1. Introduction

Deep brain stimulation (DBS) is an established treatment for managing motor symptoms in advanced Parkinson’s disease (PD) [1]. Recent advancements in battery technology have expanded the options for implantable pulse generators (IPGs) used in DBS, offering both rechargeable (r-IPGs) and nonrechargeable (nr-IPGs) devices [2]. Nr-IPGs are equipped with fixed-life batteries, typically lasting between 2 and 6 years depending on the intensity of stimulation and must be periodically replaced by a surgical intervention [3]. In contrast, r-IPGs require to be regularly recharged, but the potential lifespan exceeds 20 years (9–25 years) with proper maintenance. In clinical practice due to the absence of shared guidelines, the selection between the two is variable and depends on (1) patient-specific factors, such as lifestyle, overall health condition, cognitive status, age at intervention, and presence of a caregiver [4]; (2) clinicians’ expertise and personal attitude [4]; (3) DBS application such as the amount of current delivered [5]; and (4) economic factors [6]. Among all these, individual patient preferences play the most meaningful role in the shared decision-making process regarding IPG selection [5]. While numerous studies have examined patient concerns before implantation and their short-term satisfaction postintervention [2, 5, 7], there is limited knowledge about patients’ long-term experiences and satisfaction with the available IPGs, highlighting the need for further research on this topic.

2. Methods

3. Results

Interviews with completed clinical data were available for 80 PD-DBS patients among 94 patients followed in the time frame interval of 17 years from 2006 to 2022. Forty-three patients were r-IPG carriers, and 37 were nr-IPG carriers. Three nr-IPG of 37 carriers switched to r-IPGs after the first replacement. For the patients who switched, the interview was conducted prior to it (mean follow-up of 43 months) (flow chart, Figure 1). The survey was collected 85.3 (±32.0) months after DBS implant for nr-IPG and 73.1 (±37.7) months for r-IPG.

Demographic and clinical data are presented in Table 1. No significant differences were detected between groups for sex (19 males for nr-IPG vs. 30 for r-IPG), years of disease at surgery (12.4 ± 4.9 vs. 12.0 ± 4.0) and at last follow-up (19.9 ± 5.5 vs. 18.0 ± 4.8), pre-DBS On-medication MDS-UPDRS III (26.0 ± 6.3 vs. 23.2 ± 9.4) and IV (5.9 ± 3.9 vs. 6.3 ± 2.6), pre-DBS LEDD (870.0 ± 396.0 mg vs. 1053.1 ± 580.3 mg), and last follow-up LEDD (749.4 ± 276.4 mg vs. 695.5 ± 331.2 mg). Significant differences were present for age at intervention (63.6 ± 7.0 years for nr-IPG carriers vs. 54.8 ± 6.9 years for r-IPGs) and at follow-up (70.9 ± 6.7 years vs. 60.8 ± 7.2 years) and MDS-UPDRS III (25.8 ± 8.4 vs. 19.9 ± 8.1), MDS-UPDRS IV (4.5 ± 3.8 vs. 2.3 ± 2.0), and H&Y (3.3 ± 0.6 vs. 2.7 ± 0.5) at the moment of the survey.

Answers to the interview are summarized in Tables 2, 3, and 4. At the time of the survey, the majority of patients (93.0% of r-IPGs vs. 83.8% of nr-IPGs) were satisfied with their DBS implant. One hundred percent of r-IPGs and 75.7% of nr-IPGs (p = 0.001) were globally satisfied with their IPGs. Ninety-five percent of r-IPGs and 45.9% of nr-IPGs (p < 0.001) would have chosen again the same type of IPG. 97.7% of r-IPGs and 64.9% of nr-IPGs would recommend their type of IPG (p = 0.001). Furthermore, patients in both groups claim that the size of the IPG was too big (16.2% in nr-IPGs and 4.2% in r-IPGs, p = 0.086).

