Motor evoked potentials from the striated urethral sphincter: a comparison of concentric needle and surface electrodes

AIMS: The aim of this study is to compare two different surface electrodes (intravaginal and intraurethral) with the concentric needle as a criterion standard and concomitant testing of the levator ani as a potential contaminator.

METHODS: Thirty healthy women with a mean age of 52 years. Bland-Altman plots were used to compare recorded latencies from the various electrodes and muscles.

RESULTS: There was no significant difference between the latencies recorded with the various electrodes from either muscle, but the limits of agreement were wide. However, the concentric needle electrodes proved more reliable with a higher rate of reproducible responses.

CONCLUSIONS: We did not encounter major difficulties in using the concentric needle electrode for recordings in the external urethral sphincter, and this electrode was also more reliable than either surface electrode. Therefore, we advocate the use of concentric needle electrodes in future studies.