What are phenol blocks?

Nerve blocks. Phenol compounds are used to block nerves that may be diseased in such a way as to cause chronic, non-remitting painful conditions. Unlike a local anesthetic, which may allow temporary relief, phenol compounds act be destroying the nerve itself. They are typically used as a final resort.
Neurolytic. Which means it destroys a nerve. The reason to use it would be in extreme situation where all other pain interventions fail or the problem is severe and recurrent.
Nerve blocks. If a nerve is blocked well with a local like Lidocaine phenol can provide longer relief.