Latency of compound muscle action potentials of the anal sphincter after magnetic sacral stimulation

The aim of this study was to present the failure rate and normal values for motor latency of the anal sphincter after magnetic sacral stimulation (LMS S) using a modified recording technique. A bipolar sponge electrode was pla ced in the anal canal for recording. A ground electrode was placed in the r ectum to reduce stimulus artifact. Magnetic stimulation was induced through a twin coil energized by a Maglite-r25 generator. Two groups were examined : 14 healthy volunteers and 14 patients with a spinal cord injury (SCI) abo ve the conus. Nine of 56 studies (16%) failed. There were no significant di fferences in latency between right- and left-sided stimulation or between t he healthy group and the SCI patients. As described, LMSS measurements are minimally invasive and have a low failure rate. They may be used to test th e integrity of the distal motor pathway in patients with bladder or bowel d ysfunction who may benefit from continuous electrical sacral root stimulati on. (C) 2001 John Wiley & Sons, Inc.