Motor potentials of bulbocavernosus muscle after transcranial and lumbar magnetic stimulation: comparative study with bulbocavernosus reflex and pudendal evoked potentials.

Motor potentials of the bulbocavernosus muscle were recorded in 17 healthy subjects after transcranial and lumbar magnetic stimulation. The latencies (SD) were respectively: 22.9 (1.8) and 5.9 (0.4) ms. The central conduction time was 17.0 (2.5) ms. The bulbocavernosus reflex presented an onset at 34.5 (3.3) ms and a negative peak at 43.1 (3.9) ms. The cortical pudendal evoked potential was W shaped: the first peak had a latency of 35.4 (2.8) ms. The concurrent recording of motor potentials, bulbocavernosus reflex, pudendal evoked potentials gives a measure of peripheral and central, afferent and efferent neurological pathways related to pudendal nerve function.