• EMG usually undertaken in combination with other urody-namic techniques
• Can be performed with the patient supine, sitting, or standing
• Electrical activity can be picked up either by needle or surface electrodes
• In the female, the needle electrodes are placed directly in the EUS, located about 1 inch in from the external meatus. Needles placed at the 1 o'clock and 11 o'clock position provide the most reliable information
• In males, the EUS is reached by inserting the electrodes between the base of the scrotum and the rectum, parallel to the rectum, about 2 inches deep to skin
• If placement is correct, the EMG should demonstrate increased muscle activity with voluntary tightening of the EUS and decreased muscle activity upon relaxation
• Surface electrodes, including skin patch and anal plug electrodes, are applied to the skin surface close to the sphincter and therefore detect electrical activity from groups of adjacent motor units. Patches are placed on either side of the external anal sphincter, as close to the rectal mucosa as possible, at the 3 and 9 o'clock position. Surface electrodes are less uncomfortable but have decreased reliability and reproducibility compared to their needle counterparts
• Electrical activity is either displayed graphically on a monitor screen or audibly on special speakers and studies interpreted in real time, as they are being performed
Standard kinesiological EMG does not diagnose neuropathy but simply demonstrates the effects of neuropathy on the EUS. However, motor unit EMG is another type of sophisticated neu-rophysiological investigation which can accurately detect dener-vation or myopathy in the striated pelvic floor musculature. This is more invasive and requires an experienced neurologist with considerable experience in such techniques.
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