Interventional pain management

Interventional pain management or interventional pain medicine is a medical subspecialty which treats pain with invasive interventions such as facet joint injections, nerve blocks (interrupting the flow of pain signals along specific nervous system pathways), neuroaugmentation (including spinal cord stimulation and peripheral nerve stimulation), vertebroplasty, kyphoplasty, nucleoplasty, endoscopic discectomy and implantable drug delivery systems. Interventional pain management or interventional pain medicine is a medical subspecialty which treats pain with invasive interventions such as facet joint injections, nerve blocks (interrupting the flow of pain signals along specific nervous system pathways), neuroaugmentation (including spinal cord stimulation and peripheral nerve stimulation), vertebroplasty, kyphoplasty, nucleoplasty, endoscopic discectomy and implantable drug delivery systems. Early efforts at interventional pain management date back to the origins of regional analgesia and nerve blocks, and gradually evolved into a distinct specialty. Tuffer described the first therapeutic nerve block for pain management in 1899. Von Gaza developed diagnostic blockade in pain management, using procaine for determining the pain's pathways. Modern day contributors include Bonica, Winnie, Raj, Racz, Bogduk, and others. The term 'interventional pain management' was first used by pain management specialist Steven D. Waldman in 1996 to define the emerging specialty. The subspecialty of interventional pain management has received a specific specialty designation by the United States National Uniform Billing Committeeto allow its practitioners to bill Federal healthcare programs including Medicare and Medicaid. Physicians who practice interventional pain management are represented by a variety of pain management organizations including the Society For Pain Practice Management and the American Society of Interventional Pain Physicians. Radiotherapy is used when drug treatment is failing to control the pain of a growing tumor, such as in bone metastasis (most commonly), penetration of soft tissue, or compression of sensory nerves. Often, low doses are adequate to produce analgesia, thought to be due to reduction in pressure or, possibly, interference with the tumor's production of pain-promoting chemicals. Radiopharmaceuticals that target specific tumors have been used to treat the pain of metastatic illnesses. Relief may occur within a week of treatment and may last from two to four months. A neurolytic block is the deliberate injury of a nerve by the application of chemicals (in which case the procedure is called 'neurolysis') or physical agents such as freezing or heating ('neurotomy'). These interventions cause degeneration of the nerve's fibers and temporary interference with the transmission of pain signals. In these procedures, the thin protective layer around the nerve fiber, the basal lamina, is preserved so that, as a damaged fiber regrows, it travels within its basal lamina tube and connects with the correct loose end, and function may be restored. Surgically cutting a nerve severs these basal lamina tubes, and without them to channel the regrowing fibers to their lost connections, a painful neuroma or deafferentation pain may develop. This is why the neurolytic is preferred over the surgical block. Surgical cutting or destruction of peripheral or central nervous tissue is now rarely used in the treatment of pain. Procedures include neurectomy, cordotomy, dorsal root entry zone lesioning, and cingulotomy. Neurectomy involves cutting a nerve, and is (rarely) used in patients with short life expectancy who are unsuitable for drug therapy due to ineffectiveness or intolerance. The dorsal root or dorsal root ganglion (that carry mostly sensory signals) may be usefully targeted (called rhizotomy); with the dorsal root ganglion possibly the more effective target because some sensory fibers enter the spinal cord from the dorsal root ganglion via the ventral (motor) root, and these would not be interrupted by dorsal root neurectomy. Because nerves often carry both sensory and motor fibers, motor impairment is a possible side effect of neurectomy. A common result of this procedure is 'deafferentation pain' where, 6–9 months after surgery, pain returns at greater intensity. Cordotomy involves cutting into the spinothalamic tracts, which run up the front/side (anterolateral) quadrant of the spinal cord, carrying heat and pain signals to the brain. Pancoast tumor pain has been effectively treated with dorsal root entry zone (DREZ) lesioning – damaging a region of the spinal cord where peripheral pain signals cross to spinal cord fibers. This is major surgery, carrying the risk of significant neurological side effects. Cingulotomy involves cutting the fibers that carry signals directly from the cingulate gyrus to the entorhinal cortex in the brain. It reduces the unpleasantness of pain (without affecting its intensity), but may have cognitive side effects.