Mechanism and Priority of Botulinum Neurotoxin A versus Sacral Neuromodulation for Refractory Overactive Bladder: A Review

<b><i>Background:</i></b> The treatment of common overactive bladder (OAB) has reached a consensus, but there is not a clear answer to the treatment of refractory OAB (ROAB). ROAB is defined as nonresponsive to treatment with behavioural and oral therapies. The disease can influence the physical and mental health of patients, cause poor quality of life, and create an urgent socio-economic burden. With the advancement of medical treatment, the treatment of OAB has improved significantly in the last 2 decades, especially ROAB, by the usage of botulinum neurotoxin A (BoNT-A) and sacral neuromodulation (SNM). Many studies have demonstrated their effectiveness and safety. However, which therapy is the optimal method remains unclear for patients with ROAB, and the exact mechanism involved in the procedures is still unknown. <b><i>Summary:</i></b> This review is to clarify the mechanisms, advantages, and disadvantages of SNM and BoNT-A in treatment of ROAB, and determine whether there is an order effect of SNM and BoNT-A in managing ROAB. <b><i>Key Messages:</i></b> BoNT-A and SNM mainly act on the peripheral nervous system and central nervous system, respectively. But BoNT-A and SNM may partly act on the central and peripheral nervous systems, separately. SNM may be a better choice than BoNT-A in the long time. At the same time, BoNT-A and SNM can treat the ROAB as the first and next steps, and the sequence of both would not affect the effectiveness of each other.