Peripheral nerve evaluation (PNE) permits a trial of sacral neuromodulation to determine candidates for permanent system implant in a single operation.  Pre-fluoroscopy PNE success rates with unipolar leads are typically quoted at 40-50%, whereas staged procedures with tined quadripolar leads have an estimated 77% success rate [1,2].  With the availability of in-office fluoroscopy and improved technique over time, more contemporary data on PNE success rates appear limited.  This study evaluated a recent series of PNE patients to determine predictive factors toward PNE screening success and persistent functional response following permanent system implant.

A retrospective review of all patients who underwent PNE at a large academic center from 2015-2019 was performed.  All unipolar leads were placed percutaneously in-office under local anesthesia utilizing fluoroscopy by one of four FPMRS fellowship-trained providers.  Patients with refractory urgency-frequency and/or urge urinary incontinence were included, while those with chronic urinary retention were excluded.  Rates of full system implant after successful PNE trial and continued improvement at ≥1-month following permanent implant were reviewed.  Multivariable logistic regression determined predictors of PNE success and continued functional success at follow-up.

102 PNE patients (87 females and 15 males) were included.  Mean age was 65.9 years and BMI was 29.4.  Median ASA score was 3.  Bilateral leads were placed in 95 patients (93.1%).  78 patients (76.5%) were PNE responders (≥50% symptom improvement).  Median postoperative follow-up time was four months following permanent implant.  On multivariate analysis, patient predictors of PNE success included younger age (p=0.014), urge incontinence (p=0.021), fecal incontinence (p=0.017), and absence of a neurologic diagnosis (p=0.04).  PNE factors associated with satisfactory screening included presence of bellows and plantar toe flexion (p=0.038), and perineal sensation (p=0.027) (Table).  68 patients (87.2% of PNE responders [68/78] and 66.7% of all patients [68/102]) had a successful working implant at ≥1-month follow-up.  Absence of a neurologic diagnosis was predictive of persistent implant success on long-term follow-up (p=0.013).

This contemporary series of unselected patients undergoing PNE with fluoroscopy revealed screening success rates (76.5%) equivalent to available reports on staged implant (approximately 77%).  Patient predictors of PNE success included younger age, urge incontinence, fecal incontinence, and absence of a neurologic diagnosis.  PNE testing factors associated with satisfactory screening included presence of bellows and plantar toe flexion, and perineal sensation.  In this broad group of PNE patients, 67% of all patients demonstrated an optimal response following permanent implant at ≥1-month follow-up.  Conversion from successful screening test to permanent implant may not be the ideal outcome and evaluation for persistent improvement should be considered as an indicator of successful screening.

This contemporary series of unselected patients undergoing PNE with fluoroscopy revealed screening rates equivalent to available reports on staged implant.  Patient predictors of PNE success included younger age, urge incontinence, fecal incontinence, and absence of a neurologic diagnosis.  67% of all patients demonstrated an optimal response following permanent implant at ≥1-month follow-up.  We suggest success of the permanent implant be considered when defining PNE "success" rates.

Janknegt RA, Weil EH, Eerdmans PH. Improving neuromodulation technique for refractory voiding dysfunctions: two-stage implant. Urology. 1997 Mar;49(3):358-62.
Spinelli M, Weil E, Ostardo E, et al. New tined lead electrode in sacral neuromodulation: experience from a multicenter European study. World J Urol. 2005 Jul;23(3):225-9.