Unilateral versus bilateral sacral neuromodulation in patients with chronic voiding dysfunction

Purpose: Bilateral sacral nerve neuromodulation has been proposed as a more effective treatment for chronic voiding dysfunction. However no comparison with the unilateral approach has been performed. We investigated the possible advantage of bilateral sacral neuromodulation. Materials and Methods: In a prospective randomized crossover trial we investigated 33 patients who underwent bilateral implantation of a temporary test lead. Unilateral and bilateral test stimulation was continued for 4 to 6 days in all patients. Patients were randomly assigned to start with bilateral or unilateral stimulation. Between the stimulation episodes a 2-day washout interval was scheduled. Voiding diaries were completed at baseline and during the entire stimulation period. Sacral x-rays were taken to confirm lead positioning or possible migration after implantation and at the end of the test stimulation period. After 10 days the temporary leads were removed and voiding diaries were analyzed. Results: After stimulation sacral x-ray revealed test lead migration in 8 patients, leaving 12 patients with urge incontinence and 13 with voiding difficulty and urinary retention available for review. A statistically significant improvement in voiding parameters was seen during the test stimulation period. However no statistically significant improvement was seen due to bilateral stimulation compared to unilateral stimulation. Two patients with urinary retention only started voiding to completion during bilateral stimulation. Conclusions: Bilateral is in general not superior to unilateral sacral neuromodulation. However, in some individuals bilateral stimulation may be more effective in relieving symptoms. Therefore, if unilateral percutaneous nerve evaluation falls, a bilateral test should be considered.