Effects of phenol solutions on the nerve roots of the cat: An electrophysiological and histological study

Abstract

In order to elucidate certain problems arising from the use of solutions of phenol in iophendylate (Myodil, Pantopaque) injected intrathecally or epidurally in patients with chronic severe pain, these solutions were applied to the nerve roots of the cat. The effect on the roots were investigated electrophysiologically and histologically. It had previously been reported that such solutions block conduction in nerve fibres differentially in the same manner as all local anaesthetics. It is now shown that in addition to this local anaesthetic action, the solutions destroy nerve fibres and that this destruction is non-differential, all sizes and types of nerve fibres being equally affected. The amount of destruction of nerve fibres is related to the concentration and to the amount of phenol applied, and to the duration of its application. Even the weakest solution of which the effects were examined histologically (1%) was found to cause considerable destruction of nerve fibres of all calibres, both myelinated and non-myelinated. The solutions destroy nerve fibres scattered in bundles throughout the nerve roots and only rarely destroy all nerve fibres of one root. In the light of these facts, the course of events when the solutions are injected intrathecally in patients with chronic severe pain is discussed.