Certain pain syndromes are difficult to diagnose, and novocaine injections to deaden specific anatomic structures may be helpful in localizing the source of the pain. These injections are also known as .blocks, as the numbing medicine instilled attempts to block the pain signals and temporarily stop the pain. Diagnostic injections commonly performed include facet blocks and selective nerve root blocks.
Facet joint injection with an anesthetic can be done to see if an arthritic facet joint is a source of pain. A steroid compound is often added to possibly provide some longer-term therapeutic benefit. Pain emanating from the facet joints is also known clinically as facet syndrome." In facet syndrome, pain is typically brought on suddenly by certain body positions and relieved by others. A facet block is an injection into the facet joint itself under radiographic guidance (intraarticular injection) for the purpose of immediate short-term and longer pain relief. An initial injection of a small amount of contrast dye may be done to ensure the joint has been entered after which a local anesthetic (such as novocaine) and sometimes a steroid are injected. If successful pain relief is achieved, even for a short period of time, a rhizotomy, or transection of the adjacent sensory nerve to the facet joint, may be considered for longer term pain relief. Symptoms may return from within several months to several years. Spinal fusion may also be an option for intractable pain due to facet joint disease.
Selective nerve root blocks can also be used to both find the cause of pain (diagnostic) and to treat pain (therapeutic). If the physician suggests a nerve root block, it is to identify the spinal nerve or nerves responsible for any radiating arm or leg symptoms. An anesthetic, or local pain killer, is injected under radiographic guidance (either fluoroscopy or CT guidance) around the nerve that supplies the painful area. If the choice of nerve is correct, pain impulses are blocked, the patient experiences relief, and the source of the pain is identified. Nerve blocks are sometimes used as regional anesthesia in surgical procedures. A nerve block procedure is an outpatient procedure and usually takes about 30 min. Patients typically go home immediately after the procedure. In some instances, corticosteroids are also injected in an attempt to provide long-term relief. Multiple visits may be required to test more than one spinal nerve.