Variable frequency stimulation of sacral neuromodulation in black-zone overactive bladder patients: a case report

Overactive bladder (OAB) is a common urological disease, reducing patient quality of life (QoL). Sacral neuromodulation (SNM) is a treatment option used when conservative treatment is inadequate. However, constant frequency stimulation-SNM (CFS-SNM) may not be sufficiently effective in achieving targeted symptom reduction in some patients. For such black-zone patients, a different treatment strategy is needed. Variable frequency stimulation (VFS) has been used for deep-brain stimulation treatment in patients with Parkinson's disease with positive outcomes. Accordingly, in this study, we hypothesized the promising outcomes of VFS-SNM in black-zone OAB patients. Here, we evaluated the efficacy and safety of VFS-SNM viz-a-viz CFS-SNM in a black-zone patient with refractory OAB whose frequent micturition symptoms were not relieved after undergoing traditional conservative treatment. A 50-year-old male patient was treated with CFS-SNM at our hospital in October 2016, but his symptoms recurred after administering multiple medications and program-controlled parameter adjustments. We then treated the patient with VFS-SNM in March 2020. A 2-week follow-up through telephonic interviews was conducted; the improvements in voiding symptoms were evaluated by calculating the OAB symptom score (OABSS) and OAB-related QoL (OAB-QoL) score. We observed that OABSS was significantly lower after VFS-SNM than after CFS-SNM. Further, we observed that VFS-SNM significantly improved daytime and nocturnal micturition frequency, as evident from the reduced OABSSs from after CFS-SNM to after VFS-SNM. The main reason for patient dissatisfaction after CFS-SNM was the increased average daily micturition frequency and urgency. VFS-SNM controlled the micturition frequency to within the patient's acceptable range, significantly improving the patient's QoL (40% improvement in OAB-QoL score). To the best of our knowledge, this is the first case report on the use of VFS-SNM with positive outcomes in a black-zone OAB patient, suggesting that VFS-SNM is not inferior to CFS-SNM in the treatment of black-zone patients.