Cerebral evoked potentials after stimulation of the posterior urethra in man

Cerebral evoked potentials (EPs) were recorded in 25 neurologically normal subjects aged 22-73 years (mean 44.0) after stimulation of the posterior urethra (PU) and the pudendal nerve. After maximal PU stimulation 2 different configurations of the potential were found. In 12 cases a simple bi-triphasic wave form was recorded while in 12 cases there was a bifid form of the first negative wave. In 1 case identical EPs were recorded after PU and pudendal nerve stimulation. It was concluded that (1) PU stimulation excites fibres in the pudendal nerve at higher stimulation strength, resulting in a bifid wave form of the cerebral evoked potential in some individuals, (2) the most prominent negative peak, N1, with a latency of 102.1 +/- 13.2 msec, is the most reproducible part of the PU-evoked potential, (3) the N1 is probably transmitted through A delta fibres localized in the pelvic nerves, (4) there are differences between individuals concerning pudendal and pelvic nerve involvement in afferent innervation of the urethra.