**4. Conclusions**

The urethral sphincter BoNT-A injection is effective in treating voiding dysfunction in non-SCI patients. The results of this study showed that patients with DV may benefit the most in terms of subjective and objective parameters, whereas those with DU and PRES also have a fair response in approximately half of the patients. PVR > 250 mL may indicate a poor treatment outcome in patients with DU.

## **5. Materials and Methods**

This study retrospectively analyzed patients with voiding dysfunction who were refractory to medical treatment. They received 100 U of BoNT-A injection (onabotulinumtoxinA, Allergan, Irvine, CA, USA) via urethral sphincter by cystourethroscope. All patients underwent videourodynamic study (VUDS) assessments to identify the underlying etiology of the lower urinary tract dysfunction before administering BoNT-A injections. Patients with anatomical BOO of various etiologies, such as urethral stricture, bladder neck obstruction, or benign prostatic hyperplasia, were excluded from the study. SCI patients with DSD were also excluded. Finally, patients with DU who required abdominal straining for spontaneous voiding and those who required urethral sphincter non-relaxation while voiding were included in the final analysis. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ethics Committee of Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation (IRB 111-247-B), and waived informed consent due to its retrospective nature.

The urethral BoNT-A injection treatment was performed under light intravenous general anesthesia. A total of 100 U BoNT-A was given via transurethral sphincter injections per our previous report [24]. One vial of 100 U botulinum toxin A was reconstituted with normal saline to 5 mL. Every one mL of BoNT-A solution was injected into the urethral sphincter at the 2, 4, 6, 8, and 10 o'clock positions transurethrally in men. Transcutaneous injections were administered to the urethral sphincter along the urethral lumen at the 2, 4, 6, 8, and 10 o'clock positions of the sides of the urethral meatus in women. A Foley catheter was placed overnight after BoNT-A injections and removed the next morning. Self-voiding status was recorded at the outpatient clinic. In our previous experiences, the effect of BoNT-A on the urethral sphincter's function appeared approximately three days after injection and the maximum therapeutic effect was attained 2 weeks after treatment [24]. Three days of antibiotics were given to prevent UTIs. After BoNT-A injections, we discontinued other medication for reducing urethral resistance.

Baseline VUDS parameters, including the cystometric bladder capacity (CBC), voided volume (VV), PVR, Qmax, first sensation of bladder filling (FSF), first desire (FS), urge sensation (US), bladder compliance, and detrusor pressure at the maximal flow rate (Pdet.Qmax), were recorded. VE was calculated as follows: voided volume/total bladder capacity × 100 [25]. The maximum filling volume was defined if patients consistently had no urge to void at 600mL. Bladder compliance was measured at CBC. The terminology used in this study was based on the recommendations of the International Continence

Society [1]. All patients were regularly followed up at a single center, and repeated VUDS was performed within 6 months. For analysis of the treatment outcome, the urethral sphincter dysfunctions were categorized as DV and PRES, according to the electromyographic reports and pictures during voiding cystourethrography on VUDS. DV was diagnosed when high detrusor pressure, intermittent or increased external sphincter EMG activity, and a "spinning top" urethral appearance on cinefluoroscopy during voiding occurred together. On the other hand, PRES was diagnosed based on low voiding Pdet.Qmax, with non-relaxation of urethral sphincter EMG and narrow urethral during urination.

The primary outcome of this study is the VE after treatment which was assessed after the urethral BoNT-A injection to report their global response assessment (GRA) by reviewing the patient's chart over 1 month and graded from 0 to 3. Patients who needed indwelling urethral catheters or suprapubic cystostomy (IDC) and clean intermittent catheterization (CIC) and those with a VE of less than 33% were classified as those with treatment failure (grade 0). When patients who were able to urinate (either abdominal straining or spontaneously) with a VE of 33.3–66.7% were considered to have mild improvement (grade 1). Those who could urinate with a VE of 66.7–90% were considered to have experienced moderate improvement (grade 2). If patients could urinate with VE of 90–100% were considered to have experienced marked improvement (grade 3). Patients who could achieve grade 2 or 3 improvements after treatment were considered to have satisfactory outcomes. For recording the VE, patients were asked to urinate at a strong/urgent desire to the uroflowmetry. If voided volume plus PVR was less than 250 mL, patients were requested to urinate again. The secondary endpoint is the VUDS parameters before and 6 months after treatment. Adverse effects after BoNT-A injections were also recorded.
