Sacral neuromodulation as a functional treatment of bladder overactivity.

Sacral neuromodulation, namely the electrical stimulation of the sacral nerves has become an alternative treatment for cases of idiopathic bladder overactivity. The mechanism of action in this type of spinal cord modulation is only partially understood but it seems to involve stimulation of inhibitory interneurons. Temporary sacral nerve stimulation is the first step. It consists of the temporary application of neurostimulation as a diagnostic test in order to check the integrity of the sacral root and determine the best location for the implant. If the test stimulation is successful, a permanent device is implanted. In experienced hands, this is a safe procedure. When the patients are selected on the basis of sound criteria, more than three-quarters of them show a clinically significant improvement with a reduction in the frequency of incontinence episodes by more than 50%; however, the results vary according to each author's method of evaluation. The application of this technique should be combined with careful follow-up and attentive adjustments of the stimulation parameters in order to optimize the coordination of activity between the neurological systems involved.