Prediction of Propagation Block on the Basis of Impulse Shape in Single Unit Recordings from Human Nerves

Abstract

The occurrence of impulse block was studied in single unit recordings and related to impulse shape when peripheral nerves were impaled with tungsten needle electrodes. Exposed nerves were exploited in frog and cat, and non-exposed nerves were exploited in man. Three different impulse shapes were seen: negative spikes of very short durations which nearly all propagated; positive double peaked spikes which all propagated; and positive single peaked spikes, some of which propagated and some which did not. Unitary impulses recorded with a needle electrode impaling the myelin apparently were positive and single peaked when the injury was minimal. Gradually a propogation delay might develop at the site of impalement giving rise to a double peak. Later the propagation may be blocked which is seen as a drop out of the 2nd peak. It was possible to predict in practically all cases whether the propagation was blocked or not from the shapes of the single unit impulses and their alterations as seen by the tungsten needle electrode.