**5.5 Botulinum toxin type A (BT-A)**

BT-A is one of the strongest known toxins. When injected directly into a muscle, it causes flaccid paralysis by blocking the presynaptic release of acetylcholine [66].

The use of BT-A in patients with detrusor sphincter dyssynergia (DSD) was first described by Dykstra et al. [67]. In this study, BT-A was injected into the external urinary sphincter of adult patients with spinal cord injury and DSD. Positive results, reduced urethral pressure, and volume of residual urine remained for an average of 50 days.

Indications for the injection of BT-A in the external urinary sphincter have been extended over time to adult patients with DV and detrusor hypocontractility. In the study by Kuo et al. clinical and urodynamic improvement was registered in 83% of patients with urethral sphincter non-relaxation and detrusor hypocontractility [68]. Petit and co-workers reported a significant reduction in detrusor and urethral pressure, as well as the volume of post-void residual urine after a single injection of 150 units Dysport (BT-A) in patients with spinal cord injury and DSD [69]. The beneficial effects of the therapy lasted for about 2-3 months.

In children treated with BT-A (amp. Dysport) due to spasticity, the most commonly reported adverse effects were local muscle weakness, urinary incontinence, fatigue, somnolence, flu-like symptoms, fever, and rash [70].

BT-A is used in the treatment of DV in children who are resistant to standard urotherapy. In the study of Radojicic et al., BT-A was applied in to the external urinary sphincter in children with DV [71]. The residual urine decreased significantly in 17 of 20 patients after 6 months of follow-up. The authors emphasized that temporary inhibition of the external urinary sphincter and/or PFMs may interrupt the DV cycle. The use of urotherapy during this period could help the child to re-adopt a normal urination pattern and thus reduce the need for re-injections.

In our institution, a prospective clinical study included 9 neurologically healthy girls with DV, aged 3-11 years, who had previously been treated with standard urotherapy without improvement [72]. Application of BT-A (amp. Dysport) in a dose of 500 units was performed transperineally into the external urethral sphincter. After two weeks of application, rehabilitation treatment consisting of standard urotherapy and PFM relaxation exercises was included. Six months after Dysport administration, there was a statistically significant improvement in clinical manifestations (urinary incontinence, voiding difficulties, urinary tract infections), and a significant reduction in post-void residual urine. No significant improvement in uroflowmetry parameters was registered. No children had systemic side effects with Dysport. The authors concluded that the act of urination in children with DV resistant to standard therapy can be significantly improved and maintained for at least 6 months after the use of amp. Dysport and urotherapy.
