Over the last 25 years, sacral neuromodulation (SNM) has proven to be a reliable treatment for refractory overactive bladder, fecal incontinence and nonobstructive urinary retention, with over 325,000 patients implanted.¹ Satisfaction rates have consistently been high for patients in whom the therapy is effective.² However, complaints of implant site pain, poor cosmesis and limited battery life with the fixed-life device prompted manufacturers to introduce smaller, rechargeable battery systems to the market in 2020.

In addition to being smaller than their fixed-life counterparts, rechargeable devices promise to deliver a better cosmetic result with fewer trips to the operating room for battery replacement. These benefits come at the expense of needing to regularly recharge the device through an inductive charging process. This equates to more frequent patient-device interactions and introduces another piece of equipment for the patient to manage. While this may be a negligible inconvenience for most, patients who are less facile with new technologies or have a greater need for independence may find this bothersome.

Rechargeable device technology has been available for deep brain and spinal cord stimulation for over a decade. Data from studies done in these patient populations suggest that although many patients appreciated the smaller size of rechargeable devices, recharging could be a significant source of dissatisfaction. In a study of patients undergoing spinal cord stimulation for pain, 63% of patients had difficulty with coupling the charger to the battery and over half stated they would accept a larger battery if it did not require recharging.³ In a different study of deep brain stimulation, 19 of 30 patients chose a fixed-life device, citing a more convenient lifestyle as the biggest factor.⁴ While these patient populations and devices differ from those in the SNM space, these data do lend some insight into patient perceptions.

Since the real-world utilization of fixed-life (Interstim^TM II) and rechargeable (Interstim^TM Micro, Axonics^®) SNM systems has not been studied, we designed a prospective study at University of California, Los Angeles to investigate demographic differences in device selection and the long-term device specific satisfaction with each type of battery. Two separate ordinal scale surveys were administered. The first was administered after the patient chose device type. The second was administered 6 to 12 months after battery implantation and also included an open-ended question to explore patient concerns. We included patients undergoing device placement for all indications, but excluded those patients who had a strong indication for one device or another (eg multiple sclerosis patient with poor manual dexterity) and therefore were not able to choose between devices.

Preliminary results were analyzed from our first 35 patients. Perhaps not surprisingly given the small sample size, there was no significant difference in mean age, body mass index, gender, treatment indication, prior SNM or history of neurogenic bladder between the 2 battery types. While not statistically significant, patients who chose the fixed-life device tended to be older (68.1 vs 60.2 years, p=0.11) and to have a history of neurological disease (29% vs 10%, p=0.19). Flexibility was most often rated as “very important” to patients who chose the fixed-life device, while small device size and minimizing future surgeries seemed to be the most important to patients choosing the rechargeable battery.

When we followed up with patients after device implantation, all patients who reported improvement in their symptoms said they would recommend SNM to a friend or family member, regardless of battery type. However, when we looked more closely at device satisfaction, we noted some interesting findings. Half of the respondents who had a fixed-life device reported implant site pain “sometimes” or more often, compared to 10% of those with a rechargeable device. When it came to recharging, 3 of 10 patients reported connection issues between the battery and charger at least sometimes, and another 3 reported issues most of the time or always (fig. 1). When these 10 patients were asked if recharging the battery was easy, 2 patients were neutral and 1 disagreed. At least 2 patients reported some regret with choosing a rechargeable battery. Direct patient excerpts are cited in figure 2.

Some patient concerns raised in our study can certainly be mitigated with better education and reinforcement. Others need to be addressed with better technology and innovation. Specifically, improvements in inductive coupling will likely lessen frustration with the charging process. Smaller fixed-life batteries would likely reduce the risk of implant site pain or discomfort. Also, seemingly simple changes like making the lead interchangeable with both batteries would allow patients who are truly unhappy with one device to more seamlessly transition to another.

Figure 1. Response to survey question asking about coupling between device battery and the charger.

Figure 2. Select patient excerpts from device-specific satisfaction survey.

Both fixed-life and rechargeable devices play an important role in SNM. On first glance, patients may be attracted to a newer, smaller and thinner appearing rechargeable device. This is likely the right choice for patients whose priorities are cosmesis, minimizing implant site pain and avoiding future procedures. Other patients may actually feel recharging is cumbersome or that it interferes with their lifestyle. We find it helpful to use the available patient-facing informational pamphlets and videos to help our patients better understand what is involved with each technology. Another idea is setting up a patient registry so prospective SNM candidates can talk to patients with existing implants. Ultimately, it is the job of the surgeon to provide the appropriate counseling in order to best align the patient’s goals with the choice of technology and thereby optimize patient satisfaction.