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. This information is then utilized in a proposed standard operating protocol (SOP) to help the EMC address a wide variety of EI sources. Three major EI sources are considered: the EDX system/operator error, the environment, and the patient. The first is a thorough assessment of the recording electrodes from the perspective of clean electrodes, security of attachment, appropriate gel application, proper lead connections to both the patient and instrument, and similarity of electrode composition. Second is how adverse environmental conditions are mitigated through isolating the EDX instrument from nearby large generator sources, unplugging unnecessary equipment, keeping the amplifier close to the patient along with short and braided electrode leads, and utilize filtering (both 60 Hz and total bandwidth) with appropriate caution to avoid unwanted signal distortion. Third, the patient and EMC interaction must be considered. Specifically, all electronic devices that can be removed should be powered down and relocated as far as feasible from the EDX system, including digital watches, cell phones, TENS units, and other such devices. A systematic application of the above proposed protocol should solve the majority of EI issues.