Primary bladder neck obstruction (PBNO) is a type of functional bladder outlet obstruction defined by inadequate bladder neck opening when voiding seen at video urodynamics. Causes for PBNO is not well understood but may relate to sympathetic nervous system dysfunction or muscular abnormalities of the external urethral sphincter (1). 

Treatment aims to reduce bladder neck resistance, with the mainstay options being alpha-blocker therapy and bladder neck incision (BNI). Although data on the use of Botulinum Toxin A (BoNTA) in this population is limited to few small studies, these show promising results (2,3).  However, not much is known about progression of these patients to further treatments such as repeat BoNTA and definitive BNI.

This study aims to report on the outcomes of bladder neck injection of BoNTA in males and females diagnosed with PBNO at two participating institutions.

Retrospective data from two participating centres was collected and reviewed from May 2011 to May 2018. Inclusion criteria included all patients with a diagnosis of PBNO based on urodynamic findings with fluoroscopy or ultrasound and underwent cystoscopy with injection of BoNTA into the bladder neck

Surgical technique
Under general anaesthesia or spinal anaesthesia, patients were place in lithotomy, a single dose prophylactic cephalosporin or quinolone was given. Pressure points were padded to avoid any neuropraxia. 100 units of Onabotulinum toxin A (Botox ®, Allegan, Irvine, CA) in 4 ml of normal saline (25 U/mL) was injected transurethrally at four sites of bladder neck at 3, 6, 9 and 12 o’clock using the rigid cystoscope and a 23 gauge Cook ® William’s needle. Dose adjustments were made on subsequent treatments dependent on patients response and clinicians clinical judgement.

During the 7-year study period, 13 patients with a diagnosis of PBNO underwent bladder neck injection of BoNTA. The median age was 40 (IQR 30-46). There were 5 men (38.5%) and 8 women (61.5%) in this case series. Of the 11 patients who could void at the time of urodynamics study, the median Qmax was 14 ml/s (IQR 3-16). Pre-operatively, five patients had significant urinary retention due to PBNO, of which four patients were managed with intermittent self catheterisation and one patient with suprapubic catheterisation. Nine patients had tried alpha blockers prior to bladder neck BoNTA injection. 

One patient was lost to follow-up after the bladder neck BoNTA. Of the remaining 12 patients, subjective improvement was observed in nine patients (75%) and three patients did not have any change in symptoms (25%). Six of the nine patients with improvement in symptoms returned a questionnaire on a Likert scale of 0 to 10, and reported a median improvement of 8 (IQR 7-9).Follow up and further treatments are summarised in Figure 1.

7 patients had 2nd BoNTA injection, median interval time 7.4 months (IQR 6.4-12.3), 4 patients underwent a 3rd  BoNTA injection, median interval time 9.2 months, 2 patients underwent a 4th BoNTA injection, at 12 and 17.7 months from their last treatment.
The same 2 patients had a 5th injection BoNTA, at 10.3 and 9.7 months from their last treatment. 3 patients eventually proceeded to BNI

In this small case series, we found that bladder neck injection of BoNTA may be useful to treat patients with PBNO who are either refractory or intolerant to alpha-blockers with a 75% subjective improvement response rate. These are comparable to previous studies in the field.

BoNTA treatment may be a useful prognostic tool in patients with PBNO to determine the likelihood of symptom response to bladder neck incision which is a permanent and irreversible procedure. Further randomised and prospective trials are required to investigate the role of bladder neck BoNTA in PBNO.

Aggarwal H, Lemack GE. Primary Bladder Neck Obstruction in Men and Women: an Update on Diagnosis and Management. Cur Bladder Dysfunct Rep. 2015;10(3):288-94.
Sacco E, Tienforti D, Bientinesi R, D'Addessi A, Racioppi M, Pinto F, et al. OnabotulinumtoxinA injection therapy in men with LUTS due to primary bladder-neck dysfunction: Objective and patient-reported outcomes. Neurourol and Urodyn. 2014;33(1):142-6.
Lim SK, Quek PL. Intraprostatic and bladder-neck injection of botulinum A toxin in treatment of males with blacdder-neck dyssynergia: a pilot study. Eur Urol. 2008;53(3):620-5.