Conduction velocity in hexachlorophane neuropathy: correlation between electrophysiological and histological findings

After 2-3 weeks 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 oedema affecting some fibres and axonal degeneration of other fibres. After longer periods of exposure velocity and amplitude fell further. Velocity was reduced by 27% after 6-7 months treatment. In addition to intramyelin oedema and axonal degeneration, segmental demyelination was present in animals intoxicated for more than three months. There was no correlation between the degree of oedema and reduction of conduction velocity. It is concluded that intramyelin oedema 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.