Nerve Root Block / Transforaminal Injection

A nerve block injection is used to both diagnose and treat an inflamed spinal nerve. In this procedure, steroid is administered near the spinal nerve as it exits the intervertebral foramen (bony opening between adjacent vertebrae). The medication reduces inflammation and numbs the pain transmitted by the nerve.

How Does It Work?

Steroids in nerve blocks work by a combination of the following mechanisms:

  • It inhibits the action of certain enzymes such as phospholipase A that causes neural irritation and pain.
  • It block specific fibers (C fibers) within the nerve that results in lesser pain transmitted to the brain, and
  • It decreases the permeability of nerve fibers to receive blood, decreasing pain transmission. Through these mechanisms, the pain signals transmitted by the target nerve may be reduced.


Prior to the injection, the patient is sterilely prepped and draped. The skin over the treatment site is cleansed and numbed by injecting a local anesthetic. Injections are guided under fluoroscopy (continuous x-ray imaging) and contrast is administered to confirm placement. Lastly, steroid is injected near the spinal nerve root to deliver pain-relieving medication directly to the site of inflammation

Important Note

The injection may recreate the usual pain that has been experienced by the patient. Some patients, however, may experience no pain relief or short-term relief for a few weeks. The therapeutic effect can sometimes be delayed by a few days or weeks as the steroid becomes more effective. The pain-relieving effects of selective nerve root block injections are usually higher in patients who participate in strengthening exercises and physical therapy.

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