EVALUATION OF THE MOTOR AND SENSORY COMPONENTS OF THE PUDENDAL NERVE

Extensive neurophysiological investigations consisting of different te chniques to evaluate the efferents and afferents of the pudendal nerve were carried out in 27 healthy subjects. These investigations include d motor evoked potential recordings from the external anal sphincter i n response to magnetic stimulation of the cortex and lumbosacral roots , measurement of sacral reflex latency to magnetic and electrical stim ulation, and cortical sensory evoked potential recording after stimula tion of the dorso-genital nerve and anal canal. Motor latencies after transcranial magnetic stimulation to the anal spincter were 25.1 +/- 2 .9 msec at rest and 20.9 +/- 2.0 msec with voluntary sphincter contrac tion (facilitation). Motor latency after lumbosacral root stimulation was 3.7 +/- 1.0 msec. Mean sacral reflex latency after magnetic stimul ation was 43.8 +/- 11.2 msec and was significantly longer than after e lectrical stimulation (37.0 +/- 7.2 msec; P < 0.05). P1 latency of the sensory evoked potentials after dorso-genital nerve stimulation was 4 0 +/- 3 msec and was significantly shorter than after anal stimulation 46 +/- 3 msec (P < 0.01). Evoked potential recording allows us to stu dy both upper and lower motor neuron components to the anal sphincter. The present study paves the way for the combined application of these tests in the evaluation of disorders of the pelvic floor.