**8. Conclusions**

In recent decades, BoNT-A has been used in the treatment of VD caused by various types of USD. It has been reported to be effective in the management of DSD, DV, PRES, and has shown promise in treating FS. However, patient satisfaction might not correlate well with objective improvement. BoNT-A injections may serve as a less invasive and safer option in treatment of USD refractory to conventional medications. The mechanism by which BoNT-A improves USD is thought to be a result of a decrease in urethral resistance via inhibition of acetylcholine released in the presynaptic neuron of the EUS, and through the recovery of detrusor muscle contractility via neuromodulation. Studies focused on BoNT-A injections at the EUS have often been limited to distinct etiologies of USD. Further well-designed clinical and basic studies are needed to confirm its effect.

**Author Contributions:** Conceptualization, H.-C.K.; Investigation, Y.-C.O., Y.-L.K., & K.-H.H.; Project administration, Y.-L.K., Y.-C.O., & K.-H.H.; Supervision, Y.-C.O. & Y.-L.K.; Visualization, Y.-L.K. & Y.-C.O.; Writing—original draft preparation, Y.-C.O. & Y.-L.K.; Writing—review and editing, Y.-L.K., Y.-C.O., & H.-C.K.

**Funding:** The work was supported by grants from National Cheng Kung University Hospital (NCKUH-10803011).

**Acknowledgments:** The work was greatly enhanced by the assistance of Yung-Ming Lin.

**Conflicts of Interest:** The authors declare no conflict of interest.
