Guide to Sacral Neuromodulation for Overactive Bladder

Neuromodulation for Overactive Bladder is a therapy in which small electrical signals stimulate the nerves associated with urine storage. These signals change the way that the bladder sends messages to the brain. In OAB, it is those signals which are “overactive” and neuromodulation can help to decrease them. Percutaneous Tibial Neuromodulation (also called Peripheral Tibial Nerve Stimulation) is one way of stimulating those nerves. However, right now patients have to come into the office for every PTNM treatment. This is difficult for many patients. Sacral neuromodulation also stimulates the bladder nerves to decrease feelings of bladder urgency, but can be implanted so that a patient is treated continuously without such frequent visits.

Sacral neuromodulation (SNM) stimulates the nerve that controls the bladder by placing a tiny wire through a small, natural, opening in the sacrum. The sacrum is a the large, shield-shaped bone in your pelvis (it makes up the “backbone” of your pelvis). The wire is placed in this location for several reasons. The sacrum provides safe access to the bladder nerves because the nerve is relatively close to the skin in this location and there are no body structures between the skin and the nerve that could be injured by the wire. The sacrum also provides a stable attachment point so that the lead is held firmly in place. Finally, the sacrum is close to the buttocks which allows the neuromodulation battery to be buried deep in the fat.

Sacral neuromodulation is tested by first placing the wire under the skin and stimulating with a battery worn over the skin for 1-2 weeks. Only people who have at least 50% improvement and are satisfied with the treatment have the permanent battery placed in the operating room. Once the battery is in place, stimulation is continuous. Patients have a “remote control” that allows them to control the therapy if needed. However, most patients do not have to make any routine changes to their stimulation. The implanted battery lasts many years and can be changed under a local anesthetic in the operating room.

For many Overactive Bladder (OAB) therapies, success is often defined as at least 50% improvement in symptoms. That means that someone who is urinating on average 20 times a day would need to decrease to at least 10 times per day. If you are leaking about 4 times per day, you would need to decrease to 2 episodes or less per day. Many people see considerably more improvement than this but we generally do not consider the therapy successful if you the patient sees less than that 50% improvement. However, there is no way to reliably predict who will see that kind of response. For that reason sacral neuromodulation therapy is always tested before being permanently implanted, to see who will respond and who will not.

Staged Testing of Sacral Neuromodulation

A sacral neuromodulator consists of two separate parts, the lead (wire) which actually delivers the stimulation to the nerve and the patient generator which generates the signal and contains the battery. The generator is never placed until a patient shows the required improvement during a test. The generator is an expensive component and is designed to last for years and a test only has to last a week or two. It is not appropriate to place a patient generator unless a proper test has demonstrated at least 50% improvement in symptoms. There are two different ways of testing sacral neuromodulation prior to implanting the device permanently. The first method is often called staged testing or sometimes advanced testing. In staged testing, the permanent lead is placed under the skin next to the nerve but the generator is not placed at that time. Instead, the lead is connected to a very thin wire that exits the skin and is attached to a small temporary battery that you wear in an elastic belt around your waist. This allows you to test the therapy for multiple weeks without having the patient generator implanted. The lead is usually placed while you are under anesthesia, either heavy sedation or general anesthesia (I prefer to place these under general anesthesia in my patients). Once you wake up, the tiny wire exiting your skin is attached to the small temporary battery and the stimulation is set. We adjust the type of stimulation and how high it is set before you leave the hospital that day. Patients who do not see improvement early in the test can adjust the stimulation (you have a remote control) to see if we can improve the results. Over the next couple of weeks, you are able to check whether you see enough improvement and whether you like the stimulation. If you see at least a 50% response in your symptoms and you are pleased with the stimulation, the next step is to place the generator. The generator is placed in the operating room, though you do not have to undergo general anesthesia after a staged test to place the generator. The generator is placed in the same location that the lead was connected to the small wire so a new incision isn’t necessary. I typically have patients receive light sedation and use a local anesthetic to be sure the area is very numb. If you have not seen satisfactory improvement, all of the parts of the neuromodulator are complete removed after the test.

