Does response to percutaneous tibial nerve stimulation predict similar outcome to sacral nerve stimulation?

AIMS: Percutaneous tibial nerve stimulation (PTNS) is a simple neuromodulation technique to treat an overactive bladder. It is unclear whether the response to PTNS would suggest a similar response to sacral nerve stimulation (SNS), and whether PTNS could be utilized as an alternative test phase for an SNS implant. This study assessed whether PTNS response was a reliable indicator for subsequent SNS trials. METHODS: We performed a retrospective review of the hospital databases to collect all patients who had PTNS and who subsequently had an SNS trial in two tertiary hospitals from 2014 to 2020. Response to both interventions was assessed. A 50% reduction in overactive symptoms (frequency-volume charts) was considered a positive response. McNemar's tests using exact binomial probability calculations were used. The statistical significance level was set to 0.05. RESULTS: Twenty-three patients who had PTNS subsequently went on to a trial of SNS. All patients except one had previously poor response to PTNS treatment. Eight of them also failed the SNS trial. However, 15 patients (including the PTNS responder) had a successful SNS trial and proceeded with the second-stage battery implantation. The difference in response rates between the PTNS and SNS trial was statistically significant (p < 0.001). CONCLUSIONS: Poor response to PTNS does not seem to predict the likelihood of patients responding to SNS. A negative PTNS trial should not preclude a trial of a sacral nerve implant. The predictive factors for good and poor responses will be the subject of a larger study.

Predicting a successful outcome in sacral neuromodulation testing: Are urodynamic parameters prognostic?

AIMS: To assess whether the urodynamic parameters of mean voided volume, peak detrusor overactivity (DO) pressure, bladder compliance, capacity, and volume at first detrusor overactivity during filling cystometry can predict a successful outcome at first stage tined lead placement (FSTLP). METHODS: Ninty-nine consecutive patients with urodynamically proven idiopathic detrusor overactivity (IDO) refractory to medical treatment and opting for Sacral Nerve Stimulation (SNS), were assessed pre and post FSTLP. Data from 3-day frequency-volume charts, and patient reported (subjective) outcomes were used to assess success or failure after FSTLP. Success was defined as improvement in symptoms >50%. Binary logistic regression analysis was used to ascertain whether key parameters at filling cystometrogram were predictors for success prior to FSTLP. RESULTS: Binary logistic regression analysis did not demonstrate any significant relationship between the five parameters at urodynamics and outcome at FSTLP (B < 0.01, P > 0.16) for all parameters. CONCLUSIONS: The results from this prospective analysis on patients with IDO refractive to medical therapy referred for SNS would suggest that aside from proving DO at urodynamics as a pre-requisite for intervention as per NICE and EAU guidelines, no parameter is predictive for a successful outcome at FSTLP.