The selective nerve root block procedure is an injection of a small amount of steroid and numbing medication around a very specific nerve root/spinal nerve that exits out of the spinal cord. The selective nerve root block procedure can be done in the cervical (neck), thoracic (chest) and lumbar (low back) areas. This injection allows the doctor to determine exactly what nerve root or roots are being affected. This can be a diagnostic test (finding out which nerve is involved) or therapeutic test (providing pain relief) depending on the medications that are injected. Although uncommon, risks from the selective nerve root block procedure may include bleeding, infection, allergic reaction to the medications, puncture of the membrane that covers the spinal cord (dura), nerve damage and paralysis.