Axonics therapy uses a small implanted device to send mild electrical pulses to the sacral nerves near the base of your spine, changing the way your brain and bladder (or bowel) communicate. It’s a form of sacral neuromodulation, cleared by the FDA for overactive bladder, urinary urge incontinence, urinary retention, and urgency-frequency symptoms in people who haven’t responded to more conservative treatments like medications or pelvic floor exercises.
How the Nerve Signals Work
The core of Axonics therapy is a thin wire (called a lead) placed near the S3 sacral nerve, which sits in the lower part of your spinal column. A small pulse generator, roughly the size of a large coin, connects to this lead and delivers continuous low-level electrical stimulation. The key insight is that this stimulation doesn’t directly control your bladder or bowel muscles. Instead, it works on the sensory nerve fibers that carry signals between those organs and your brain.
Your bladder and bowel rely on a complex loop of nerve signals to know when they’re full and when it’s appropriate to empty. In conditions like overactive bladder, those signals become hyperactive or poorly timed. Certain nerve fibers (called C fibers) that detect bladder or rectal filling can become overactive due to neurological or inflammatory conditions, triggering the urge to void when the bladder is barely full. Axonics therapy interferes with that abnormal signaling at the spinal cord level, essentially turning down the volume on those misfiring messages before they reach your brain.
For urinary retention, the mechanism works differently. Some people can’t empty their bladder because the pelvic floor muscles and urethra won’t relax properly. Sacral neuromodulation appears to inhibit the “guarding reflex” that keeps those muscles tight, helping them relax so urine can flow. The fact that patients maintain voluntary control throughout therapy confirms that the device modulates the reflex rather than overriding it entirely.
For bowel control, the electrical stimulation targets sensory fibers from the anal sphincter, rectum, and pelvic floor. This reduces the activation of those overactive nerve fibers during rectal filling and blocks abnormal signals from reaching the brain. It also strengthens the internal anal sphincter’s tone through a reflex loop between the somatic nerves and the organs they serve.
The Trial Phase
Before you commit to a permanent implant, you go through a trial period that typically lasts one to two weeks. During this phase, a temporary lead is placed near the sacral nerve, connected to an external battery you wear on your waistband. You track your symptoms in a voiding diary throughout the trial. The standard benchmark is a 50% or greater improvement in symptoms compared to your baseline. If you hit that threshold, you’re considered a candidate for the permanent implant. If you don’t, the lead is simply removed with no lasting effects.
What the Implant Involves
Permanent implantation is a minimally invasive outpatient procedure. The surgeon places the lead near the S3 nerve through a small incision in the lower back, then tunnels a thin wire under the skin to connect it to the pulse generator, which is implanted in the upper buttock area. Most people go home the same day. Recovery is relatively quick, though you’ll have activity restrictions for several weeks while the lead settles into position. Your doctor programs the device to the stimulation settings that worked during your trial, and you can fine-tune certain parameters at home using a handheld remote control.
Battery Life and Device Options
Axonics offers two main system types. The rechargeable version (R15) was approved in 2019 and is designed to last 15 or more years. You charge it through the skin using a small wireless charging pad, typically for about an hour once a month, though this varies with your stimulation settings.
The non-rechargeable version (F15) eliminates the need for any charging. Its battery life depends heavily on the stimulation parameters your body needs. In clinical data, the expected battery life for patients ranged from roughly 5 to 25 years, with an average around 17.5 years. About 75% of patients had projected battery life exceeding 15 years, and 28% exceeded 20 years. When any device’s battery eventually runs out, only the pulse generator needs to be surgically replaced, not the lead.
MRI Compatibility
One practical advantage of the Axonics system is that it’s conditionally safe for MRI scans. Both the rechargeable and non-rechargeable models are approved for 1.5T and 3T MRI using head coils and full-body coils. The R20 model adds clearance for upper and lower extremity coils as well. Before a scan, the MRI technician can use the patient remote control to confirm the device is in MRI-safe mode, without requiring an extra visit to your doctor’s office. Specific guidelines must be followed during the scan to prevent unwanted interactions between the MRI’s magnetic fields and the implant.
How Well It Works Long-Term
Clinical studies show strong durability. In a two-year follow-up of patients with overactive bladder who responded to the initial trial, 90% continued to respond to the therapy based on voiding diary criteria. Among those specifically treated for urinary incontinence, 88% maintained their response at two years, and 28% were completely dry. No serious device-related adverse events were reported in that study. Patients consistently reported high satisfaction with the therapy over time.
These numbers reflect a characteristic of sacral neuromodulation in general: if the trial phase works for you, the permanent implant tends to keep working. The trial phase is specifically designed to screen out non-responders before surgery, which is why long-term success rates are high among those who receive the full implant.