Voiding dysfunction, either urinary incontinence or retention, can have a debilitating effect upon the individual’s daily quality of life. Patients with these conditions often face many challenges in their everyday lives and can become preoccupied with constant trips to the bathroom, fear of leaking episodes and sleepless nights. Particularly challenging is the management of patients with detrusor instability (DI) associated with urge incontinence or frequency-urgency syndrome who have failed behavioral modification and pharmocologic therapies. The mainstay of DI therapy, oral anti-cholinergics, can fail for several reasons including poor patient compliance secondary to the poorly-tolerated drug side effects, or due to modest therapeutic efficacy. Equally difficult to manage satisfactorily are patients suffering from non-obstructive urinary retention for whom few therapeutic options exist. Until the introduction of sacral neuromodulation, these patients, managed primarily with intermittent or indwelling catheterization, had little hope of regaining volitional voiding function.
Although the precise pathophysiologic mechanisms underlying these seemingly disparate voiding disorders is not well-understood, the pioneering work of Tanagho1,2 helped to decipher the physiology of bladder, sphincter and pelvic floor function and to explore direct nerve stimulation as a means of modulating aberrant voiding function. In fact, sacral nerve modulation has been proven effective in ameliorating the lower urinary tract symptoms for many patients with voiding dysfunctions. Stimulation of the sacral nerve roots is thought to induce afferent inhibition of sensory processing within the spinal cord and thereby induce an inhibitory effect on the parasympathetic outflow to the detrusor and sphincter.
In 1997, InterStim Therapy, the sacral nerve stimulation device produced by Medtronic, Inc., gained FDA approval as a therapy for individuals with urinary urge incontinence and in 1999, went on to receive FDA approval for frequency-urgency syndrome and non-obstructive urinary retention for patients who fail standard therapies. Currently, more than 600 urologists and urogynecologists worldwide have adopted SNS as a treatment, and more than 8000 devices have been implanted successfully.
InterStim Therapy is a safe, efficacious and reversible therapeutic modality that offers improved voiding function and improved quality of life for appropriately selected individuals. The InterStim electrode delivers a mild electrical signal to the sacral nerve that in turn influences the behavior of the bladder, sphincter and pelvic floor musculature. Placement of the probe is minimally invasive and can be done under local anesthesia, allowing for patient interaction to ensure optimal patient-specific placement. Once the tined probe is positioned in the appropriate sacral foramen via a percutaneous puncture, the tines can be deployed for immediate and secure anchoring into therapeutic position. A neurostimulator is then implanted subcutaneously that can be adjusted by the patient in response to evolving voiding symptoms via a transdermal transducer.
Since its inception, numerous, independent clinical trials have confirmed the efficacy of InterStim Therapy for restoring voiding function in appropriately selected patients. In a series of patients with DI or hyperreflexia, the introduction of InterStim Therapy was associated with a significantly decreased number of pads and voids per day, as well as an increased mean voided volume (p<0.0001).3 Additionally, these patients also reported significant improvement in their quality of life. For patients with demonstrable DI on pre-implantation urodynamics (UDS), the initiation of InterStim sacral nerve neuromodulation resulted in a reduced detrusor activity index on repeat UDS.4 Importantly, the clinical symptoms experience by patients in this series, specifically incontinence episodes, total number of voids and urge events per day, improved in a manner consistent with diminished DI noted on UDS.
Non-obstructive retention has also been successfully treated with sacral nerve stimulation. The return of spontaneous voiding with minimal post-void residual was reported by 77% of women three years following the initial implantation of the InterStim device.2 These findings are consistent with a larger series funded by Medtronic in which 68 patients with urinary retention were implanted with the InterStim system. At 18-month follow-up, 70% had statistically significant improvements in their voided volumes when compared to controls.
The Medtronic device is safe and effective, with a proven track record for individuals appropriately selected. The insertion of the probe and modulator is minimally invasive and well tolerated by most individuals. Importantly this reversible procedure can provide a significant improvement in the quality of life for individuals suffering from a range of urinary dysfunctions.
- Tanagho EA, Schmidt RA., Electrical stimulation in the clinical management of the neurogenic bladder. J Urol. 1988 Dec;140(6):1331-9
- Tanagho EA, Schmidt RA, Orvis BR. Neural stimulation for control of voiding dysfunction: a preliminary report in 22 patients with serious neuropathic voiding disorders. J Urol. 1989 Aug;142(2 Pt 1):340-5
- Hassouna MM et al. Sacral neuromodulation in the treatment of urgency-frequency symptoms: a multicenter study on efficacy and safety. J Urol (2000) 163:1849-54.
- WA Scheepens et al. Eur Urol 43(2003)282-287
- Dasgupta R et al. Long-term results of sacral neuromodulation for women with urinary retention. BJU Int (2004) 94:335-7.
Read More: InterStim Therapy in Voiding Dysfunction