Which neurolytic agents are used in IV neural blocks for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Answer

Examples of neurolytic agents include alcohol in concentrations of 35-100%. Alcohol produces nerve fiber destruction, which results in wallerian axonal degeneration. If cell bodies at the level of the dorsal root ganglia are destroyed, no regeneration takes place, whereas if they are destroyed only partially, regeneration may occur.

Phenol often is used to induce prolonged sympathetic, somatic nerve, subarachnoid, and epidural blockade. Phenol is similar to alcohol in regards to its potency and nonselective damage to the nervous system. Injection concentrations of phenol usually vary between 5% and 8%. Concentrations above 5%, when applied to peripheral nerve, cause protein coagulation and necrosis with axonal degeneration and subsequent wallerian degeneration.

Injection of glycerol into the trigeminal ganglion has been popularized for the treatment of neuralgia because of its capacity to relieve pain without causing significant sensory deficits. Topical application of a 50% glycerol solution to nerves causes localized subperineurial damage, whereas intraneural injection is more damaging and causes axinolysis.

Cryotherapy, laser, and radiofrequency lesions are currently under investigation and are advocated as being effective for neurolytic procedures when performed by trained and experienced interventionists. Further clinical research is needed to develop methods that preferentially block nociceptive pathways (ie, strict neurolytic blockade that spares large myelinated sensory fibers).


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