Neurolytic block
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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").[1] These interventions cause degeneration of the nerve's fibers and the fibers' myelin sheaths, and temporary interference with the transmission of pain signals. A neurolytic block does not damage the protective casing around the myelin sheath, the basal lamina, so that as a damaged fiber and its myelin sheath regrow, they travel within their basal lamina and connect with the correct loose end, and function may be restored. Surgical cutting of a nerve severs the basal laminae, and without these tubes to channel the regrowing fibers to their lost connections, a painful neuromata or deafferentation pain pain may develop. This is why the neurolytic is preferred over the surgical block.[2]
A brief "rehearsal" block using local anesthesia should be tried before the actual neurolytic block, to determine efficacy and detect side effects.[3] The aim of this treatment is pain elimination, or the reduction of pain to the point where opioids may be effective.[3] Though the neurolytic block lacks long-term outcome studies and evidence-based guidelines for its use, for patients with progressive cancer and otherwise incurable pain, it can play an essential role.[2]
Targets for neurolytic block include the celiac plexus, most commonly for cancer of the gastrointestinal tract up to the transverse colon, and pancreatic cancer, but also for stomach cancer, gall bladder cancer, adrenal mass, common bile duct cancer, chronic pancreatitis and active intermittent porphyria; the splanchnic nerve, for retroperitoneal pain, and similar conditions to those addressed by the celiac plexus block but, because of its higher rate of complications, used only if the celiac plexus block is not producing adequate relief; hypogastric plexus, "for cancer affecting the descending colon, sigmoid colon and rectum," as well as cancers of the bladder, prostatic urethra, prostate, seminal vesicles, testicles, uterus, ovary and vaginal fundus; ganglion impar, for the perinium, vulva, anus, distal rectum, distal urethra, and distal third of the vagina; the stellate ganglion, usually for head and neck cancer, or sympathetically mediated arm and hand pain; the intercostal nerves, which serve the skin of the chest and abdomen; and a dorsal root ganglion may be injured by targeting the root inside the subarachnoid cavity (fig.5), most effective for pain in the chest or abdominal wall, but also used for other areas including arm/hand or leg/foot pain.[3]
References
- ^ Scott Fishman; Jane Ballantyne; James P. Rathmell (January 2010). Bonica's Management of Pain. Lippincott Williams & Wilkins. p. 1458. ISBN 978-0-7817-6827-6. Retrieved 15 August 2013.
- ^ a b Williams JE. Nerve blocks: Chemical and physical neurolytic agents. In: Sykes N, Bennett MI & Yuan C-S. Clinical pain management: Cancer pain. 2nd ed. London: Hodder Arnold; 2008. ISBN 978-0-340-94007-5. p. 225–35.
- ^ a b c Atallah JN. Management of cancer pain. In: Vadivelu N, Urman RD, Hines RL. Essentials of pain management. New York: Springer; 2011. doi:10.1007/978-0-387-87579-8. ISBN 978-0-387-87578-1. p. 597–628.
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