Nerve roots exit the spinal cord and then come together to form nerves that travel into the arms or legs. These nerves allow movement and sensation of the arms, chest wall and legs. This test provides important information about which nerve is causing pain by temporarily numbing a specific nerve root. If the patient’s pain is reduced after the injection, that nerve may be causing the pain. By confirming or eliminating the source of pain, the test allows the physician to develop appropriate treatment, which could include further nerve blocks and/or surgery. This test takes approximately 15-30 minutes to complete for one nerve, plus 90 minutes of observation; testing additional nerves requires extra time.