Botulinum toxin is a presynaptic
neuromuscular blocking agent inducing selective and reversible
muscle weakness up to several months when injected intramuscularly in minute quantities. Different medical disciplines have discovered the toxin to treat mainly muscular hypercontraction. In urology, indications for
botulinum-A toxin have been neurogenic detrusor overactivity, detrusor-sphincter
dyssynergia, motor and sensory urge and, more recently, chronic prostatic
pain. The available literature was reviewed using Medline Services. The keywords "
botulinum-A toxin", "detrusor-sphincter
dyssynergia", "
neurogenic bladder", "
spinal cord injury", "
denervation", "chronic prostatic
pain", "chronic urinary retention" were used to obtain references. A toxin injection is effective to treat detrusor-sphincter
dyssynergia when injected either transurethrally or transperineally.
After treatment, external urethral sphincter pressure, voiding pressure and post-void residual volume decreased. The effect lasts between 2 to 9 months depending on the number of
injections. Best indications seem to be
multiple sclerosis and incomplete
spinal cord injury patients suffering from neurogenic detrusor overactivity and detrusor-sphincter
dyssynergia. According to the previous results, the use of
botulinum-A toxin injections into the external urethral sphincter has been extended to a variety of bladder obstructions and to decrease outlet resistance in patients with acontractile detrusor. In cases of successful treatment, spontaneous voiding re-occurs and catheterization can be resumed.
Injections of the toxin into the external urethral sphincter also seem to have a beneficial effect on chronic prostatic
pain, presumably by reducing hypertonicity and hyperactivity of the external urethral sphincter.
Injections of
botulinum-A toxin into the detrusor muscle has first been tested to treat neurogenic detrusor activity in spinal cord injured patients and in
myelomeningocele children. Long lasting (mean 9 months) detrusor relaxation occurs after injection of usually 300 units of
Botox). Continence is restored in about 95% of the patients and
anticholinergic drugs can be markedly reduced or even stopped. Excellent results of
botulinum-A toxin injections into the detrusor in neurogenic detrusor overactivity have lead to an expansion of this treatment to incontinence due to idiopathic detrusor overactivity. Although preliminary results are promising, adequate dosage of the toxin required for this indication is not yet known. In conclusion, it appears that
botulinum toxin injection into either the external urethral sphincter or the detrusor offers new promising treatment options for many different urological dysfunctions. However, large controlled trials are absolutely required to establish the role of
botulinum-A toxin injections in the fields of urology and neurourology on evidence based medicine.