Neurogenic detrusor overactivity (NDO) is a chronic and debilitating condition commonly associated with spinal cord injury (SCI) and multiple sclerosis (MS). Intra-detrusor Onabotulinum toxin-A is an established second-line therapy for patients who do not respond to anticholinergics; however, because NDO is a lifelong condition requiring sustained management, the long-term outcomes, durability of repeated injections, and discontinuation rate remain important to clarify (1).

This systematic review followed PRISMA guidelines and Cochrane methodology. Searches of PubMed, Scopus, Cochrane, and Wiley were conducted starting from March 5, 2026 (Figure 1.). Relevant outcomes from the eligible studies were frequency of urinary incontinence (UI) episodes, urodynamic parameters, duration of therapeutic effect, quality of life (QoL), and discontinuation rate. Both randomized trials and observational studies were included (Table 1.). Risk of bias was assessed using the Newcastle–Ottawa Scale for cohort studies, Cochrane RoB 2.0 for randomized trials, and the JBI checklist for case series.

Fifteen studies met the inclusion criteria. Repeated Onabotulinum toxin-A injections produced sustained reductions in UI, with daily leakage episodes typically decreasing by 3–4 episodes per day and remaining stable across reinjection cycles (2). Urodynamic improvements, including increased maximum cystometric capacity (MCC), increased reflex volume (RV), and reduced maximum detrusor pressure (MDP), were consistently maintained over long-term follow-up, with no evidence of declining bladder compliance or treatment-related fibrosis. The duration of therapeutic effect remained stable at approximately 9–11 months (3). QoL improvements were rapid and durable, frequently exceeding 2.5–3 times the minimally important difference (MID). Discontinuation rates varied widely (3.7–41.9%), with most attributed to non-clinical or logistical factors rather than treatment failure; true secondary nonresponse was rare.

Repeated intra-detrusor Onabotulinum toxin-A injections offer durable clinical, urodynamic, and QoL benefits for patients with NDO with no progressive loss of effect over time.

These findings on long-term outcomes and discontinuation rates support its use as a reliable long-term therapy. Further high-quality, standardized long-term trials are needed to refine optimal dosing and reinjection protocols.

Zhou Z, Wang X, Li X, Liao L. Detrusor relaxing agents for neurogenic detrusor overactivity: a systematic review, meta-analysis and network meta-analysis. BJU Int. 2024;133(1):25-33. doi:10.1111/bju.16142
Rovner E, Kohan A, Chartier-Kastler E, et al. Long-Term Efficacy and Safety of OnabotulinumtoxinA in Patients with Neurogenic Detrusor Overactivity Who Completed 4 Years of Treatment. J Urol. 2016;196(3):801-808. doi:10.1016/j.juro.2016.04.046
Grosse J, Kramer G, Stöhrer M. Success of Repeat Detrusor Injections of Botulinum A Toxin in Patients with Severe Neurogenic Detrusor Overactivity and Incontinence. Eur Urol. 2005;47(5):653-659. doi:10.1016/j.eururo.2004.11.009