The origin of spontaneous discharges in acquired neuromyotonia.: A Macro EMG study

Objective: To study the generator sites of spontaneous discharges in patients with immune-mediated neuromyotonia. Methods: Macro EMGs triggered by both spontaneously and voluntarily activated single action potentials were recorded and the mean peak-to-peak amplitude and area of the macro motor unit potentials were compared in two patients with typical acquired neuromyotonia,having positive antibodies against voltage-gated potassium channels. Results: Mean peak-to-peak amplitude and area of Macro EMG motor unit potentials (macro MUPs) triggered by spontaneous discharges were significantly smaller than those triggered by voluntary activation in both patients. However, a few macro MUPs triggered by spontaneous discharges resembled those triggered by voluntary activation. Conclusions: Spontaneous discharges in two patients with immune-mediated neuromyotonia seem to be mostly generated at sites distal to the terminal axon branching points. Significance: This finding may provide a new insight in the understanding of spontaneous discharges in immune-mediated neuromyotonia. (c) 2005 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.