Epidural steroid injections for spinal pain

Author: Dr Sibel Demir-Deviren University of California San Francisco 2008-07-10

Introduction

Spinal pain is the most common of all chronic pain disorders. The number of individuals that have, at some point in their life, experienced spinal pain has been reported as 54 to 80%. After the initial painful episode, the prevalence of persistent low back and neck pain ranges from 26 to 75%.

Axial (neck or low back pain) and radicular pain (radiating pain to arm or leg) may arise from any anatomic structure capable of transmitting pain (the pain generator).  Pain generators include vertebral discs, nerve roots, dura (the outer layer of membrane surrounding the brain and spinal cord), muscles, fascia (soft, connective tissue), ligaments, and facet joints. Injury to any of these structures results in the release of inflammatory mediators. Epidural injection of steroid (cortisone, corticosteroid) is one of the most commonly used interventions to decrease the inflammation in managing persistent spinal pain.

Historically, the epidural steroid injection is the first-line invasive therapeutic procedure of choice in patients with spinal pain. In 1901, the first independent reports on the use of caudal epidural injections in the treatment of lumbar nerve root compression were published. The first reportedly successful use of lumbar epidural injections as a treatment for sciatica was in 1909. In 1930, a success rate of 61% was reported for the treatment of sciatica following the caudal injection of large volumes of local anesthetic and saline. The first reported use of epidural steroids was in 1957 as a treatment for radicular leg pain.

Mechanisms of Action

Patho-anatomic evidence shows that spinal discs can produce pain in the neck and upper extremities, thoracic spine, chest and abdominal walls, low back, and lower extremities. Disc related pain is caused by disc degeneration, disc herniation, or by biochemical effects including inflammation. Traditionally, compression of nerve roots by disc herniation has been regarded as the cause of radiating pain to arm or leg, but during the past decade, the pivotal role of multiple causes has been implicated.

Chemical mediators, such as phospholipase A_2, play integral roles in the development of pain when released from a herniated disc. In addition, prostaglandins and leukotrienes have been demonstrated to sensitize pain receptors and enhance pain generation. Steroids inhibit phospholipase A₂, thereby limiting the formation of prostaglandins and leukotrienes.

Both mechanical compression and chemical irritation of nerve roots have been shown to cause nerve root inflammation. Injected steroids possess potent anti-inflammatory effects that are more pronounced when administered at the site of the pain generation.

In addition, one mechanism by which injured nerves cause chronic pain is by generating abnormal (ectopic) discharges in nerve fibers. When injected locally, steroids have been shown to prevent ectopic discharge from injured nerves and suppress the ongoing neural activity, which also contributes to pain.

Purported advantages of epidural steroids over oral delivery include direct deposition of the drug into the affected area, use of much smaller dosages with fewer side effects, and longer duration of pain relief.

Anatomic Consideration

The epidural space lies between bony-ligamentous structure lining the vertebral canal and the dural membrane surrounding the spinal cord and the nerve roots. Each nerve root exits the spine via an intervertebral foramen (canal/hole).

There are several different ways to access the lumbar (low back) epidural space to deliver steroids:            
         1) Interlaminar epidural steroid injection
         2) Caudal epidural steroid injection
         3) Transforaminal epidural steroid injection

There are two different modes of access used to reach the cervical (neck) or thoracic (upper and lower back) epidural spaces:
            1) Interlaminar epidural steroid injection
          2) Transforaminal epidural steroid injection

Is Fluoroscopy (C-Arm, x-ray machine) medically necessary?

Historically, the epidural space was accessed from the back through the interlaminar approach or inferiorly through the caudal approach, often without the use of fluoroscopy, an imaging technique, similar to an x-ray, used by physicians to obtain real-time images of internal structures. A major criticism of these blind approaches (without fluoroscopy) is lack of target specificity. Even when performed by experienced clinicians, blind epidural injections result in incorrect placement of the needle 25 to 40 % of the time. Injection of contrast medium (substance used to make structures more visible) is also strongly recommended to confirm correct needle placement within the epidural space. For these reasons, blind epidural injections have been abandoned in favor of a fluoroscopically guided approach.

1) Interlaminar Epidural Steroid Injections (ESI)

The interlaminar epidural approach involves insertion of an epidural needle midway between two adjacent vertebrae. For lumbar and thoracic interlaminar epidural injections, 6 to 8 ml of steroid, local anesthetic and sterile saline injection mixture is recommended. For cervical interlaminar epidural injections, 4 to 6 ml of total volume of steroid, local anesthetic, and sterile saline mixture is used.

The clinical evidence supporting use of interlaminar ESI is conflicting. Almost half of the studies report positive results and half report negative results. Based on a recent review, the use of interlaminar ESI to control lumbar radiating pain shows that interlaminar ESI provide good short term relief (6 weeks) but limited long term relief (6-12 months). In the management of cervical radiating pain with cervical interlaminar ESI, the evidence is moderate for both short and long term improvement.

