Clinical and neurophysiologic study of botulinum A toxin effect on neurogenic and idiopathic detrusor overactivity.

INTRODUCTION AND OBJECTIVES: Recent observations indicate that Botulinum A toxin (BoNT/A) produces complex effects on the bladder activity acting also on afferent pathways. In humans, in a study investigating the effects of bladder filling on the H-reflex size, bladder filling suppressed the H-reflex whereas in patients with spinal cord injury (SCI) it did not. Testing H- reflex size during bladder filling on urodynamic studies therefore allows the investigation of bladder afferents on spinal excitability. We investigated in patients with neurogenic and idiopathic detrusor overactivity (IDO) the clinical effect and the mechanism of action of BoNT/A injected into the detrusor muscle. METHODS: 16 patients with neurogenic detrusor overactivity (8 with Parkinson’s disease-PD and 8 with spinal cord injury-SCI) and 8 patients with IDO participated in the study. All the patients underwent urodynamics and the H- reflex study from soleous muscle before and 4 weeks after intradestrusor BoNT/A injection. RESULTS: At baseline, (pre-BoNT/A) in PD patients and in those with IDO, the H- reflex from soleous muscle was significantly inhibited at maximal bladder capacity (MCC), whereas it remained unchanged in patients with SCI. Four weeks after BoNT/A injection, in patients with PD and in those with IDO the H- reflex was not inhibited at MCC. Conversely in patients with SCI the H reflex decreased at MCC, even though not significantly (Table 1 and 2). CONCLUSIONS: The lack of H- reflex inhibition at MCC in patients with PD and IDO suggests that, besides the known effect on efferent pathways, BoNT/A treatment improves bladder function by acting also on afferent fibers. The changes in the H- reflex at MCC after BoNT/A in patients with SCI suggest that BoNT/A likely modulates C-fibers neurotransmission.