Sacral Nerve Stimulation
Sacral nerve stimulation, also known as sacral neuromodulation, is a procedure in which the sacral nerve at the base of the spine is stimulated by a mild electrical current from an implanted device. It is done to improve functioning of the urinary tract, to relieve pain related to urination, and to control fecal incontinence.
As a proven treatment for urinary incontinence, sacral nerve stimulation (SNS) has recently been found effective in the treatment of interstitial cystitis, a disorder that involves hyperreflexia of the urinary sphincter. SNS is also used to treat pelvic or urinary pain as well as fecal incontinence.
A person's ability to hold urine or feces depends on three body functions:
- a reservoir function represented by the urethra/bladder or colon
- a gatekeeping function represented by the urethral or anal sphincter
- the brain's ability to control urination, defecation, and nerve sensitivity
A dysfunction or deficiency in any of these components can result in incontinence. The most common forms of incontinence are stress urinary incontinence and urge incontinence. Stress incontinence is related to an unstable detrusor muscle that controls the urinary sphincter. When the detrusor muscle is weak, urine can leak out of the bladder from pressure on the abdomen caused by sneezing, coughing, and other movements. Urge incontinence is characterized by a sudden strong need to urinate and inability to hold urine until an appropriate time; it is also associated with hyperactivity of the urinary sphincter. Both conditions can be treated by SNS. SNS requires an implanted device that sends continuous stimulation to the sacral nerve that controls the urinary sphincter. This treatment has been used with over 1500 patients with a high rate of success. It was approved in Europe in 1994. The Food and Drug Administration (FDA) approved SNS for disturbances that are usually treated by augmentation of the sphincter muscle or implanting an artificial sphincter can benefit from electrical stimulation of the sacral nerve. Although the mechanism of SNS is not completely clear, researchers believe that the patient's control of the pelvic region is restored by the stimulation or activation of afferent fibers in the muscles of the pelvic floor.
Urinary incontinence affects between 15% and 30% of American adults living in the community, and as many as 50% of people confined to nursing homes. It is a disorder that affects women far more frequently than men; 85% of people suffering from urinary incontinence are women. According to the chief of geriatrics at a Boston hospital, 25 million Americans suffer each year from occasional episodes of urinary or fecal incontinence.
Interstitial cystitis is less common than urinary or fecal incontinence but still affects 700,000 Americans each year. The average age of IC patients is 40; 25% of patients are younger than 30. Although 90% of patients diagnosed with IC are women, it is thought that the disorder may be underdiagnosed in men.
Sacral nerve stimulation (SNS) is conducted through an implanted device that includes a thin insulated wire called a lead and a neurostimulator much like a cardiac pacemaker. The device is inserted in a pocket in the patient's lower abdomen. SNS is first tried on an outpatient basis in the doctor's office with the implantation of a test lead. If the trial treatment is successful, the patient is scheduled for inpatient surgery.
Permanent surgical implantation is done under general anesthesia and requires a one-night stay in the hospital. After the patient has been anesthetized, the surgeon implants the neurostimulator, which is about the size of a pocket stopwatch, under the skin of the patient's abdomen. Thin wires, or leads, running from the stimulator carry electrical pulses from the stimulator to the sacral nerves located in the lower back. After the stimulator and leads have been implanted, the surgeon closes the incision in the abdomen.
Incontinence significantly affects a patient's quality of life; thus patients usually consult a doctor when their urinary problems begin to cause difficulties in the workplace or on social occasions. A family care practitioner will usually refer the patient to a urologist for diagnosis of the cause(s) of the incontinence. Patients with urinary and fecal incontinence are evaluated carefully through the taking of a complete patient history and a physical examination. The doctor will use special techniques to assess the capacity of the bladder or rectum as well as the functioning of the urethral or anal sphincter in order to determine the cause or location of the incontinence. Cystoscopy, which is the examination of the full bladder with a scope attached to a small tube, allows the physician to rule out certain disorders as well as plan the most effective treatment. These extensive tests are especially important in diagnosing interstitial cystitis because all other causes of urinary urgency, frequency, and pain must be ruled out before surgery can be suggested. Cystoscopy is done under anesthesia and often works as a treatment for IC. Once the doctor has made the diagnosis of urinary incontinence due to sphincter insufficiency, he or she will explain and discuss the surgical implant with the patient. SNS may be tried out on a temporary basis. The same pattern of diagnosis and treatment is used for patients with IC and fecal incontinence. Temporary implants can help eliminate those patients who will not benefit from a permanent implant.
Following surgery, the patient remains overnight in the hospital. Antibiotics may be given to reduce the risk of infection and pain medications to relieve discomfort. The patient will be given instructions on incision care and follow-up appointments before he or she leaves the hospital.
Aftercare includes fine-tuning of the SNS stimulator. The doctor can adjust the strength of the electrical impulses in his or her office with a handheld programmer. The stimulator runs for about five to 10 years and can be replaced during an outpatient procedure. About a third of patients require a second operation to adjust or replace various elements of the stimulator device.