2) Caudal Epidural Steroid Injections

The caudal epidural approach involves insertion of a spinal needle into the sacral hiatus, a hole located just above the tailbone. Caudal epidural injections require larger volumes of injected fluids than lumbar, thoracic and cervical ESI. Depending on the proposed pain generator, 10 to 15 ml of injection mixtures is recommended. This will often require dilution of steroid with sterile saline and local anesthetic.

3) Transforaminal Epidural Steroid Injections (TFE)

Over the last 10 years, the wide variations in reported success rates with interlaminar ESI have generated intense interest in the use of transforaminal epidural injections (TFE). The transforaminal epidural steroid injection involves insertion of a spinal needle into the upper portion of an intervertebral foramen (hole) where the nerve root is exiting the spine. The medication mixture goes to epidural space and nerve root sleeve which is responsible from the patient's pain.  TFE require 2 ml of steroid and local anesthetic mixture for the lumbar and thoracic spine. For the cervical spine 1 to 1.5 ml of steroid and local anesthetic mixture is recommended.

TFE provides several advantages over traditional interlaminar and caudal ESI. These include direct deposition of steroid at the level and side of the pain generator, having a greater percentage of injected steroid reach the ventral epidural space (the site of most inflammation), and dramatic reduction in or even elimination of the risk of spinal headache. Based on multiple studies, TFE is more effective than interlaminar and caudal ESI. Because of its advantages, TFE under fluoroscopic guidance has emerged as the preferred approach to deliver steroids to the epidural space. Forty to eighty five percent of patients have successful long-term (more than 3 months) pain relief. Both the duration and the amount of pain relief depend on the pain generator or generators, diagnosis, severity of the problem, and the patients’ functional limitations. The best candidates for TFE are patients with acute radiating pain to arm or leg whose symptoms correlate with imaging studies or electrodiagnostic testing. The response to TFE is also helpful to find out the potential success rate of surgery, if needed. Patients who had 70-80% relief from the TFE are shown to have greater than 95% success in achieving average of 90% pain relief after the surgery.
 
4) Selective Nerve Root Blocks (SNRB)

Although the terms TFE and SNRB are sometimes used interchangeably, they are separate procedures with minimal differences in the needle location. SNRB is often overlooked as a diagnostic tool and as a potential temporizing pain relief therapy. SNRB delivers a low volume (1 – 1.5 ml) of concentrated medication (mixture of steroid and local anesthetic) directly into the nerve root sleeve in question.

SNRB is most appropriately used in patients with radiating pain. In many instances, the source of the radiating pain can be diagnosed with imaging studies and careful examination. However, there are patients with radiating symptoms for whom results of an examination may be equivocal and an imaging study may demonstrate nonspecific findings at one or more levels. When careful evaluation and imaging studies do not make diagnosis clear in patients with radicular or radicular like symptoms, SNRB is considered to be a pivotal diagnostic test in making a determination for surgery. This test uses pain relief as a diagnostic endpoint to detect the nerve root responsible from the symptoms. In patients with multilevel imaging abnormalities, or in the case of postoperative patient, SNRB can help guide the surgeon to the proper level or levels where the pain is originating. This information may help to limit the extent of surgery or in some cases may prevent surgery.

Medications, Dose and Frequency

Commonly used steroid preparations include betamethasone, dexamethasone, triamcinolone and methylprednisolone. Of these, betamethasone and dexamethasone have the strongest anti-inflammatory effects.

Unfortunately, there is no consensus regarding the most effective medication, dose, volume, or frequency. It is suggested that patients receive no more than 12 mg of betamethasone (or other corticosteroid equivalent) at one time and no more than four steroid containing injections in any one year.

Betamethasone is an equal mixture of two betamethasone salts and allows for both immediate and delayed steroid responses. Immediate acting betamethasone acts within hours, whereas the delayed acting salt is slowly absorbed over approximately two weeks. Typically, epidural injection doses vary with number of injections the patient is getting at the same time and range from one to three ml (6-18 mg). Based on our clinical experience, 18 mg betamethasone is most likely to cause systemic side effects (see below). Therefore in our practice, we avoid to use more than 12 mg betamethasone in one set of injections.

Dexamethasone has a rapid onset and long duration of action. Dexamethasone is the only nonparticulate corticosteroid and is usually preferred in cervical TFE. It usually is given in doses of 4-18 mg.

Triamcinolone is available as three different salts. Triamcinolone acetonide (Kenalog) provides a long acting response like betamethasone and dexamethasone and is preferred in epidural injections. However, triamcinolone has 1/5 to 1/6 the steroid potency of betamethasone and dexamethasone.

