[Use and mechanism of botulinum toxin in overactive bladder treatment]

Overactive bladder is very frequent in central neurogenic patients; it is a major cause of refractory incontinence despite anticholinergic treatment. In non-neurogenic patients it results in very distressing symptoms that associate urgency with or without incontinence and frequency. Botulinum toxin A is a well known agent used previously in the treatment of striated muscle spasmodism, which blocks the release of acetylcholine from nerve endings and neuro-muscular transmission. Its recent use in urology revealed a dramatic improvement in clinical and urodynamic parameters of the overactive bladder, associated with a long lasting effect over 6 to 9 months and an excellent tolerance. In neurogenic patients, the efficacy of botulinum injection was demonstrated over a placebo control group. Toxin was injected at 20 to 30 different sites in the detrusor muscle, with cystoscopy guidance. Recent studies showed a sub-epithelial mechanism of action on neuropeptides, which could explain an inhibitory effect of both efferent and afferent arms of the micturition reflex. Further studies remain necessary regarding the respective doses of Dysport and Botox toxin, selection of patients, combination with anticholinergic treatment, effects of repeated injections.