Regarding the long-term experience of r-IPG patients, 97.7% do not find it difficult to recharge the battery, and 81.4% claim to do so autonomously. Furthermore, 86.0% have never forgotten to recharge the battery. Most of the patients recharge the battery every 2 weeks (46.5%) for an estimated time between 1 and 2 h (67.5%). The time of the recharge did not impact on everyday life for almost the totality of the patients (97.7%). Referring to the recharge system, 32.6% experienced malfunctioning problems, with the majority concerning the charge-IPG matching (23.3%) and the remote control malfunction (21.0%). Among nr-IPG carriers, 48.6% still expressed concerns about undergoing interventions for IPG replacements.

A higher number of complications after the first DBS implant (13 vs. 5, p < 0.05) and during subsequent admissions for the IPG substitutions (4 vs. 0, p < 0.05) were detected in the nr-IPG group compared to r-IPGs. Among these, infective complications of IPG (five for nr-IPGs and one for r-IPGs) and complications due to malfunction of the IPG (three for nr-IPGs and two for r-IPGs) or unpredictable battery depletion (two for nr-IPGs) were the most numerous. Among the latter, one case of withdrawal syndrome required a brief hospitalization. In seven cases among nr-IPG carriers, an early intervention of substitution was necessary. Surgical revision of the IPG was performed in six patients (three with nr-IPG and three with r-IPG), while lead drainage was carried out in three patients with nr-IPG. The overall IPG infection rate for all surgical procedures in nr-IPGs was 4.8%, and in r-IPGs, it was 2.3%. Three out of five nr-IPG infections occur after the initial implantation within a period of 28 to 50 months following surgery, while others occur within 3 months after the first replacement, which was performed regularly due to the end of life of the battery.

No infective complications of IPG were detected in the nr-IPG sample after the second or subsequent replacements (3/37 after implant, 2/36 after I replacement, and no cases for II, III, and IV replacements). Other intercurrent complications observed in the cohort (infection of the DBS leads, resurgical procedures for mispositioning, and idiopathic delayed-onset edema) do not appear to be directly attributable to the IPG. During hospitalization for IPG substitutions in the nr-IPG group, two patients developed delirium, one complicated with sepsis, and one presented an adverse reaction to prophylactic antibiotics.

The number of total amounts of hospitalization days, considering replacements and complications, was significantly higher for the nr-IPG group compared to the r-IPG group (19.6 ± 9.9 vs. 9.3 ± 4.8, p < 0.001). No differences concerning the presence of stimulation-induced complications during the outpatient monopolar revision and DBS parameter fine-tuning within the first 6 months after surgery were detected between groups (28 for nr-IPGs and 33 for r-IPGs, p = 0.911). Data about care load and complications during or after hospitalization are shown in Figure 2.

The choice between remaining with nr-IPG and switching to a r-IPG was offered before a subsequent substitution to 14 patients, and 3 of them accepted. Of the 11 remaining patients, 6 refused fearing not to be able to recharge, 3 for a personal preference, and 2 considering r-IPG incompatible with their lifestyle (many travels for business).

In Figure 3a, a survey on clinician perspective of switching or not to r-IPG is reported. Data are available for 23 patients out of 34. The remaining patients (11/34) underwent replacements or passed away before the r-IPG became commercially available. Advanced age (patients > 70 years old) was determinant for not proposing the switch in 47.8% (11/23) of cases examined by the clinician, while the absence of caregivers or inadequate care setting accounted for 21.8% (5/23), the presence of cognitive decline (MCI or dementia) for 13.0% (3/23), and a poor prognosis at 12 months for 17.4% (4/23). In Figure 3b, patient’s perspective on not switching is reported (data inferred from the interviews of patients who were offered to switch and choose to keep nr-IPG and those who stated they were satisfied with their current nr-IPG device and would not have wanted to switch). Fear of not being able to recharge was determinant in 57.2% (12/21) of patients, and lifestyle consisting of many travels for business in 9.5% (2/21). A personal preference for the nr-IPG device accounted for 33.3% (7/21).

4. Discussion

A significant emphasis on making choices based on individual focusing has been placed in selection criteria for proposing DBS to patients with PD to ensure the best clinical outcomes after the intervention [11]. Important in this patient-centered paradigm is the choice between r-IPG and nr-IPG proposed by physicians [4], who play a crucial role in highlighting the most significant factors (clinical, organizational, and economical) to be considered in this decision-making process [12].

