Therapeutic effect of urethral sphincter onabotulinumtoxinA injection for urethral sphincter hyperactivity.

ABSTRACT

PURPOSE: Urethral sphincter hyperactivity resulting in voiding dysfunction is frequently encountered. Medical treatment might not achieve a satisfactory result. OnabotlinumtoxinA urethral sphincter injection relaxes sphincter tonicity and possibly resumes efficient voiding. This study analyzed the treatment outcomes and predictor for successful onabotulinumtoxinA treatment on these patients. METHODS: Patients with voiding dysfunction due to urethral sphincter hyperactivity and treated with injections of 100 U onabotulinumtoxinA into the urethral sphincter were retrospectively reviewed. Treatment outcomes were assessed 1 month after injection using the Global Response Assessment and were analyzed by demographic and baseline video-urodynamic characteristics. RESULTS: Of the 95 patients included, satisfactory outcomes were reported in 58 (61.1%) patients. Treatment outcome was not related to age, gender, or voiding dysfunction subtype. Patients with satisfactory outcomes had a significantly smaller volume at first sensation of filling (P = 0.046), greater detrusor pressure (P = 0.027), higher maximum flow rate (P = 0.017), and smaller post-void residual (P = 0.006). In multivariate analysis, an open bladder neck during voiding was the only predictor for successful outcome (88% in satisfactory outcome, 12% in failure outcome, P < 0.001). Patients with non-neurogenic voiding dysfunction had a significantly longer therapeutic duration than those with neurogenic voiding dysfunction (9.55 ± 4.18 vs 7.44 ± 2.91 months, P = 0.033). Increased urinary incontinence was reported in 18 patients, including 6 with stress urinary incontinence and 12 with urgency urinary incontinence. CONCLUSION: Subjective improvement was reported in 61.1% of patients with voiding dysfunction due to urethral sphincter hyperactivity after onabotulinumtoxinA urethral sphincter injection. An open bladder neck during voiding at baseline predicts a successful outcome.