Peripheral Testing of Sacral Neuromodulation

There is another way to test the success of sacral neuromodulation before implanting permanently that is called a basic evaluation or peripheral nerve evaluation. Unlike a staged evaluation, a peripheral evaluation implants a temporary wire not a permanent lead. Basic evaluations do not have to occur in the operating room and most patients do not need any type of sedation Instead, all that is required is that the area is numbed with a local anesthetic. Since the permanent lead is not placed, there are no incisions. The wire is simply threaded through a needle that is placed under the skin. Also, percutaneous evaluations are typically placed on both sides to test both the right and left nerves. The testing period is usually shorter than with staged testing because, unlike the lead, the wire used is not anchored to anything. The wires are also attached to a small battery worn in a belt around the waist during testing. Patients still have to show at least a 50% improvement in symptoms. If satisfactory improvement is seen during this test, the step is performed in the operating room, just as with a staged test. However, after a successful percutaneous test, both the lead and the generator can be implanted at once. Those who do not have a successful percutaneous test should undergo a staged test as a next step. A significant number of people who do not see improvement with the basic test will see respond to an advanced test.

How Successful is Sacral Neuromodulation

One way of looking at the success of SNM is how many patients have a successful test (>50% improvement) and have the device permanently implanted. Approximately 70-85% of patients see this much improvement. However, it is important to remember that OAB is a chronic disease and you likely want to know how well the treatment performs over time. Like all OAB therapies, it appears there is some drop in success rates over time. One study demonstrated a decline to 62% success rate at 5 years. Still, for a majority of patients, SNM remains a successful and satisfying therapy for many years. In studies comparing older and younger patients, there does not appear to be any significant difference in how well older patients respond to therapy.

The most significant risk associated with sacral neuromodulation (SNM) is infection of the device. An infected sacral neuromodulation device must be removed entirely. A new device can be place after a suitable time to clear the infection and heal but this is a very expensive and distressing complication. Historically, rates of removal for infection have ranged from 3-10% but more recent evidence suggests infection rates can be around 1% or even lower. Several studies have looked at increased rates of infection in certain types of patients, such as those with diabetes, in an effort to decrease infections. In my own practice, over the last few years, I developed an infection prevention program which appears to reduce the rate of device infections by nearly 90%. Infections, however, have not been entirely eliminated even with this protocol.

Patients may have discomfort at the site of the device that is not associated with infection. Some patients are able to have the device relocated, though some elect to have the entire device removed. In total, as many as 30% of patients may have their device either replaced or entirely removed due to various reasons. Patients with older devices may not be able to have many types of MRI studies. There is a concern that the device could be moved or could heat up in the magnetic field of an MRI. If patients with these older devices need an MRI study, the SNM device must remove the entire device. SNM devices placed today do not have this limitation and a device removed to allow an MRI can be replaced by a newer neuromodulator that is compatible with MRI. If you have an older device and are unsure of its MRI compatibility, contact the surgeon who placed the device and they can tell you whether it is MRI compatible based on when it was implanted.

SNM is frequently used as a treatment for Overactive Bladder including frequent or urgent urination, with or without urine leakage. But another common use for SNM is in the treatment of fecal incontinence associated with fecal urgency. In patients who have moderate to severe symptoms of both urinary urgency and fecal urgency, sacral neuromodulation may be able to provide improvement for both of these symptoms. Much as with treatment for OAB and urinary incontinence, early therapies for Fecal Incontinence (FI) often center around more conservative therapies. These are therapies with few risks or side effects. Dietary changes that help to manage either constipation or diarrhea are often recommended. Pelvic floor exercises, often guided by a pelvic floor physical therapist, can be useful as well. However, just as with urinary incontinence, some patients unfortunately do not respond to these therapies. In some of these patients, sacral neuromodulation may be an appropriate therapy.

When treating Fecal Incontinence, placement of the sacral neuromodulator is identical. Thus, patients with both bladder issues such as OAB and urgency incontinence as well as problems with Fecal Incontinence, can potentially have both treated with one therapy. Sacral Neuromodulation is quite effective for treatment of FI and implantation rates are similar or higher than those for bladder symptoms. While long-term success rates do decrease somewhat over time, most patients remain satisfied with therapy for FI for years. In one study, at 5 years, 74% of patients remained satisfied with their improvement in both problems.

For patients with both urinary symptoms associated with OAB as well as Fecal Incontinence, sacral neuromodulation may offer a unique opportunity to treat both problems with one therapy. Given the frequency with which these two disorders coexist, this is a common consideration.

There are several possible advantages in seeing a bladder health specialist for the evaluation and management of refractory overactive bladder. Bladder symptoms that are refractory to multiple treatments including medications and behavioral therapies may be more likely to come from a bladder problem that is not OAB. A specialist in bladder health may be more experienced in evaluating these kinds of problems and can perform a more comprehensive search for possible alternative causes.

In addition, when considering advanced therapies for refractory OAB, it can be useful to have options of all of the advanced therapies. A bladder health specialist has the expertise to offer all of the advanced therapies for OAB and the experience to deliver them most effectively.