More About Interventional Pain Management...

    Introduction

Pain management continues with increasing popularity as patients and physicians become more familiar with the procedures and treatments rendered under the guise of the specialty. A textbook definition of interventional pain management will usually include all disciplines, however in common usage, interventional pain management most often refers to the procedure-oriented discipline, which is the focus of this article.   In situations where double-blinded, placebo-controlled studies are not possible, the evidence remains as the only measure of therapeutic utility for a given treatment. It is compilations of well-conducted studies that form the basis for an evidence-based approach to medicine. The factoids referenced in this discussion derive from the evidence-based literature.   Interventional pain management procedures involve the use of percutaneous needle type devices designed to treat pain at the source. The general mechanisms of relief occur through a variety of means: - high concentrations of cortisone type medications administered near the source frequently allows for decreased swelling and increased blood flow providing a better environment for the body to heal itself; - selective destruction of the nerve supply to a painful area can decrease pain while not impairing function; - removal or disruption of scar tissue often relieves pain; - decreasing pressure from within a disc can allow a protruded segment of the disc to return to its natural location thereby relieving pain in a variety of situations.   It is most frequently in the context of persistent back or neck pain, refractory to the other pain treatments (e.g., pharmacologic, chiropractic, physical medicine and rehabilitative), that a patient is finally referred to pain management. It is implicit in most referrals for pain management that a workup to rule out infections, cancer or other life threatening illnesses is already complete. A high percentage, if not the majority, of pain management interventions begin with the use of cortisone type medications administered empirically through any variety of means. The situation becomes difficult when the response to these treatments is not successful. Beyond the initial empirical interventions, effective uses of interventional procedures require a diagnosis. This article will reference the most popular of all interventional procedures to illustrate a couple of important concepts.

    Epidural steroid injections

Epidural steroid injections (ESIs) involve the introduction of relatively high concentrations of cortisone type medications into the spinal space “closer” to the source of the pain. It is fortunate in many situations that cortisone type medications, injected locally (or taken orally), prove interventional as they interrupt the inflammatory, painful process improving the environment for a natural healing process to take place; in this situation the source of the pain may never be known.   The apparent success of ESIs in the treatment of many types of pain has made “epidural” a household name. ESIs provide excellent short-term relief in the vast majority of patients however the pain often returns over time in a large percentage of patients. It is the amount of time that it takes for the pain to return to baseline that usually defines “success or failure” a definition that varies significantly by healthcare provider. In this context, ESIs can actually complicate the isolation of the pain culprit: there is usually excellent short-term relief followed by variable intermediate to long-term pain relief that is often just barely beneficial enough that more direct interventional procedures are not explored. Patients in chronic pain are usually grateful for any pain relief so the concept of “holding out for better” is sometimes a difficult decision for a patient to make.        It is in this type of situation that the precise origin of pain becomes important. There are multiple sources for back pain including facet joints, nerve roots, discs and sacroiliac joints each requiring a unique interventional pain procedure. Facet joints have been implicated as the source of pain in as much as 45% for low back, 48% for thoracic and 67% for neck pain. Disc related pain has been implicated in 26 - 39% for low back and 61% for neck pain. Sacroiliac joint pain has been implicated in 10 - 30% of patients with low back pain. ESIs are generally not effective treatment in a large percentage of the described sources of pain.

    How well does diagnostic imaging or physical examination delineate a pain
    source?

Patients often arrive to the pain management clinic under the impression that the cause of their pain is known. Many are able to recite x-ray findings, physical findings and their diagnosis. It seems logical that if there is an x-ray abnormality and pain, that the pain must be related to the x-ray abnormality: This is where the opportunity for intervention is often lost:  A recent study has shown that only approximately 1 in 7 patients without distinctive diagnostic imaging abnormalities and neurologic deficit (not pain) was diagnosed appropriately as to the cause of the pain and in a second study, 40-67% of patients referred to pain management centers had inaccurate diagnoses.

    So how does one make the diagnosis?

A diagnostic injection entails the administration of small amounts of local anesthesia precisely at the site of the suspected pain generator; if the pain resolves then the source of the pain has been confirmed allowing for specific treatments directed at the source; if the pain does not resolve then the source of the pain remains unknown requiring more diagnostic injections to isolate the source. The concept of diagnostic injections is straight forward however the fact that we are human complicates everything: It is estimated that approximately 30% or more of patients will report pain relief following a diagnostic injection for reasons other than the effect of the local anesthesia (placebo response); to improve the reliability of diagnostic injections, evidence shows that a second diagnostic injection will greatly reduce the placebo response however two diagnostic injections prior to the actual interventional procedure is not well received by patients or insurance companies.

    So what does this mean to a patient?

In a discipline as inexact as pain medicine, clear-cut answers are hard to find. When patients find themselves in the situation where they are receiving repetitive treatments of questionable benefit, it is of paramount importance that all avenues have been explored. Understanding that such a large percentage of pain may come from the facets, discs and/or sacro-iliac joints and that diagnostic imaging and physical findings are not diagnostic in a large percentage of circumstances simply means that the facets, discs and/or sacro-iliac joints must be carefully evaluated. These areas may yield specific, interventional opportunity for the relief of pain that is far superior to nonspecific treatment. The risks of trying to locate the source of the pain verses the risks of living with the pain are small. Patients owe it to themselves to take charge and make sure that opportunity for pain relief is not overlooked.