What is SNM?
InterStim therapy is indicated for people with urinary retention, overactive bladder with or without urgency urinary incontinence, and anal incontinence or accidental bowel leakage. The therapy utilizes an innovative and implantable neurostimulator about the size of a stop watch. This device sends mild electrical signals to a nerve located just above the tail bone. This sacral nerve activates or inhibits muscles and smaller nerves that contribute to urinary and bowel control. It also provides signals to the brain about these organs.
How does SNM work?
SNM alters the function of the sacral nerves and the signals they send to the brain regarding bladder and bowel sensations. If the brain and sacral nerves are not communicating effectively, the pelvic organs (bladder and bowel) are not able to function correctly. SNM restores the “normal” communication between the sacral nerves and brain by delivering electrical pulses to the sacral nerves. The electrical stimulation provided by the implantable device helps to modulate signals to the bladder and bowel and may eliminate or reduce bladder and bowel control problems.
When does a woman choose to pursue this treatment?
Many women find that treatments such as drugs, behavior modification, diet changes, pelvic floor exercises or the use of a catheter to empty the bladder do not effectively treat their symptoms. SNM is a great option for women who have not had adequate symptom control with other therapies.
How is SNM performed?
In brief, a small stimulator device is placed underneath the skin near the back of your hip. This is connected to a wire which is located near the sacral nerves and delivers the electrical pulses. Finally, a small hand-held device communicates with the stimulator and allows you to adjust the level of stimulation or turn the device on and off.
Before you undergo SNM, you must complete a baseline bladder and / or bowel diary. This provides you and your urogynecologist with valuable baseline information. Next, SNM therapy is delivered in two procedures. The first is the test stage to see if the therapy will work for you. A test stage is used before implantation of the device to see what the effect of the stimulation is on your symptoms. If this test stage produces positive results for you, the lead will stay in place, and you will proceed to the permanent implant.
- Placing the Test Stimulation Lead (Stage 1): The test-phase (Stage 1 implantation) is initiated in the operating room as an outpatient procedure. An anesthesiologist will administer sedation anesthesia to keep you comfortable during the procedure. While you are lying on your stomach, your urogynecologist will insert a lead and position it near a sacral nerve. During the procedure you may be asked to describe what you feel when the sacral nerve is stimulated. You may feel a "pulling", "tingling" or "tapping" sensation in your pelvic muscles as well as sensation in the vaginal area. Your big toe may also move. You will go home that day. A small wire is attached to the lead. The wire exits through a small incision in your lower back or upper buttock. This wire is connected to the external test phase stimulator that you wear when you go home. Following the procedure, we will instruct you on how to use your hand-held remote to control the external test phase stimulator. Again, you will be given a bladder and / or bowel diary to keep track of your symptoms during the testing phase. This will allow us to determine whether the device is working well for you*.
- Implanting the SNM Device (Stage 2): The implant procedure is performed in an operating room typically one to two weeks following the Stage 1 implantation. As with the test stimulation procedure, the anesthesiology team will make you as comfortable as possible during the procedure. The incision made for the neurostimulator will be about 2 inches long located right above your buttocks. The neurostimulator will be directly attached to the wire that was already placed during the stage 1 procedure. The entire system will be under your skin at that point. It will communicate with a tiny hand-held controller which will allow for you to calibrate your level of stimulation.
*If you do not have a satisfactory response to the therapy during the test phase, your urogynecologist will remove the lead in the operating room.
How long will SNS last?
The lifetime of the battery ranges from five to ten years. You and your urogynecologist will know when the battery life is low (as indicated on the controller), and at that time we will place a new battery. Most times, the wire does not need to be adjusted. Occasionally, women fall or have an accident which might affect the placement of the wire. If this happens, your urogynecologist will evaluate the location of the wire and might have to revise its location.
What are the potential risks associated with SNS?
As with any surgical procedure, problems can occur. These problems may be resolved with reprogramming of the system, medications or surgery. The InterStim System can always be removed if necessary. Although rare, some risks include infection, pain, and lead movement.
Women who have InterStim devices implanted are unable to undergo most MRI studies. If you need to have an MRI, the wire and battery will likely need to be removed.
If at any time your SNM device needs to be removed, this is an easy procedure which is performed in the operating room.
How should I prepare for SNM?
You will need to fill out a bladder or bowel diary before and during the test phase (your urogynecologist will give this to you). It is very important that you fill out this diary honestly and completely as this will serve as your baseline prior to the examination. You will be given specific instructions regarding the preparation for surgery.