Trial Time for Percutaneous Nerve Evaluation in Patients Undergoing Sacral Neuromodulation for Urgency Urinary Incontinence or Urgency-frequency: a Randomized Control Trial

Sacral neuromodulation (SNM) is a minimally invasive procedure that provides low-amplitude electrical stimulation to the S3 nerve root to improve micturition and defecation. It is FDA-approved for the treatment of urgency urinary incontinence (UUI) refractory to behavioral modifications and/or oral medication. The efficacy of SNM for the treatment of UUI is well studied and currently, there are two manufacturers of SNM devices within the United States: Medtronic and Axonics. Both offer rechargeable and non-rechargeable devices.

Patients who elect to proceed with SNM undergo a trial phase to determine therapeutic response prior to placement of a permanent implantable pulse generator (IPG). A trial phase can be performed in two ways: a percutaneous nerve evaluation (PNE) or staged implantation. PNE involves the placement of a temporary wire connected to an electrode using external stimulation. It is performed in the office using local anesthesia. If the patient displays adequate improvement in symptoms (defined as >50% improvement of symptoms from baseline), a permanent lead and subcutaneous IPG are implanted in the operating room. The staged approach involves two separate procedures performed in the operating room: stage I and stage II. Stage I is the clinical trial of the permanent lead with electrodes using external stimulation. Following adequate response, stage II is performed and involves the IPG placement.

PNE offers significant advantages compared to a staged implantation. A PNE is performed in the office under local anesthesia mitigating the anesthetic risk and number of operating room visits. PNE is also suspected to be cost-effective given it is performed in the office with minimal medical equipment; however, this has not been well studied. Full implantation rates are 40-50% following PNE versus 70-90% in women who undergo a staged approach. The lower rate of progression to full implantation with PNE can be attributed to several factors including lead migration. The monopolar PNE lead does not have a self-retaining component like the quadripolar tined lead used during a stage approach. Newer registry data suggest up to 90% of PNE trials lead to full implantation. Authors hypothesize the improved full implantation rates in the newer studies may be secondary to shorter trial times and improved anatomic knowledge.

The trial phase is the most valuable tool to predict therapeutic success of SNM for women with UUI. Several large, multicenter trials support that PNE and staged trial can predict patients who are likely to respond to SNM therapy and experience long term benefits. Literature is limited regarding recommended length of time for the trial phase. The International Continence Society best practice statement for use of SNM currently recommends 7-day trial for women with UUI. However, one study reported high sensitivity and specificity of PNE with a trial time of 3-5 days. This cross-sectional study was limited to a single institution and included patients with nonobstructive urinary retention.

Given the risk of lead migration with PNE, the investigators hypothesize that shortening the trial phase to 3 days will not decrease the proportion of patients who progress onto full SNM implantation. The investigators believe that shortening the window to capture therapeutic response will have several important patient benefits and reduce the chance of lead migration without adversely impacting outcomes. Therefore, the investigators aim to perform a multi-center, randomized trial to determine if a 3-day PNE trial is not inferior to a 7-day PNE trial with respect to rates of progression to full SNM implantation.