Cross Talk--The Paradoxical Transmission of a Nerve Impulse

Abstract

THIS COMMUNICATION concerns phenomena resulting from the activation of inactive nerve fibers by the action current traveling in active fibers. This electrical transmission of a nerve impulse at a false synapse (ephapse) is readily demonstrated in the laboratory. When responsible for clinical symptoms, such misdirection does not readily lend itself to proof. However, Sjoerdsma and Gaynor¹ described a striking example of nerve stimulation which they attributed to muscle action currents. Their patient exhibited vigorous abdominal pulsations suggesting the presence of a large abdominal aneurysm. Fluoroscopical study showed the pulsations were caused by contractions of the left leaf of the diaphragm occurring synchronously with each cardiac systole. The patient proved to have alkalosis with latent tetany, and the phenomenon ceased when electrolyte balance was restored. These authors uncovered reports of three similar cases. They pointed out the proximity of the left phrenic nerve to the pericardium and postulated that