Evaluation of Nerve Block after Phenol and Ethanol Injection

ABSTRACT

OBJECTIVE:To evaluate the axonal degeneration after nerve block with phenol and ethanol injection into tibial nerve. METHOD: Tibial nerves of thirty Sprague-Dawley rats were exposed. For the developement of neuropathic pain, the method of intraneural injection was performed. Five percent phenol, 90% ethanol or normal saline were injected into the epineurial sheath of tibial nerve at each group. The mechanical and thermal allodynia were evaluated in post- injection 1, 2, 3, and 4 weeks. The mechanical allodynia was evaluated by withdrawal response to 10 stimulations with von Frey hair. Thermal allodynia was tested by withdrawal response to 5 stimulations with acetone. Motor nerve conduction study was performed in post-injection 1, 2, and 4 weeks. RESULTS: In behavioral test, the experimental group exhibited increased withdrawal response to mechanical and cold stim ulation, but there was no significant difference between two groups, phenol and ethanol groups. In motor nerve conduc tion study, compound motor action potential amplitude loss were observed in experimental group, but there was no significant difference between two groups, phenol and ethanol groups. CONCLUSION: These results suggest that axonal degeneration of ethanol is roughly similar to those of phenol block.