Evoked potentials from the lower urinary tract. II. The spino-cortical neuraxis. A methodological study.

Spinal and cerebral evoked potentials (EPs) on stimulation of the dorsal nerve of the penis, clitoris, bladder wall and posterior urethra were recorded in 20 normal subjects (10 females and 10 males). Responses were obtained by computer averaging of multiple potentials registered over the spinal cord (L1) and cerebral cortex. Responses from the posterior tibial nerve were also recorded. Consistent cortical responses were obtained from the pudendal nerve, bladder wall and posterior urethra, whereas spinal responses were difficult to record. The maximum responses after stimulation of the pudendal nerve, bladder wall and posterior urethra were recorded over the midline of the scalp at CZ-2 cm point. The configuration of the somatosensory evoked potentials of the pudendal nerve had a W-shape with a consistent positive peak P1 (median 42.0 msec, range 39-45 msec), whereas the responses after endovesical and endourethral stimulation mainly were M-shaped with a prominent negative peak N1 (Bladder: mean 104.0 msec, range 75-112 msec and posterior urethra: median 103.0 msec, range 78-114 msec). Conduction times within the central spinal pathways could be calculated by subtracting the latencies of the peripheral spinal potentials from the central cortical potentials.