In medical terms, an intervention is to take some action to modify an effect, usually an effect of a disease process (e.g., taking antibiotics to stop an infection). Over the past decade, there has been an increasing use of the phrase "interventional pain management." In the context of our definition, this implies a physician takes some action to modify or manage the effects of pain. Interest in interventional pain management has grown over the last five to 10 years as evidenced by the number of medical societies and organizations created dedicated to this type of pain management.

An intervention may be anything from words to medications to surgery, but the phrase "interventional pain medicine" has come to include the diagnosis and treatment of pain and related disorders by applying techniques that directly interact with the structures mediating the pain. This generally involves introducing medications, electrical current, heat, cold, or chemicals into the body at sites involved in the production of pain. These sites may range from the skin to the brain itself. Interventions may be performed diagnostically to help physicians determine which structures are generating or involved in producing the pain. Interventions may be therapeutic in that they treat a disease process causing pain or relieve symptoms for as long as possible.

Diagnostic Interventions
In pain medicine, diagnostic procedures are used to either identify the source of pain (e.g., which nerve, if any) or to determine the cause of pain (e.g., which disease, if any). Ideally, physicians try to identify the direct cause of pain such as the presence of a disease or injury. If a physician is able to identify a disease or injury, he or she may treat it directly. Identifying the source of pain may be necessary when a specific cause of the pain cannot be identified. Some diagnostic interventions are not designed to determine the source or cause of the pain, but to determine the mechanism of the pain. The mechanism of pain gets at the biological and chemical ways that pain is triggered in specific sites. This might have to do with sensitizing receptors to normal stimuli such as touch or pin prick, or creating irritability in nerves that causes them to send false messages to the brain signaling pain. Sometimes other parts of the nervous system such as the sympathetic or autonomic nervous system play a role in how the pain is generated. An example of such a diagnostic intervention is a sympathetic block in complex regional pain syndromes (formally called reflex sympathetic dystrophy, RSD, or causalgia). Most diagnostic interventions, however, are directed at identifying the source of the pain, that is, the structure from which the pain is coming.

Diagnostic interventions generally involve introducing a needle at the location of a nerve going to an area that hurts. Most commonly these techniques are performed under the guidance of x-ray pictures or some type of imaging to precisely locate the position of the needle or probe. Such procedures typically are performed under local anesthesia (meaning the patient is awake and aware, but does not feel pain in the area where the needle or probe is inserted). These types of interventions are called diagnostic blocks and attempt to briefly anesthetize the nerve thought to be involved in mediating the pain. These are most commonly used in the diagnosis of spine-related pain such as low back pain, thoracic, or neck pain. Often single nerves are blocked with a local anesthetic agent such as lidocaine (short acting) or bupivicaine (long acting), much as a dentist might numb the teeth for drilling. While the anesthetic is working, the patient should feel relief of the pain if that particular nerve is the one involved in sending pain messages to the brain. The structure to which the nerve goes (e.g., leg or arm) will be numb on occasion but often physicians can use a dose of anesthetic that preserves the patient's ability to feel touch and pressure but eliminates the pain. The primary goal of diagnostic interventions is to decide if the particular area blocked is involved in the pain generation.

One specific diagnostic intervention involves producing the pain regularly experienced. This procedure is known as discography. The physician inserts a needle into the disc and injects contrast fluid, which is visible on x-ray, under pressure into a lumbar or cervical disc. If the disc is painful, the regular pain experienced from that disc will be provoked. If the disc is not painful, then only pressure sensations will be felt. Hence, not all diagnostic interventions are designed to relieve pain, but rather to identify exactly where the pain occurs.

Therapeutic Interventions
Interventional pain management takes many of the diagnostic interventions and attempts to produce long-term relief of the pain by increasing the amount or type of material injected. Technically, the approaches using needle procedures are similar to diagnostic blocks. Such interventions include epidural steroid injections (ESI), facet joint injections, single nerve root blocks, peripheral nerve injections, sacroiliac joint injections, and many others. Therapeutic interventions may apply chemicals, heat, and cold or use surgical procedures that destroy nerves (neuroablation) to achieve relief of the pain mediated through specific nerves as shown by previously performed diagnostic blocks. The use of radiofrequency heating and cryogenic cooling is common. Radiofrequency waves generated into tissue by a probe cause the tissue to heat. The heating can be sufficient to cause temporary shut down of nerve fibers or even permanently shut down the nerves. Cryogenic cooling achieves the same result by freezing the tissue or lowering its temperature to temporarily shut down the nerves. The most frequently used substance injected for temporary relief of pain due to swelling and inflammation is a powerful anti-inflammatory steroid hormone called cortisone.

An increasing area of therapeutic interventional pain medicine is known as neuromodulation. This involves applying electricity or administering medications directly to the nervous system to relieve pain. Electrical stimulation of the nervous system has become an effective tool for relieving pain due to nerve injury. Electrical stimulation requires placing a probe called an electrode into a target in the nervous system (e.g., the peripheral nerve, spinal cord or brain) that is involved in the pain. An electrical stimulus is applied to relieve the symptoms. Another powerful tool for pain management is the direct delivery of medication into the spinal fluid for the treatment of many types of pain. Using this type of neuromodulation, the physician places a tiny tube called a catheter into the spinal fluid and connects it to a pump implanted under the skin to administer medication continuously.