Clinical and Urodynamic Predictors for Sacral Neuromodulation Outcomes in Patients With Overactive Bladder: A Cohort Study

1.0 Introduction: Overactive bladder syndrome (OAB) is a prevalent disorder that affects about 10% of the adult population and > 40% of elderly. It is defined by the presence of urgency, with or without urge incontinence, in the absence of infection or other pathology. In 1997 through 1999, sacral nerve stimulation SNS (InterStim, Medtronic Inc., Minneapolis, Minnesota) was approved by the U.S. Food and Drug Administration (FDA) for treating urge urinary incontinence, urinary urgency, and frequency. Despite the large numbers of SNS performed, the only objective clinical evaluation of OAB is urodynamic detrusor instability (UDI) with some evidence suggesting a correlation with outcomes after sacral neuromodulation.

Interestingly, the mechanism of action of SNS is not fully understood. Theories include direct activation of efferent fibers to the striated urethral sphincter causing reflex relaxation of the detrusor or potential activation of afferent fibers selectively which can lead to inhibition at spinal and supraspinal levels. Somatic sacral afferent inflow activation at sacral level affects the storage and emptying reflexes in the bladder and central nervous system, explaining the beneficial effects of neuromodulation on both storage and emptying functions of the bladder. Malaguti and his colleagues detected somatosensory evoked potentials during sacral neuromodulation, revealing that sacral neuromodulation works by both sacral afferent activity and somatosensory cortex activation. As sacral neuromodulation is clinically proven for both storage and emptying bladder dysfunctions, it is difficult to isolate its action to either sacral afferent or efferent circuits in the micturition reflex pathway. In our study, we are going to study sacral neuromodulation outcome predictors from the clinical and urodynamic perspectives in order to help identifying the right candidates for sacral neuromodulation procedure.

2.0 Specific Aims:

• Specific aim#1: Using the medical reporting systems, we will identify all patients who, underwent sacral neuromodulation at University Hospitals of Cleveland from January 1, 2012 through February, 2017.
• Specific aim#2: Reporting on the efficacy outcomes including: rate of successful placement, rate of reported patient improvement after peripheral nerve (PNE) stage 1 and stage 2 procedure. The proportion of patients who undergo stage 2 compared to patients who had PNE. Rate of removal after full implantation and rate of battery change. Finally, will report on patient satisfaction, change in disease-specific severity scores and change in health-related quality of life
• Specific aim #3: Will identify preoperative clinical and urodynamic factors that can predict successful outcome and or/ failure.
• Specific aim #4: to identify predictors in subgroups of patients with OAB including:

1. Wet versus dry subgroups.
2. With urodynamic detrusor instability (UDI) versus no UDI subgroups.
3. Neurogenic versus non-neurogenic.
4. Staged versus non-staged procedure.

• Specific aim #5: Validating the identified predictors in a different established set of patients from Cleveland Clinic.
• Specific aim#6: Reporting on safety outcomes including intraoperative complications, early postoperative complications (within 30 days) and later postoperative complications. A modified Dindo classification will be utilized.