Referring to patient’s perspective, many works in the literature report on patient’s satisfaction with their IPG after short-term intervals of 3–6 months [13, 14], 12 months [15], or medium-term interval (18–42 months) [2, 5, 16–18] post-DBS implant. Only one study evaluated a longer follow-up (40.3 ± 24.8 months [18]) but solely for r-IPG carriers (see Table 5 for review).

Data on long-term experiences with r-IPG and nr-IPG are lacking [13], and to the best of our knowledge, this is the first study to assess the real-life long-term experiences and satisfaction of patients with r-IPG and nr-IPG.

Consistent with previous short- and mid-term follow-up findings [2, 13, 17], the majority of patients in our study reported high overall satisfaction with their IPG after long-term follow-up, regardless of the device type. In a Chinese cohort, Qiu et al. observed similar satisfaction levels between r-IPG users (88%) and nr-IPG users (83%) after 18 months of DBS therapy [2]. Timmerman et al. [13] and Hitti et al. [18] both found a sustained preference for r-IPGs among patients who had switched from an nr-IPG, with evaluations conducted 3 months (seven patients, 75%) and 2 years (83 patients, 70.3%) postsurgery, respectively. A widening gap in satisfaction levels over the long term, with higher satisfaction among r-IPG users (100%) and slightly lower satisfaction among nr-IPG users (75.7%), has been detected in our survey. It is unclear whether this difference reflects a gradual divergence over time or is due to differing characteristics between the two populations which could significantly affect the results (see Table 1).

Our findings on the long-term experience of using r-IPGs align with previous studies that assessed the sustainability of the recharging process and the complications encountered during short-term follow-up [2, 15, 18]. Recharging time and frequency are consistent with Jakobs et al.’s findings (IPG recharge every 10 ± 8 days for 97 ± 57 min), showing stability even over the longer term [19]. Furlanetti et al. demonstrated that patients who were well-informed and had realistic expectations before surgery did not experience a change in concerns about recharging postoperatively [5]. Our results confirm that this trend continues even many years after implantation, indicating that fears of discomfort with the recharging process are not borne out in patients’ long-term experiences. Differently from previous suggestions, increasing time burden of recharging over the years might not impact patient satisfaction [18]. The incidence of technical device-related issues in our r-IPG cohort mirrors that of a previous study by Mitchell et al. (32.6% vs. 35.6%) [14], suggesting that the rate of hardware-related adverse events for r-IPGs remains stable over time. Finally, in contrast to Qiu et al. [2], who reported that 89% of r-IPG users abstained from work and 73% from travel due to the recharging process, our r-IPG carriers did not report any restrictions in their daily activities, including work.

Fear of multiple replacement surgeries and the size of the IPG have been identified as significant factors contributing to dissatisfaction with nr-IPGs, especially as concerns that emerge over time following implant surgery [5, 7]. However, even if these factors remain issues for our nr-IPG group, our survey demonstrated that the level of satisfaction is consistently high, thus not appearing to be affected by such concerns even if still present. Furthermore, the majority of patients in our population who were offered the possibility chose not to switch to a r-IPG still maintaining a high level of satisfaction with their nr-IPGs.

In our cohort (Figure 3a), advanced age (> 75 years) emerged as one of the most significant factors influencing the decision of clinicians not to recommend a switch to a r-IPG (47.8%), and cognitive impairment prevented the proposal of switching to an r-IPG in 13.0% of cases involving nr-IPG carriers. Indeed, supporting these positions, satisfaction was sustained among those who retained the nr-IPG without being offered to switch.

On the other side, Timmermann et al. suggested a role of age in r-IPG satisfaction, detecting a lower degree of satisfaction among elderly patients about the recharging process [13]. However, studies in r-IPGs have not identified a direct role of age on the adaptability to the recharge [2, 19], and these data also appear to be supported by our observations over the clinical follow-up period, considering the adherence and ease of handling of the recharging process as reported by patients. Differently, it is not possible to draw any indication of the effect of cognitive decline in this decision-making process because all the available studies conducted on IPG carriers, as our work, enrolled those patients who preserved global cognitive functions during follow-ups [18, 19] and real data in patients with severe cognitive decline are lacking. Regardless of cognitive impairment, akin to Qiu et al. [2], our r-IPG carriers who declared recharging process concerns were successfully assisted by a caregiver without reported decreased satisfaction in this choice.

