BoNT-A injection has been widely used in treatment of neurogenic or non-neurogenic detrusor overactivity refractory to antimuscarinic therapy. Patients with neurogenic detrusor sphincter dyssynergia (DSD), non-neurogenic dysfunctional voiding (DV), or detrusor underactivity (DU) with an open bladder neck have also been treated by urethral sphincter BoNT-A injection. However, clinical researches of the efficacy of BoNT-A injection on the BND are limited. This study retrospectively analyzed the treatment outcome of BoNT-A injection on BND, and searched for predictive factors for a satisfactory or failed treatment outcome.

A total of 41 patients with different LUTDs received transurethral bladder neck BoNT-A injection for their voiding dysfunction. The patients received videourodynamic study (VUDS) and a tight bladder neck was demonstrated with or without a high voiding detrusor pressure (Pdet) or DO. Bladder neck BoNT-A injection was performed under intravenous general anesthesia. A total of 100U of BoNT-A dissolved in 5ml of normal saline was injected at 5 sites of the bladder neck. The treatment outcome was assessed by self-reported global response assessment (GRA) for the improvement of voiding efficiency and difficulty. The treatment outcome was assessed by self-reported global response assessment (GRA, scored from -3 to +3, indicating from got worse to excellent) for the improvement of voiding efficiency and difficulty.

A total of 41 patients (33 men and 8 women) who had VUDS proven BND received bladder neck 100U BoNT-A injection for the voiding dysfunction. The mean age was 43.6 ± 17.1 (4 – 74) years. Among the patients 35 (85.4%) had normal detrusor contractility and 6 (14.6%) had DU or DA. At 6 months after the BoNT-A injection, 11 (26.8%) patients had a successful treatment outcome, 16 (39.0%) had an improved outcome, and 14 (34.1%) failed the treatment. The overall satisfactory rate was 65.9% at 6-month follow-up.  Analysis of the baseline VUDS parameters, the patients with non-neurogenic BND had the highest satisfactory outcome (81.8%), whereas patients with neurogenic BND had a lower satisfactory outcome (50% for NBND and 55.6% for NBND plus DSD). (Table 2). Patients with normal detrusor contractility and a failed treatment outcome had a higher BOO index than those with a satisfactory treatment outcome (52.5 ± 30.8 vs. 27.7 ± 23.8 cmH2O, p = 0.047). (Table 2). Logistic regression analysis revealed that a higher PVR at baseline predicts a failed treatment outcome of BoNT-A BN injection for patients with BND. However, the p value is only marginal (p = 0.053). (Table 3)

This study investigated the clinical efficacy of bladder neck BoNT-A injection in treating NBND and non-NBND. The findings indicate that patients with non-NBND achieved the highest rate of satisfactory outcomes (81.8%), whereas those with NBND exhibited lower response rates. Moreover, in patients with normal detrusor contractility, treatment failure was associated with a significantly higher BOO index compared to those with successful outcomes. Additionally, logistic regression analysis suggested that a higher PVR volume at baseline may predict an unsuccessful treatment outcome, although this finding reached only marginal statistical significance (p = 0.053). These results suggest that although BND was evident in VUDS, other urethral dysfunctions such as DV and DSD might coexist with BND and result in a failure treatment of bladder neck BoNT-A injection treatment.

Only 26.8% of patients had a successful treatment outcome, 39.0% had an improved outcome, and 34.1% failed after bladder neck BoNT-A injection for treatment of BND associated voiding dysfunction. Patients with a high Pdet at baseline and those with spinal cord injury and DSD might have a less favorable outcome after treatment.

Jiang YH, Chen SF, Kuo HC. Role of videourodynamic study in precision diagnosis and treatment for lower urinary tract dysfunction. Tzu Chi Med J. 2019 Nov 18;32(2):121-130.
Kuo HC. Videourodynamic Precision Diagnosis and Treatment of Lower Urinary Tract Symptoms in Women. Urological Science 32(3):p 94-101, Jul–Sep 2021.
Yu WR, Tian JH, Kuo HC. Efficacy of Urethral Sphincter Botulinum Toxin A Injection in Patients with Spinal Cord Injury with Dysuria: A Retrospective Cohort Study. Toxins (Basel). 2024 Jul 31;16(8):336.