Primary bladder pain syndrome (PBPS) consists of persistent or recurrent pain perceived in the bladder region, worsening with bladder filling and accompanied with lower urinary tract symptoms (LUTS), mainly daytime and nighttime frequency [1]. The aim of our study is to examine a possible effect of injections of Botulinum toxin-A (BoNT/A) in the bladder wall, as an add-on treatment for women with PBPS.

This observational study recruited patients of our department in collaboration with the neuropathic pain office, with an informed consent signed. All women underwent a cystoscopy in order those with Hunner Lesion Disease (HLD) to be identified. 100iu of BoNT/A have been offered for each patient under regional anesthesia. They all have been evaluated with bladder diaries (BDs), pain Visual Analogue Scale (VAS) and International Consultation on Incontinence Questionnaire Overactive Bladder Module (ICIQ-OAB) at the baseline and 2 months after intervention. All women were under treatment for pain symptoms with amitriptyline 50mg/day and intravesical Sodium Hyaluronate for at least 6 months. Patients with a VAS score over 4 and those with ICIQ-OAB score under 4 have been excluded. Statistical analysis has been performed using SPSS v26.

11 women completed the study with a mean age of 51.5yo. Baseline cystoscopy revealed 3 (27.3%) of them with HLD. According to baseline BDs, the mean maximum bladder capacity (mMBC) was 125ml, mean daytime and nighttime frequency were 9.5 and 3.5 respectively. The mean VAS (mVAS) score was 2.5 and the mean ICIQ-OAB score was 6.5, at the beginning of the study. After BoNT/A treatment, mMBC has been increased to 210.5ml, statistically significant to the baseline value (p= 0.025), while mean daytime and nighttime frequency have been decreased to 6.5 and 1.5 respectively, also significantly changed to the beginning (p= 0.03 and p= 0.044 respectively). The mVAS score was 2.6 without almost any change to the baseline. In the subgroup of patients with HLD, the baseline mMBC was 95ml, mean daytime and nighttime frequency were 9.0 and 4 respectively, mVAS score was 3 and the mean ICIQ-OAB score was 7.5. At the reevaluation, mMBC was 135ml, mean daytime and nighttime frequency were 8.5 and 3.5 respectively, mVAS score was 3.5 and the mean ICIQ-OAB score was 7.0, without any significant change for each parameter. None of the patients in any group was needed to be self-cathterized after BoNT/A intervention.

The effect of intradetrusor injections of BoTN/A is already investigated and well proved in cases of neurogenic and idiopathic overactive bladder, although clinical trials are suggesting its use in other lower urinary tract disfunctions too [2][3]. In our study the effect of this intervention had significant statistical and clinical effect in LUTS among women with PBPS. Actually, the already achieved limitation of pain with the primary treatment, might have facilitated voiding, implying a possible placebo effect. The limitations of our study are the short number of subjects enrolled and the short-term follow-up.

Injections of BoTN/A in the bladder wall seem to offer a significant benefit in maximum bladder capacity and urinary frequency for women with PBPS, especially in those without HLD after a short-term follow up.

Chen JL, Kuo HC. Clinical application of intravesical botulinum toxin type A for overactive bladder and interstitial cystitis. Investig Clin Urol. 2020 Feb;61(Suppl 1):S33-S42.
Chiu B, Tai HC, Chung SD, et al. Botulinum Toxin A for Bladder Pain Syndrome/Interstitial Cystitis. Toxins (Basel). 2016 Jul 1;8(7):201.
Mateu Arrom L, Gutierrez Ruiz C, Palou J, et al. Onabotulinumtoxin a injection with or without hydrodistension for treatment of bladder pain syndrome. Int Urogynecol J. 2021 May;32(5):1213-1219.