Papers Published

1. P. B. Yoo and W. M. Grill, Minimally-invasive electrical stimulation of the pudendal nerve: A pre-clinical study for neural control of the lower urinary tract, Neurourology And Urodynamics, vol. 26 no. 4 (2007), pp. 562 -- 569 .
   (last updated on 2009/09/02)

   Abstract:
   Aims: Electrical stimulation of afferent pudendal nerve fibers can evoke sustained bladder contractions (SBC) in cats, yet evidence of therapeutic efficacy in human subjects is lacking. This pre-clinical study was under-taken to test the hypothesis that robust bladder contractions can be generated with a minimally-invasive needle electrode. Materials and Methods: In seven adult cats, triggered electromyographic (EMG) signals from the external anal sphincter (EAS) were used to minimize the needle-to-nerve distance; while reflex bladder contractions were recorded as 20-sec trains of current pulses of varying amplitude (threshold to 10 mA) and frequency (1-100 Hz) were applied to the nerve. This stimulation paradigm was repeated at successively greater needle-to-nerve distances (0.5 cm intervals) and also at different electrode positions along the nerve. Results: Electrophysiological access to the pudendal nerve was consistently achieved, as indicated by the average threshold for EAS activation (0.31 +/- 0.19 mA). Using different combinations of stimulus amplitude and frequency, robust SBCs were evoked in every experiment. More rostral electrode positions exhibited stimulation amplitudes and corresponding maximum bladder pressures (0.68 +/- 0.36 mA and 25.3 +/- 3.5 cmH(2)O, respectively) that were comparable to those of more invasive stimulation methods. Conclusions: The needle electrode provides a minimally-invasive approach that will enable the study of reflexes mediated by pudendal afferents in humans, and allow pre-operative testing before implanting a permanent device.