Epidural Nerve Block

Radicular pain from lumbar spine (low back), thoracic spine (mid back) and cervical spine (neck) disorders can be treated by non-surgical means.  One technique is through epidural nerve blocks.  Epidural nerve blocks, also known as epidural steroid injections (ESIs), are corticosteroid injections used to decrease pain and inflammation.

Sharp radiating pain which shoots from the low back into the hips, buttocks or lower limb(s) in a specific pattern is defined as radicular pain.  Sharp shooting pain which shoots from the neck into the shoulder, shoulder blade and upper limb(s) in a specific pattern is also defined as radicular pain. Finally, sharp shooting pain which shoots from the mid back into the upper limb (s), flank, chest or abdomen in a specific pattern is also defined as radicular pain.

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Radicular distribution is defined as specific areas of the body supplied by specific nerves from the lumbar, thoracic or cervical spine.  Inflammation of the nerve root results in radicular pain.  A lesion in the nerve root can also result in radicular pain as can an injury to the nerve root. When a lesion, injury or inflammation is present in a nerve root, the following can occur:

  • weakness of the muscles supplied by the involved nerve root,
  • decreased reflexes,
  • radicular pain,
  • numbness, and
  • tingling.

For drugs administered orally (by mouth), absorption may begin in the mouth and stomach. However, most drugs are usually absorbed from the small intestine. Most of the steroid, taken orally, passes through the intestinal wall and travels to the liver before being transported via the bloodstream to its target site (affected nerve root). The intestinal wall and liver chemically alter (metabolize) many drugs, decreasing the drug reaching the bloodstream and eventually the affected nerve roots. ESIs are advantageous, compared to oral steroids, because the medication is delivered specifically to the affected nerve roots.  Because of this, the overall dose of epidural steroids required is much lower than oral steroids resulting in fewer side effects involving other systems of the body.

ESIs are more effective for nerve root inflammation compared to nerve root lesions. ESIs are more effective for mild nerve root injuries compared to moderate and severe nerve root injuries.

ESIs can be both diagnostic and therapeutic.  Prolonged pain relief increases the likelihood that inflammation in or near the epidural space was the source of the pain.  By decreasing inflammation, ESIs are therapeutic because untreated chronic inflammation can lead to swelling, degeneration, and scarring of nerve roots and tissues.

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ESIs are most effective if they are combined with other treatment modalities such as physical therapy, improved posture, weight loss, manual therapy, chiropractic therapy, short-term bed rest, and/or low dose medications.  Resolving personal problems (financial, marital and work-related) and treating psychological problems are also effective in decreasing radicular pain.

The major cause of radicular pain originating from the cervical spine, thoracic spine and lumbar spine is inflammation of the nerve root in the epidural space.  Causes include

  • leakage of inflammatory chemicals from the disc,
  • nerve root blood supply being compressed, and
  • inflammation or compression of the dorsal root ganglia (cell bodies of nerves that send painful sensations to the spinal cord and brain).

Steroids decrease inflammation in the epidural space and/or nerve root by these mechanisms:

  • Inflammatory chemicals are inhibited.
  • Transmission of pain signals from pain nerve fibers is inhibited.
  • Blood vessel leakage is decreased.

ESIs can treat lumbar, thoracic and cervical radicular pain in these conditions:

  • foraminal stenosis;
  • spinal disc herniation, protrusion, bulge or extrusion;
  • post-surgical pain;
  • degenerative disc disease; and
  • postherpetic neuralgia.

ESIs should not be performed if you have these conditions:

  • allergic reactions to anesthetic, corticosteroid or contrast containing iodine;
  • history of bleeding disorder or on blood thinners;
  • infection; and
  • spinal cord compression.

If allergic to corticosteroids or contrast, alternative medications can be used by your doctor when performing the ESI.

In pregnant women, ESIs should not be performed with fluoroscopy (x-ray guidance).

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Blood glucose levels should be well controlled in diabetic patients because ESI steroids may temporarily increase blood glucose levels.  Diabetic patients receiving ESIs should not stop their diabetic medications and should continue to adhere to a strict diabetic diet.

Because fluid retention (retaining water) may occur with steroids, patients with congestive heart failure should be carefully monitored.

Studies have shown that ESIs performed without fluoroscopy (x-ray guidance) result in incorrect placement of the medication in 30% of cases.

Benefits of ESIs include

  • decreased radicular pain,
  • decreased spinal pain,
  • reduced pain medication use,
  • allowance for participation in physical therapy by decreasing pain,
  • improved performance of activities of daily living, and
  • improved sleep patterns.

The longer the period in which symptoms have occurred, the less effective are ESIs.  ESIs are also less effective in these situations:

  • previous back surgery;
  • work-related injuries;
  • injuries involving litigation;
  • currently smoking; and
  • repetitive heavy lifting, bending or stooping at home or work.

Risks of ESIs include

  • infection,
  • bleeding,
  • nerve root injury,
  • spinal headache,
  • spinal cord injury, and
  • allergic reaction.

Correct technique, extensive clinical experience, and proper equipment result in a complication rate which is minimal when ESIs are performed.

The medical literature is not clear as to the exact number of ESIs which should be administered to treat spinal and radicular pain.  In general, each injection should be performed at least two weeks apart and, if there is no benefit after the second injection, a third one should not be performed.  The patient’s status should be assessed before each ESI.

Cervical and thoracic epidural steroid injections can be performed using interlaminar and transforaminal approaches.  Transforaminal, interlaminar and caudal approaches can be used in lumbar epidural injections.

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The interlaminar approach is performed at the midline or just lateral to the midline.  The transforaminal approach is performed by placing the needle into the neural foramen, the exit hole for the nerve root.  Caudal epidural injections are performed by placing a needle into the epidural space at the sacral canal (just above the tailbone).

Medications used in ESIs include a steroid, anesthetic, and contrast agent. As discussed, the corticosteroid preparation decreases inflammation.  The anesthetic is used to numb “the skin” and underlying tissue to allow the procedure to be performed comfortably.  In general, the corticosteroid preparation results in decreased pain in one to five days. The radiographic contrast agent is used in ESIs to confirm accurate placement of the needle in the proper location.

ESIs, combined with other treatment modalities, can decrease spinal and radicular pain. They can also improve functionality and enhance the quality of life.

Jose Veliz MD is the medical director of Palomar Spine & Pain, in Escondido, CA (North San Diego County).

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