Botulinumtoxin A (BoNT-A) injections into the external urethral sphincter (EUS) is an established therapeutic procedure to reduce bladder outlet obstruction in neurogenic patients with detrusor-sphincter-dyssynergia (DSD) due to spinal cord injury (SCI). Given the paucity of data in patients with DSD but without SCI, we aimed to assess the efficacy of transperineal electromyography (EMG) directed EUS injections with BoNT-A in a cohort of patients with suprapontine cerebral lesions.

For this retrospective study, we screened all patients who underwent their first BoNT-A injection into the EUS at the clinic for neurorehabilitation and paraplegiology in Basel between 2015 and 2021. Inclusion criteria were patients aged 18 years or older with neurogenic detrusor overactivity (NDO) and DSD with a maximum detrusor pressure (Pdetmax) during voiding of at least 40 cmH2O, confirmed by urodynamic studies (UDS). Of these, patients with SCI were excluded. Primary outcomes were a reduction in Pdetmax during voiding and post-treatment detrusor overactivity leak point pressure (DOLPP). Secondary outcome was a reduction of patients relying on indwelling urinary catheters post-treatment.

Our retrospective chart analysis revealed 13 eligible male patients (median age 31 years), with different underlying suprapontine disorders (traumatic brain injury = 6, hypoxic/septic encephalopathy = 3, other = 4). All patients underwent transperineal EMG triggered BoNT-A injections into the external urethral sphincter with rectal finger guidance. Patients received either 100 (n = 7) or 150 (n = 6) units, respectively. Pdetmax during voiding was significantly lower post-BoNT-A (median 105 vs. 54 cmH2O, p=0.006) and also voided volume during reflex micturition rose significantly (median 120 vs. 220 ml, p<0.05), whereas DOLPP remained unchanged (median 50 vs. 50 cmH2O, p = 0.33). While 6 patients relied on an indwelling urinary catheter pre-treatment, no patient required an indwelling urinary catheter post-treatment.

Our results demonstrate the feasibility and the reliable technique of transperineal BoNT-A injections into the external urethral sphincter in male patients. No complications occurred in our series. In this cohort of patients with NDO and DSD without underlying SCI the reduction in Pdetmax during voiding as the primary outcome of the study was significant. This is of particular importance as it means a risk reduction for upper urinary tract deterioration in these patients. On the other hand, pre- and post-treatment urodynamics did not show a change in detrusor overactivity leak point pressure (DOLPP) what cannot be easily interpreted. We observed a discrete reduction of pressure range and also a reduction of upper and lower quartiles, but without significance. We consider a lack of precision in our injection technique as a possible explanation for this finding that gives room for further improvement. The secondary outcome was also achieved as no patient further relied on indwelling urinary catheters post-treatment what is particularly satisfying from a clinical perspective.

Transperineal BoNT-A injections into the external urethral sphincter in male patients with NDO and DSD without underlying SCI is feasible and significantly reduces bladder outlet obstruction in this cohort.