CONDUCTION-VELOCITY IN HEXACHLOROPHANE NEUROPATHY - CORRELATION BETWEEN ELECTRO-PHYSIOLOGICAL AND HISTOLOGICAL-FINDINGS

After 2-3 wk exposure to hexachlorophane, maximum motor nerve conduction velocity in sciatic nerves of rats was reduced by 7.5% and evoked muscle action potential amplitude by 9%. Histological examination at this stage showed intramyelin edema affecting some fibers and axonal degeneration of other fibers. After longer periods of exposure, velocity and amplitude fell further. Velocity was reduced by 27% after 6-7 mo. treatment. In addition to intramyelin edema and axonal degeneration segmental demyelination was present in animals intoxicated for > 3 mo. There was no correlation between the degree of edema and reduction of conduction velocity. Intramyelin edema has little or no effect on conduction velocity. Nodes of Ranvier are normal in the early stages of the lesion and this may contribute to the preservation of normal conduction. The electrophysiological findings can be attributed to secondary changes of axonal degeneration and segmental demyelination.