Standardization of anal sphincter electromyography: Utility of motor unit potential parameters

Advanced electromyography systems offer quantitative analysis of a number o f motor unit potential (MUP) parameters. However, only limited data are ava ilable on the diagnostic usefulness of these parameters. In the present stu dy, we compared the sensitivities of MUP parameters in revealing "neuropath ic" changes in the external anal sphincter (EAS) muscles in 56 patients exa mined 5-240 months after damage to the cauda equina or conus medullaris. Us ing multi-MUP analysis, 20 MUPs were obtained from patients' EAS muscles. T heir MUP parameters were compared with normative data from 64 controls. The diagnostic sensitivities of mean values/"outliers" of MUP parameters for d etecting neuropathic EAS muscles were calculated (area 25%/30%; number of t urns 18%/29%; size index 13%/ 24%; thickness 18%/18%; amplitude 17%/17%; sp ike duration 20%/9%; duration 15%/12%, number of phases 15%/11%; and their combination 51%/ 52%), Altogether, the cumulative sensitivity of multi-MUP analysis using both mean values and "outliers" was 62%. The combination of MUP parameters improves the diagnostic yield of MUP analysis, but the influ ence on specificity remains unknown. (C) 2001 John Wiley & Sons, Inc.