In the last years, botulinum toxin type A (onab/A) has been increasingly used as a treatment option for overactive bladder symptoms in patients affected by either neurogenic and idiopathic detrusor overactivity (DO). How onab/A injected into the detrusor muscle improves overactive bladder symptoms in neurologic patients has been only partially investigated.Some evidence suggested that the neurotoxin probably reduces detrusor muscle contraction blocking detrusor muscle cholinergic innervation. However, recent experimental observations indicated that onab/A determines more complex effects on bladder activity acting on afferent innervations as well as on the efferent one. Only few experimental studies have investigated the activity of onab/A on bladder afferent nervous transmission. Experimental studies in animals showed that Nerve Growth Factor (NGF) elicits increased sensation, urgency and DO. Although there are some evidence on the ability of onab/A to improve DO and to reduce bladder and urinary content of NGF, how onab/A influences NGF expression and the expression of TrKa, p75 and TRPV1 receptors is still unclear. The hypothesis is that onab/A reduces NGF bladder tissue levels and in the same time it modulates the gene expression of NGF associated receptors (TrkA, p75 and TRPV1).

NGF has been suggested to modulate neurotransmitters' release, induces synaptic reorganization and influences neuronal excitability acting on Trk/A and p75 associated receptors. Moreover, recent observations indicated that NGF-induced DO and noxious input depend on the interaction of NGF with TRPV1, that is over-expressed in overactive bladders and interstitial cystitis/painful bladder syndrome. From a clinical point of view, a decrease in urinary NGF levels has been detected in patients with DO treated with onab/A. Although there are some evidence on the ability of onab/A to improve DO and to reduce bladder and urinary content of NGF, how onab/A influences NGF expression and the expression of TrKa, p75 and TRPV1 receptors is still unclear.

Inclusion Criteria:

Patients affected by refractory overactive bladder (OAB) symptoms and detrusor overactivity (idiopathic and neurogenic DO) refractory to conventional anticholinergics (at least 3 antimuscarinic agents -- tolterodine, oxybutynin and solifenacin -- each taken for at least 1 month).

Exclusion Criteria:

• OAB symptoms due to bladder outlet obstruction because of urogenital prolapse in females and benign prostatic hyperplasia in males,
• recurrent urinary tract infections,
• cognitive impairment,
• pregnancy,
• anticoagulant therapy,
• psychoactive agents modulating bladder function (venlafaxine, amitriptyline), aminoglycosides, and other drugs thought to interfere with bladder function

We consecutively enrolled 18 patients with neurogenic DO (8 patients with spinal cord injury: 7 men and 1 women, mean age: 46±2 yrs, disease duration 6.25±1 yrs; 10 patients with suprapontine bilateral lesions: 4 men and 6 women, mean age: 55±4 yrs, disease duration 6.6±1.49 yrs ) and 7 with idiopathic DO (3 men and 4 female, mean age: 53±5 yrs, disease duration 7.1±1.53 yrs). All the patients had overactive bladder (OAB) symptoms and DO refractory to conventional anticholinergics (at least 3 antimuscarinic agents -- tolterodine, oxybutynin and solifenacin -- each taken for at least 1 month). Anticholinergics were discontinued one month before entry into the study.