Overview of Sacral Neuromodulation
Sacral neuromodulation is a successful, safe, and minimally invasive treatment that helps manage issues with the lower urinary tract and bowel functions. This includes problems such as urinary and fecal incontinence (involuntary passing of urine or feces), urinary urgency, frequency, and retention (problems with urination), which are common in the United States. This treatment is particularly beneficial for patients who do not see improvements with standard treatments, or with behavioral and drug therapies. In Canada and Europe, sacral neuromodulation is also used for treating chronic constipation.
This therapy was created by Tanagho and Schmidt in 1982 and was approved by the United States Food and Drug Administration (FDA) in 1997. More than 300,000 patients across the globe have been treated with sacral neuromodulation implants. Research shows that between 16% and 29% of the population (with some estimates being as high as 75%) experience an overactive bladder, which includes symptoms of urinary incontinence, urgency, or frequency. Also, about 25% to 40% of those suffering with an overactive bladder do not find satisfactory results even after first and second-line therapies. These patients are often diagnosed with a refractory overactive bladder and could be eligible for sacral neuromodulation therapy.
According to a study by Siegel and his team, which evaluated 340 patients using sacral neuromodulation over 36 months, the success rate for treating overactive bladder was 83% among those who received a sacral neuromodulation implant. Additionally, 80% of these patients reported improvements in all of their urinary symptoms.
While the exact way sacral neuromodulation works is not fully understood, it seems to work by influencing spinal cord reflexes and the brain’s involvement using “afferent signals”, rather than directly stimulating bladder or urethral sphincter muscles (muscles that control the release of urine). The leading theory is that sacral neuromodulation interrupts or interferes with the afferent input to the sacral spinal cord, which controls the bladder’s overactivity, thereby reducing urinary frequency and urgency.
Anatomy and Physiology of Sacral Neuromodulation
The lower urinary tract, which includes your bladder and urethra, has two main jobs: to store and get rid of urine. This is regulated by a complex network of nerves. If these nerves are disrupted, you can develop a neurogenic bladder, which means you can struggle to empty your bladder properly. Symptoms can include difficulty peeing, discomfort after peeing, and problems with bladder storage, like needing to pee frequently, urgently, or not being able to fully empty the bladder.
There are various nerve pathways that help the bladder function properly. The nerves coming from the sacral region of your spinal cord play a key role in letting you pee when you need to. They cause the bladder to contract while at the same time relaxing the muscles that keep you from urinating until you’re ready. Certain medications can help address issues with frequent urination and overactive bladder by influencing these nerve pathways.
On the other hand, there are nerves that work to prevent you from peeing by relaxing your bladder while tightening the muscles controlling urination. Certain medications can also help problems with frequent urination and overactive bladder by increasing the activity of these nerves.
There are also nerves which, when activated, cause the external muscles controlling urine flow to contract. This helps to prevent you from peeing involuntarily. These nerves also send sensory information from areas like the bladder neck and urethra to your brain and spinal cord.
Your body also has a natural reflex to prevent your bladder from leaking when it’s suddenly under pressure, for example when you cough, sneeze, stand up, or laugh.
Your body is also able to recognize when your bladder is getting full through sensory nerves. Activation of these nerves prompts you to pee for proper bladder emptying. These signals also travel to your brain and are processed in specific regions which control when and how you pee.
The rectum, which is connected to your anus, is responsible for storing and passing stool. Passing stool is a mix of voluntary and involuntary muscular actions. Disruptions in the nerves controlling this process can cause symptoms including diarrhea, constipation, and not being able to control when you poop. Birthing-related injuries to the rectum are common causes of such problems.
There are various processes and reflexes that help you pass stool. The process starts when the rectum is sufficiently filled with stool. This sends signals to your brain, telling it that it’s time to poop. This triggers a response which relaxes the muscles of the rectum and anus, allowing for the passage of stool. Once the bulk of the stool has passed, the external muscles of the rectum contract to close off the passage.
The external muscles of the rectum are controlled by specific nerves which help us to delay pooping if necessary. They do so by contracting the muscles and reducing the pressure in the rectum, thus reducing the urge to poop.
There’s also a process known as sacral neuromodulation which can be used to help manage issues with bladder control. However, the exact mechanism of this process is not fully understood.
Why do People Need Sacral Neuromodulation
Sacral neuromodulation is a technique used to treat persistent issues related to the urinary tract, including nonobstructive urinary retention (inability to empty your bladder), urge incontinence (unexpected leakage), and frequent and urgent need to pee. It’s been found to be effective for Parkinson’s patients who have bladder symptoms that resist other treatments. In a recent study, 82% of Parkinson’s patients with bladder troubles saw improvements with this therapy, and many even stopped taking their bladder medication. Moreover, sacral neuromodulation is also used to treat chronic uncontrollable bowel movements.