In addition to the risks of bleeding and infection that are common to surgical procedures, implanting an SNS device carries the risks of pain at the insertion site, discomfort when urinating, mild electrical shocks, and displacement or dislocation of the leads.
Patients report improvement in the number of urinations, the volume of urine produced, lessened urgency, and higher overall quality of life after treatment with SNS. Twenty-two patients undergoing a three to seven-day test of sacral nerve stimulation on an outpatient basis reported significant reduction in urgency and frequency, according to the American Urological Association. Studies have indicated complete success in about 50% of patients. Sacral nerve stimulation is being used to treat fecal incontinence in the United States and Europe, with promising early reports. As of 2003, SNS is the least invasive of the recognized surgical treatments for fecal incontinence.
Morbidity and mortality rates
Sacral nerve stimulation has been shown to be a safe and effective procedure for the treatment of both urinary and fecal incontinence. Two groups of researchers, in
There are three types of nonsurgical treatments that benefit some patients with IC:
- Behavioral approaches. These include biofeedback, diet modifications, bladder retraining, and pelvic muscle exercises.
- Medications. These include antispasmodic drugs, tricyclic antidepressants, and pentosan polysulfate sodium, which is sold under the trade name Elmiron. Elmiron appears to work by protecting the lining of the bladder from bacteria and other irritating substances in urine.
- Intravesical medications. These are medications that affect the muscular tissues of the bladder. Oxybutynin is a drug that is prescribed for patients who are incontinent because their bladders fail to store urine properly. Capsaicin and resiniferatoxin are used to treat hyperreflexia of the detrusor muscle.
Surgical alternatives to SNS are considered treatments of last resort for IC because they are invasive, irreversible, and benefit only 30–40% of patients. In addition, some studies indicate that these surgeries can lead to long-term kidney damage. They include the following procedures:
- Augmentation cystoplasty. In this procedure, the surgeon removes the patient's bladder and replaces it with a section of the bowel—in effect creating a new bladder. The patient passes urine through the urethra in the normal fashion.
- Urinary diversion. The surgeon creates a tube from a section of the patient's bowel and places the ureters (tubes that carry urine from the kidneys to the bladder) in this tube. The tube is then attached to a stoma, or opening in the abdomen. Urine is carried into an external collection bag that the patient must empty several times daily.
- Internal pouch. The surgeon creates a new bladder from a section of the bowel and attaches it inside the abdomen. The patient empties the pouch by self-catheterization four to six times daily.
Walsh, Patrick C., MD, et al., eds. Campbell's Urology, 8th ed. Philadelphia: W. B. Saunders Company, 2002.
Elliott, Daniel S., MD. "Medical Management of Overactive Bladder." Mayo Clinic Proceedings 76 (April 2001): 353-355.
Ganio, E., A. Masin, C. Ratto, et al. "Short-Term Sacral Nerve Stimulation for Functional Anorectal and Urinary Disturbances: Results in 40 Patients: Evaluation of a New OPtion for Anorectal Functional Disorders." Disorders of the Colon and Rectum 44 (September 2001): 1261-1267.
Kenefick, N. J., C. J. Vaisey, R. C. Cohen, et al. "Medium-Term Results of Permanent Sacral Nerve Stimulation for Faecal Incontinence." British Journal of Surgery 89 (July 2002); 896-601.
Linares Quevedo, A. I., M. A. Jiminez Cidre, E. Fernandez Fernandez, et al. "Posterior Sacral Root Neuromodulation in the Treatment of Chronic Urinary Dysfunction. [in Spanish] Actas urologicas espanolas 26 (April 2002): 250-260.
American Urological Association (AUA). 1120 North Charles Street, Baltimore, MD 21201. (410) 727-1100. <www.auanet.org>.
National Association for Continence (NAFC). P. O. Box 1019, Charleston, SC 29402-1019. (843) 377-0900. <www.nafc.org>.
National Kidney Foundation. 30 East 33rd Street, Suite 1100, New York, NY 10016. (800) 622-9010 or (212) 889-2210. <www.kidney.org>.
National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC). 3 Information Way, Bethesda, MD 20892-3580.
Interstitial Cystitis Association. Sacral Nerve Stimulation Can Relieve Interstitial Cystitis, Studies Suggest. <www.ichelp.com/research/SacralNerveStimulationCanRelieveIC.html>.
Mayo Clinic. Sacral Nerve Stimulation. <www.mayoclinic.org/incontinence-jax/sacralstim.html.>
Nancy McKenzie, PhD
WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?
SNS devices are implanted under general anesthesia by urologists, who are physicians specializing in treating disorders of the urinary tract. The procedure is usually performed in a hospital.
QUESTIONS TO ASK THE DOCTOR
- Am I likely to benefit from SNS?
- How many stimulators have you implanted?
- How many of your patients consider SNS a successful treatment?
- What side effects have your patients reported?