collection.
  7. Conn, A.; et al. (2009) Systematic Review of Caudal Epidural Injections in the Management of Chronic Low Back Pain. Pain Physician. 12(1). 109-135.
  8. Amsterdam, J., Kilgore, K. (2009). Lumbar Spinal Stenosis. Bradley: Roberts: Clinical Procedures in Emergency Medicine, 5th Ed. MD Consult Web site, Core Collection.
  9. Parr, A.; et al. (2009) Lumbar Interlaminar Epidural Injections in Managing Chronic Low Back and Lower Extremity Pain: A Systematic Review. Pain Physician. 12(1). 163-188.