Methylprednisolone has similar anti-inflammatory effects to triamcinolone. It has an intermediate duration of action. Typical doses range from 40 mg to 80 mg.

Indications for Epidural Steroid Injections

1)      Disc herniations or degenerations

2)      Spinal nerve root compression

3)      Spinal nerve root inflammation

4)      Spinal stenosis

     5)      Spondylolisthesis

Indications for Selective Nerve Root Blocks

1)      Evaluation of atypical extremity pain

2)      To resolve discrepancies when imaging studies and clinical presentation do not correlate

3)      Patients with multilevel imaging abnormalities, to more accurately define the levels for possible surgery

4)      Both for diagnostic and therapeutic purposes in postoperative patients with unexplainable or complex recurrent pain

5)      To assess anomalous innervations

     6)    To aid in the evaluation of patients with transitional vertebrae

Contraindications of Epidural Steroid Injections

1)      Patients unwilling to consent to the procedure

2)      True allergy to the local anesthetic, corticosteroid, or contrast agent

3)      Infection at the site of injection

4)      Systemic infection

5)      Coagulopathy which causes internal bleeding after the injection (INR>1.2 or Platelets <100000/mm³)

6)      Pregnancy

     7)      Unstable systemic diseases

Side Effects of the Medications

The side effects of steroids are insomnia, mood swings, euphoria, depression, post injection pain flare, facial redness, fluid retention, hypertension, hyperglycemia, headache, gastritis, necrosis of hip, suppression of adrenal glands, and menstrual irregularities. The most common side effects are insomnia and facial redness. Side effects are generally short lived.

The two most common systemic effects from epidural local anesthetics involve the central nervous system (CNS) and the cardiovascular system. Peak plasma concentration of epidural anesthetics occurs 10-20 minutes after injection, so it is recommended that patients be monitored for at least 30 minutes following an epidural injection.

Complications of Epidural Corticosteroid Injections

Relatively few serious complications occur in patients receiving epidural steroid
injection from well-trained and experienced physicians.  The most common complications are transient non positional headache for few days and increase in pain. 

        Potential complications of epidural steroid injections                 

     1.   Transient non positional headache
2.    Increase in pain
3.    Infection
4.    Dural puncture headache
5.    Nerve root injury
6.    Epidural hematoma in the spine
7.   Vasovagal attack and ataxia
8.    Pneumothorax during thoracic injections
9.    Paraplegia because of intraarterial injections during cervical injections which is preventable with a special imaging study known as digital subtraction angiography

More Information

Web Resources

Key References

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2. Fenton DS and Czervionke LF: Image-Guided Spine Intervention: Saunders: pp 73-126, 2003.

3. Koes BW, Scholten RJ, Mens JM, et al: Efficacy of Epidural Injections for Low Back Pain and Sciatica: A Systematic Review of Randomized Clinical Trials: Pain: 63: 279-88, 1995.

4. Rozenberg S, Dubourg G, Khalifa P, et al: Efficacy of Epidural Injections for Low Back Pain and Sciatica: A Critical Appraisal by a Franch Task Force of Randomized Trials: Rev Rhum: 66: 79-85, 1999.

5.Ackerman WE and Ahmad M: The Efficacy of Lumbar Epidural Steroid Injections in patients with Lumbar Disc Herniations: Anesth Analg: 104: 1217-22, 2007.

6. Schaufele MK, Hatch L and Jones W: Interlaminar versus Transforaminal Epidural Injections for the Treatment of Symptomatic Lumbar Intervertebral Disc Herniations: Pain Physician: 9: 361-366, 2006.

7. Derby R, Kine G, Saal JA, et al: Response to Steroid and Duration of Radicular pain as Predictors of Surgical Outcome: Spine: 17: S176-83, 1992.

8. Vad VB, Bhat AL, Lutz GE, et al: Transforaminal Epidural Steroid Injections in Lumbosacral Radiculopathy: A Prospective Randomized Study: Spine: 27:11-6, 2002.

9. Riew KD, Yin Y, Gilula L, et al: The effect of nerve-root injections on the need for operative treatment of lumbar radicular pain: a prospective, randomized, controlled, double-blind study: J Bone Joint Surg Am: 82-A: 1589-93, 2000.

10. Thomas E, Cyteval C, Abiad L, et al: Efficacy of transforaminal versus interspinous corticosteroid injection in discal radiculalgia: a prospective, randomized, double-blind study: Clin Rheumatol: 22: 299-304, 2003.

11. Scanlon GC, Moeller-Bertram T, Romanowsky SM, et al: Cervical transforaminal epidural steroid injections: more dangerous than we think?: Spine 15: 32(11): 1249-56, 2007.

12. Abbasi A, Malhotra G, Malanga G, et al: Complications of Interlaminar Cervical Epidural Steroid Injections: A Review of the Literature: Spine 32(19): 2144-51, 2007.