Surface electrodes in perineal electromyography.

In 40 elderly male patients undergoing multiple urodynamic evaluations, surface electrodes were used for recording electromyographic (EMG) activity of pelvic sphincter muscles; placement site was the external anal sphincter. The measured wave form was displayed as an analog plot. Different types of surface electrodes were evaluated in selected patients. The EMG wave form measurements varied with the type of surface electrode used and placement of the electrode. Surface electrodes for external anal sphincter EMG resulting in optimum signal response require a small metallic recording surface with an adhesive that will secure the electrode to the skin, proper anatomic placement of the electrode, appropriate preparation of the skin surface at the site of application of the electrode, and capabilities for oscilloscope monitoring of the sphincter EMG signal wave form. If properly used, surface electrodes result in a signal amplitude and frequency that approach the quality of concentric needle electrodes.