If you’re considering sacral neuromodulation therapy for urinary incontinence, you should know that it’s usually selected for individuals with severe symptoms that have not improved with other treatments, such as lifestyle changes or medication. These treatments should have been tried for a period of 8 to 12 weeks. During the testing phase of this therapy, it’s recommended that you keep a diary recording your bathroom habits to measure any changes — if there’s a 50% or more reduction in symptoms, the treatment is considered successful.
According to the American Urological Association’s 2021 guidelines, sacral neuromodulation is not recommended for patients with spina bifida or spinal cord injuries because of how variable and progressive these conditions can be. However, it may still be considered for patients with other types of neurogenic bladder (a bladder dysfunction caused by nerve damage) that result in urgency, frequency, or urge incontinence and have not responded well to more conservative treatments.
When a Person Should Avoid Sacral Neuromodulation
Sacral neuromodulation, a technique that sends electrical impulses to the nerves in the lower back, may not be suitable for all patients. Certain conditions can make it unsafe or ineffective, so it’s not recommended for people with a blocked urine flow or an ongoing infection in their lower abdomen. Also, individuals with a severe or quickly worsening nerve disease shouldn’t get this therapy because it might not work well or could lead to complications.
Furthermore, individuals who use certain medical procedures or devices might not be suitable for sacral neuromodulation therapy. These include therapeutic ultrasound and diathermy, which utilize high-frequency sound waves and heat respectively for treatment. Also if you are unable to operate the controller that regulates the implant, this treatment may not be suitable for you. And while earlier models of sacral neuromodulation implants were not compatible with all MRI scans, all new versions made from 2020 onwards are safe for full-body scans. But for implants made before autumn 2019, patients would only be able to have MRI scans of their head and neck.
Consideration also has to be given to age and general health. Though there are no specific restrictions, research has indicated that success rates might be lower in those aged 55 or above, and in those having 3 or more long-term health problems. In these cases, it’s possible that the treatment won’t be as effective in reducing bladder control problems.
Equipment used for Sacral Neuromodulation
For procedures involving sacral neuromodulation (which is a treatment for various bladder and bowel issues), certain equipment is needed. This includes a kit specially designed for this procedure, featuring a ‘tined lead’ (a wire with small wing-like protrusions), a ‘foramen needle’ (a needle intended for puncturing a specific part of the spine), and an ‘internal pulse generator’ (a device that sends electrical pulses to the nerves).
Also necessary are generic surgical supplies like sterile drapes to maintain cleanliness during the procedure and basic tools usually found on a surgical tray. In addition, a device called a ‘C-arm fluoroscopic unit’ is required. This device uses x-rays to provide doctors with a live video feed of the area being operated on, ensuring the lead wire is positioned correctly.
Who is needed to perform Sacral Neuromodulation?
When a medical procedure is being done on the nerves in your body (the first step), there will be a doctor (surgeon), a nurse, and a person who handles the x-ray machine (x-ray technician) present. Then, when the implant is being put in (the second step), the same team of a doctor, nurse and x-ray person are there, but they’re also joined by another person who helps with the surgery (scrub technician). You’ll also have someone there whose job it is to make sure you don’t feel any pain during the surgery. This person could be another type of doctor (an anesthesiologist) or a specially trained nurse (nurse anesthetist).
Additionally, there could also be a person from the company that made the implant gadget that’s going into your body. They’re there to make sure the gadget is ready to be put in, test it, and check the wires (leads) that will help your body move. They make sure everything is working as it should.
How is Sacral Neuromodulation performed
The evaluation phase is like a trial period before actually completing the implant. This trial is done using local anesthesia, and it helps the doctor understand the best place to put the implant. During this procedure, you’ll be lying on your stomach, and a device called a C-arm fluoroscopy will be positioned accordingly. This device helps the doctor identify important landmarks on your sacrum (the triangular bone at the bottom of your spine) including its base, apex, and median sacral crest (the midline area between the sacral holes).
During this procedure, a thin foramen needle is positioned into the S3 foramen, an opening in the sacrum. The success of this implantation can be indicated through different muscle reactions, such as the toe bending upwards or muscle contractions in the pelvic and anal regions. You may experience sensations of fluttering or pulling in the scrotum, vagina, or buttocks. As each individual’s anatomy can be unique, there may be responses related to different sacral nerves (S2 and S4 roots) that may not bring about the best results for therapy.
After the needle is removed, it is replaced with a guide. The needle is then taken out while maintaining the guide in place. A small incision is made at the skin entry point and an introducer is positioned into the S3 foramen. After it’s advanced, the guide is removed, and an introducer sheath is left in place. Following this, a tined lead (a type of electrode) is inserted so that it lies across the sacral foramen. Current recommendations suggest placing the tined lead towards the upper and mid-region of the foramen, which may result in better results.
