Sacral (S3) segmental nerve stimulation as a treatment for urge incontinence in patients with detrusor instability: Results of chronic electrical stimulation using an implantable neural prosthesis

textabstractMost patients with urge incontinence and idiopathic detrusor instability are initially treated conservatively with bladder retraining, pelvic floor exercises and biofeedback, while in the majority this regimen will be supplemented with anticholinergic drugs. The urinary incontinence guideline panel has summarized the literature on results achieved with various drugs for urge incontinence, and found that oxybutynin and terodiline appeared to be the most effective.[1] Subjective cure rates of up to 44 percent over placebo and decreased urinary incontinence rates in up to 56 percent over placebo were achieved with these drugs.[1] Interestingly, no changes in urodynamic parameters were found in well designed drug trials despite symptomatic improvement.2 and 3 Fortunately, many patients seem to be satisfied with a less than optimal result. Patients who do not achieve an acceptable condition remain a therapeutic problem and alternative procedures, with variable success rates, such as bladder transection, transvesical phenol injection of the pelvic plexus, augmentation ileocystoplasty and even urinary diversion, are being advocated.[4] Unilateral sacral segmental nerve stimulation by a permanent foramen S3 electrode (neuromodulation) offers a nondestructive alternative for those whose condition is refractory to conservative measures. The aim of this treatment modality is to achieve detrusor inhibition by chronic electrical stimulation of afferent somatic sacral nerve fibers via an implanted electrode coupled to a subcutaneously placed pulse generator. The ratio of this treatment modality is based on the existence of spinal inhibitory systems that are capable of interrupting a detrusor contraction. Inhibition can be achieved by electrical stimulation of afferent anorectal branches of the pelvic nerve, afferent sensory fibers in the pudendal nerve and muscle afferents from the limbs.5, 6 and 7 Most of these branches and fibers reach the spinal cord via the dorsal roots of the sacral nerves. Of the sacral nerve roots the S3 root is the most practical for use in chronic electrical stimulation.[8] We evaluate the effectiveness of this treatment modality in patients with urge incontinence due to bladder instability