Cycling Versus Continuous Mode in Neuromodulator Programming

Background and Significance:

The purpose of this research proposal is to evaluate the effect of cycling versus continuous neuromodulator programming on overactive bladder syndrome. s.In 1997, the Federal Drug Administration (FDA) approved the sacral nerve stimulator as a treatment for refractory urge incontinence. Sacral Neuromodulation works via stimulation of the sacral nerve roots 2-4, (S-2, S-3 and S-4), although the exact mechanism of action is unknown. While implanted electronic stimulators have been used increasingly in the last twenty years, little investigation has documented the actual programming of the stimulator. Prospective trials examining the ideal programming parameters for a specific condition are needed to better identify optimal use of sacral nerve modulation therapy.

In brief, women with overactive bladder who are refractory to treatment are eligible for a trial placement of a neuromodulator. The modulators are placed in two stages; in stage one, a temporary lead is placed in the 3rd sacral foramen. Each neuromodulator has 4 electrodes that are placed via a single lead into the 3rd sacral foramen. The patient will generally return to clinic one week following stage 1 for a post-op evaluation. If the patient reports a 50% improvement in frequency as measured on a 3-day voiding diary, the modulator is permanently implanted. This is stage 2. After placement, the modulator is programmed in the recovery room. Patients are trialed on four set programs for their stimulator. Each program differs in electrode combination, pulse width, amplitude and rate as well as direction of current. Each of the four programs is tested with the patient to determine which is felt by the patient in the perineum and is comfortable. Finally, patients can either have their modulator set on a cycling or continuous mode. Currently, decisions regarding programming are made by whoever is assessing the patient and are not data driven.

Typically, cycling means the neuromodulator stimulation is on for 16 seconds & off for 8 seconds. Continuous means the patient receives constant stimulation. A single retrospective study described program parameters for programming of the modulator for treatment of Over Active Bladder (OAB). It described 67 patients who had good response to neuromodulation, and determined the mean pulse width was 204 microseconds, the pulse width ranged between 120-270 microseconds; the average rate was 9 with a range of 2-20 pulses/second. The majority of women were on cycling mode. Program cycling is purported to decrease the incidence of patients reporting that their modulator is no longer working and thought to extend battery life. No other study has investigated whether or not cycling of the stimulator improves patient outcomes.

Our objective is to compare patient outcomes using in validated symptom measures of OAB between women who are set on cycling versus continuous programs. Investigators propose to perform a randomized crossover study in women who are successfully treated with neuromodulation to either continuous or cycling mode and compare differences between groups on the OAB-q SF symptom questionnaire. The investigators will also compare differences in urinary frequency and pad counts between women randomized to cycling versus continuous stimulation using voiding diaries.