Effect on sensory and motor parameters of a first intradetrusor botulinum neurotoxin A injection in patients with neurogenic bladder: A retrospective study.

BACKGROUND: Overactive bladder (OAB) is common in suprasacral neurological disorders and often associated with detrusor overactivity (DO). Botulinum neurotoxin A (BoNT-A) is a second-line treatment inducing reversible chemical denervation. While its motor effects are well documented, its impact on sensory parameters in neurogenic bladder dysfunction remains poorly understood.

AIM: To evaluate sensory and motor bladder changes following BoNT-A injection in neurogenic DO (NDO).

METHOD: This retrospective single-center study included patients with NDO who received a first BoNT-A injection (from 2015 to 2024). Urodynamic assessments were performed pre- and 2-6months post-injection. Changes in OAB symptoms and urodynamic parameters were analyzed, including sensory (first desire to void [FDV], strong desire to void [SDV]), and motor parameters (DO occurrence, volume at first involuntary detrusor contraction (IDC)).

RESULTS: Among 90 patients (mean age 50.4±15.6years, 61% female, 53 with multiple sclerosis, 35 with spinal cord injury), urgency and urgency urinary incontinence significantly decreased (from 84% to 52% and from 80% to 42%, respectively; P<0.001). DO occurrence declined from 97% to 42% (P<0.001). Bladder sensations (FDV and SDV) persisted in 84% of patients but were significantly delayed.

CONCLUSION: BoNT-A is an effective treatment for neurogenic overactive bladder in multiple sclerosis and spinal cord injury, improving both urgency and urinary incontinence. Its clinical efficacy is associated with resolution of detrusor overactivity, alongside with sensory changes. Preserved but delayed filling sensations after treatment suggests that BoNT-A may modulate afferent signaling. However, whether its clinical benefits are primarily driven by sensory modulation or motor inhibition remains uncertain.