Electrical Interference in Clinical Practice: A Conceptual and Practical Approach.

Electrical Interference (EI: radiated electromagnetic and/or power line interference) is a common problem in clinical neurophysiology with many causes and thus various conceivable solutions. Although newer digitized electrodiagnostic (EDX) systems have markedly reduced EI issues, it remains a possible impediment in achieving high quality studies. So that the electrodiagnostic medicine consultant (EMC) can problem solve EI, this monograph details the fundamental functional concepts and terminology of electronic amplification and recording electrodes from a practical perspective.

Volume conduction: Extracellular waveform generation in theory and practice.

The extracellular waveform manifestations of the intracellular action potential are the quintessential diagnostic foundation of electrodiagnostic medicine, and clinical neurophysiology in general. Volume conduction is the extracellular current flow and associated voltage distributions in an ionic conducting media, such as occurs in the human body. Both surface and intramuscular electrodes, in association with contemporary digital electromyographic systems, permit very sensitive detection and visualization of this extracellular spontaneous, voluntary, and evoked nerve/muscle electrical activity.

Positive sharp wave origin: evidence supporting the electrode initiation hypothesis.

This investigation analyzes the temporal characteristics of maximal depolarization times for three waveforms: end-plate spikes, fibrillation potentials, and positive sharp waves (PSWs) to provide support for the electrode initiation hypothesis of PSW induction. The maximal depolarization times for PSWs are documented to comprise two distinct populations conforming to relatively short and comparatively longer maximal depolarization times. Those PSWs with short maximal depolarization times were found to be equivalent to end-plate spike maximal depolarization times, whereas those with longer times were comparable to fibrillation potentials.

Propagated insertional activity: a model of positive sharp wave generation.

In this study we utilized a dual monopolar needle recording technique to assess propagated electromyographic insertional activity from the same single muscle fiber in order to characterize different categories of insertional activity. A total of six combinations of insertional activity were identified. Only two fundamental types of single muscle-fiber insertional discharge configurations were generated: biphasic initially-negative and monophasic positive.