Pudendal Nerve Mapping Towards Improved Neuromodulation for Urinary Retention

The primary outcome measure in this study was an evoked bladder contraction of at least 20 centimeters of water (cmH2O) during the cystometrogram. These bladder contractions were evoked by applying nerve stimulation to the pudendal nerve through testing of the participant's implanted stimulator. Measure reflects number of participants who experienced an evoked bladder contraction of at least 20 centimeters of water during nerve stimulation.

Time frame: Visit 4, approximately 10 weeks after consent

Population: Due to scheduling conflicts and participant attrition, only 10 participants completed this part of the study. All were women.

A secondary outcome measure was a goal to examine the effect of selective pudendal nerve stimulation on urethral leak point pressure during the cystometrogram.

Time frame: Visit 4, approximately 10 weeks after consent

Population: Selective pudendal nerve stimulation was not performed during the cystometrogram sessions due to time limitations within experimental sessions, so there is no data available. Selectivity could not be accomplished as it was described in the protocol for this nerve bundle.

Selectivity refers to the degree in which a nerve could be stimulated without stimulating other nerves. SI was calculated for each sensor recording from locations innervated by distal pudendal nerve branches during the visit-2 implant procedure. This includes pressure sensors in the urethra innervated by the perineal nerve and anal electromyography (EMG) innervated by the ischeal rectal nerve. The SI calculation used here is on a scale of 0 to 1, with 0 indicating no response at all from the nerve. The closer the number is to 1, the more selective the nerve stimulated.

Time frame: Visit 2: Stage-1 (approximately 3 weeks after consent)

Population: Data was collected from 16 participants who received the implant.

Selectivity is the degree to which part of a nerve could be stimulated without stimulating other nerve parts. For each participant who had successful MRI and CT images, a computational model was created to simulate electrical stimulation of axons distributed in two primary pudendal fascicles: perineal and rectal. The SI of stimulation does not indicate a positive or negative result in this outcome; rather, it shows the relative potential for activating just a single nerve fascicle. The negative/positive designation identifies the regional nerve activation, with -1 representing only perineal fascicle activation, +1 representing only rectal activation, and 0 indicating equal activation of both fascicles.

Time frame: Approximately one year and four months after consent

Population: Computational models were created for 10 participants who received the implant. The model data was segregated into three groups: participants with selectivity indices positive (\>0) for all four contacts (rectal only), negative (\<0) for all four contacts (perineal only), and mixed (both \>0 and \<0). Each group has the same potential range for SI values: -1 to +1. Values in the Outcome Measure Data Table are calculations across all lead contacts and participants per group.