After all the electrodes have been tested, they should ideally exhibit motor and sensory responses at 2 milliamperes or less. The lead is then passed through a small incision in the buttocks, over the iliac crest (the curved ridge at the top of the pelvic bone), and connected to a percutaneous extension cable. This cable is passed under the skin to the opposite side below the hip, and then connected to an external neurostimulator for the trial period. You’ll undergo a trial period of 7 to 14 days to evaluate the device, after which a decision will be made on whether to proceed with the full implant or remove the device based on the results.
The exact placement of the tined lead during the procedure is very important for the best outcome. Recognizing the landmarks of the sacrum accurately is crucial for success. Recent advancements have introduced the use of methods like computer-assisted lead placement, which can aid in more precise positioning of the electrodes.
Once it’s been confirmed that the trial period was successful with at least a 50% improvement in symptoms, the IPG (implantable pulse generator, the battery part of the device) will be inserted under the skin. Usually, the IPG doesn’t need to be stitched into the pocket to avoid a sensation of pulling or uneasiness because it rarely dislodges. In some cases, an antimicrobial mesh pouch might be used to secure the device and prevent infection.
Any necessary adjustments to the device can be made during follow-up visits and you’ll typically have yearly visits to check the device and manage symptoms. The longevity of the device depends on its battery life, which is typically around 5 years for non-rechargeable implants. New technologies have introduced rechargeable devices with battery lives of up to 15 years. Technological advancements and customization have greatly enhanced the effectiveness and convenience of these procedures.
Possible Complications of Sacral Neuromodulation
Sacral neuromodulation, a treatment commonly used for bladder and bowel control issues, might sometimes face complications. Some of the most serious problems related to the treatment are lead migration (when the wire that carries electrical signals moves out of place), discomfort at the implant site, and infection. These complications can affect the treatment’s efficiency and might sometimes need more medical procedures or the device to be removed.
One common issue is when the patient doesn’t seem to benefit from the therapy anymore. In this case, the healthcare provider needs to make sure that the neurostimulator (the device providing treatment) is switched on and working properly. They would also need to check the resistance of the electrodes (small devices that deliver electrical impulses to the nerves) to make sure there’s no open or short circuit (a term to describe when an electrical component isn’t working properly). If all looks well, they might adjust the device’s program, tweaking the frequency, intensity, and duration of the electrical impulses delivered to try and provide better relief from the symptoms.
In some cases, the wire carrying the electrical signals (also known as the ‘lead’) might move out of place or may not have been placed correctly in the first place. This can usually be detected using an x-ray. If this happens, surgery to shift the lead back into place should only be considered as the last option. It’s important first to check with the manufacturer of the device to troubleshoot and explore other possible solutions.
If standard sacral neuromodulation therapy does not provide improvement despite initial success, there’s another method that could be used. It’s called bilateral sacral electrical pudendal nerve stimulation, an advanced method that targets a specific nerve to help manage the symptoms.
What Else Should I Know About Sacral Neuromodulation?
Overactive bladder, which causes a frequent and sudden urge to urinate, can be a challenging problem. Researchers studied the combined use of two treatments: a nerve-stimulating technique called sacral neuromodulation and a medication called tolterodine. After three months, this combined treatment was found to be more effective compared to the medication alone. It helped improve several bladder-related symptoms, including the amount of urine voided at once, and the body’s ability to hold urine before feeling an urgent, uncontrollable urge to urinate.
There’s another treatment called percutaneous tibial nerve stimulation (PTNS) that can also help with overactive bladder. PTNS involves gently stimulating a nerve in your foot (the tibial nerve) with a needle connected to an energy source. This stimulation helps control the nerves responsible for bladder function. While you might feel a “tingling” or “pulsing” sensation in your foot or ankle, the procedure is usually not painful. Sessions last for 30 minutes, take place every week, and although some people might notice an improvement early on, many need several sessions before seeing substantial benefits. PTNS has been found to successfully improve symptoms in 60% to 80% of patients, and it continues to be beneficial even when the nerve isn’t being actively stimulated.
However, PTNS has a few drawbacks, like the need for regular clinic visits and a commitment to a 12-week treatment trial. Additionally, while PTNS is generally safe and less invasive than other treatments, it hasn’t been tested as long-term as sacral neuromodulation. Therefore, choosing between these two treatments is largely dependent on what equipment is available, how close the clinic is, and what kind of procedure the patient is comfortable with.
Other treatment options for overactive bladder include botulinum toxin injections and a wearable device that stimulates the tibial nerve. Botulinum toxin injections are effective but can cause side effects like urinary tract infections and urinary retention. The wearable device, on the other hand, has been found to be effective and easy to comply with and is approved by the Food and Drug Administration (FDA).
Sacral neuromodulation can also be used to manage chronic pelvic pain, which sometimes occurs with conditions like interstitial cystitis. While it’s not yet cleared by the FDA for this use, some studies suggest that it can significantly reduce pain levels.
In short, sacral neuromodulation can be a safe, effective, and reversible alternative treatment for stubborn cases of overactive bladder, issues with urine retention, and fecal incontinence.
