Sacral neuromodulation (SNM) is a treatment for various lower urinary tract and bowel dysfunctions, such as overactive bladder, urinary retention, fecal incontinence, and constipation. Although SNM can be effective for many patients, some may experience failure or suboptimal outcomes. Understanding the factors contributing to SNM failure can help tailor treatment plans and manage expectations. In this study, we examined the factors associated with SNM failure.

This retrospective cohort study involves patients who underwent sacral neuromodulation insertion or revision between 2020 and 2024 at a single, high-volume tertiary hospital. The medical records of included patients were reviewed for demographic data, diagnosis, complications, management of complications, additional therapy rate, and outcomes with a follow-up duration of up to 28 years. We excluded patients with less than six months of follow-ups, patients who lost their follow-up appointments, and those who had failed stage one SNM.

Of 289 patients who underwent insertion or revision of SNM, 257 were included in our study. The majority were female (201; 78%) with an average age of 61±13.6 years. 42% of our patients were obese (110; 42%, BMI>30) with an average BMI of 29.6±6.6. 51.4% of them were suffering from overactive bladder (OAB), 18.7% chronic urinary retention, and 12.5% Interstitial cystitis/painful bladder syndrome. The failure rate of SNM in our patients was 22.6%.
We found that the average age was higher in the SNM failure group (65.9±12.0; p=0.006). Conversely, the average BMI is almost the same in patients with successful and failed SNM treatment (29.7±7.3; p=080). Patients with failed SNM experienced more voltage usage with an average of 2.1±1.13. However, that was not statistically significant (p=.095). The failure rate was higher in patients with frequent reprogramming by 71.4%; p<.001. Experiencing infection or pain at implantable pulse generator (IPG) during the SNM treatment has been correlated with a higher failure rate (p<.001).

Inserting sacral neuromodulation on the contralateral side in patients who have lost efficacy over time has been associated with a higher success rate, whether using two devices simultaneously or only one at a time (95-100%; p<.001). Also, having lead migration followed by revision of the lead helped by increasing the success rate (94%; p<.05).

In our study, 22.6% of 257 patients experienced failure of SNM treatment. We found that the average age was higher in the SNM failure group. Conversely, the average BMI is almost the same in patients with successful and failed SNM treatment. Having an infection, frequent reprogramming, or pain at the implantable pulse generator (IPG) during the SNM treatment has been correlated with a higher failure rate. Inserting SNM on the contralateral side in patients who have lost efficacy over time has been associated with a higher success rate, whether using two devices simultaneously or only one at a time. Also, having lead migration followed by revision of the lead helped by increasing the success rate.

Pain at the site of IPG, infection, elderly status, and frequent reprogramming were found to be common in patients with failed SNM treatment. It is important to note that while these factors do not necessarily indicate that SNM will be ineffective for all patients, they may increase the risk of treatment failure. Therefore, they should be thoroughly considered when assessing patients with SNM.