Minimally-invasive electrical stimulation of the pudendal nerve: a pre-clinical study for neural control of the lower urinary tract.
OBJECTIVE
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 undertaken to test the hypothesis that robust bladder contractions can be generated with a minimally-invasive needle electrode.


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 cmH2O, 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.
Yoo
Paul B
PB
Neural Prosthesis Research Laboratory, Department of Biomedical Engineering, Duke University, Durham, North Carolina.
Grill
Warren M
WM
Neural Prosthesis Research Laboratory, Department of Biomedical Engineering, Duke University, Durham, North Carolina.
D000818:Animals; D002415:Cats; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation; D004566:Electrodes; D005260:Female; D008297:Male; D010525:Peripheral Nerves / Q000502:physiology*; D014546:Urinary Catheterization; D014551:Urinary Tract / Q000033:anatomy & histology / Q000294:innervation*; D014553:Urinary Tract Physiological Phenomena