In a pilot study, Marcelissen et al (2011) examined if bilateral sacral nerve stimulation can be effective to restore treatment efficacy in patients in whom unilateral sacral neuromodulation fails. Patients in whom unilateral sacral neuromodulation failed were included in analysis. The percutaneous nerve evaluation test was used to evaluate the effect of contralateral and bilateral stimulation. The stimulation electrode was placed in the contralateral S3 foramen and symptoms were self-recorded using a 3-day voiding diary. Clinical success was defined as more than 50 % improvement in at least 1 relevant voiding diary parameter versus baseline. The 15 study patients underwent test stimulation with percutaneous nerve evaluation. In 3 patients lead migration was suspected and, thus, they were not included in analysis. Four of the remaining 12 patients had a successful response to percutaneous nerve evaluation, of whom 3 were eventually implanted with a contralateral lead. After 12 months of treatment 2 of the 3 patients had a successful outcome. The authors concluded that only a select group of patients appeared to benefit from bilateral stimulation after unilateral therapy failure. They stated that further investigation is needed to determine the predictive factors and cost-effectiveness of this treatment.