When a nerve is injected with local anesthetic, with or without a steroid such as methylprednisolone sodium succinate, pain may be temporarily relieved (nerve block
When a neurolytic substance is used the nerve is destroyed (neurolysis
) - the agent destroy neural structures involved in the perception of pain to promote long lasting analgesia.
In the 1920's, different agents for chemical neurolysis (phenol, ethyl alcohol, hypertonic saline, chlorocresol, etc.) were used to treat severe pain due to cancer and other inoperable chronic conditions and whose life expectancy is relatively short (less than one year).
All neurolytic substances are indiscriminate in action and injure large as well small fibers - neurolytic blocks therefore interfere with all aspects of nerve function both sensory and motor; the injury of cell membranes may produce dysaesthetic pain several months after a block.
With the advent of newer analgesics and the development of safer techniques for pain management, this method of pain relief has markedly diminished. Presently, these procedures are available as part of the management option for chronic pain and its use is usually based on the expertise of the pain specialist and the felt need of a selected group of patients.
Twycross R. Pain relief in advanced cancer. London, Churchill LivingstoneOxford University Press. 1994. Pages 512-517.