Another crucial factor in choosing between different types of devices for DBS carriers is the clinical and ethical considerations regarding DBS in end-stage PD [20]. In our observation, poor prognosis at 12 months was a key reason (17.4% of cases) for maintaining a nr-IPG. Patients who have reached advanced stages of the disease or developed significant comorbidities may still benefit from DBS, and abruptly discontinuing treatment could lead to serious consequences [21]. For that reason, the management of IPG replacement in these cases is still debated, and therapy discontinuation strategies are not always feasible. Traditionally, advanced age and late-stage PD with dementia have been reasons to prefer nr-IPGs to reduce the caregiving burden on patients. To corroborate this, evidence shows that surgical replacement has proven to be relatively safe at this stage [22]. On the other hand, previous research has demonstrated that caregivers can effectively handle the recharging of r-IPGs without affecting satisfaction levels or complication rates [19]. Therefore, a robust social and healthcare support network could make r-IPGs as well beneficial for patients in the later stages of the disease, potentially reducing the risk of multiple surgeries.

It is important to emphasize that the data and considerations presented here do not aim to establish the superiority of one type of IPG over the other, but rather to align with current trends in DBS of promoting careful case-by-case assessment rather than strict indications [11] even in the IPG choice. The majority (89.2%) of nr-IPG users in our study had their first DBS implantation between 2006 and 2011 when r-IPGs were not yet available in our country (r-IPGs became available at our hospital in 2012); for this reason, despite the aforementioned limitations, the data appear to be more reliable only for assessing satisfaction in absolute terms. These patients were likely offered the opportunity to eventually switch to r-IPGs during subsequent replacements, but by that time, they were older and less independent, which probably influenced their decision to stick with the IPG type they were familiar with, as demonstrated by the fact that concerns about the recharging process were a key factor for 57.2% of nr-IPG patients who chose not to switch (Figure 3b). Furthermore, the two samples from the DBS population were not homogeneous in certain baseline aspects. The age at the time of intervention and the disease severity were significantly lower in the r-IPGs group; this is likely due to a gradual shift in eligibility criteria for DBS together with a progressive increase in expertise, which resulted in the selection of patients at less advanced stages of the disease. In particular, it is highly plausible that age at the time of implantation may have influenced patients’ expectations and, consequently, their level of satisfaction, as well as contributed to a subjective variation in what is perceived as acceptable when assessed at follow-up compared to baseline. Moreover, although there are no differences in LEDD at baseline and follow-up between groups, a more pronounced reduction is observed in the r-IPG group, and its possible contribution to a higher degree of satisfaction cannot be excluded. Finally, a possible subjective preference of patients for different manufacturers was not assessed. These elements indeed make it impossible to assess a fully reliable comparison of the satisfaction levels reported between the two IPGs, which, in any case, is not among the objectives of the study.

In our cohort, IPG infection was the most meaningful complication after DBS implant with an incidence during all surgical procedures of 4.08%, as in line with previous studies (ranging from 2.01% to 6.4%) [19, 23–26]. Comparing the IPG types, akin to Frizon et al. [26], we confirmed a lower infection rate in r-IPG than in nr-IPG, although the latter showed a decreasing trend during the subsequent IPG replacements. These data are not in line with previous reports which have shown an increasing rate of infections with the number of replacement procedures [23–25, 27] Similarly, a higher rate of complications during hospitalization for IPG replacements was detected in nr-IPG groups (4 vs. 0). A limitation due to the progressive improvement of surgical techniques, care practices, and technologies over the years constrains the interpretation of the analyses reported here. Although part of the surgical procedures and complications analyzed in the study occurred after both types of IPG were introduced to the market, some of the initial implant procedures took place during a period when only one type of IPG (NR) was available, lacking a control sample. Taking these limitations into account, our data on long-term follow-up seems to confirm literature data of more favorable outcomes in r-IPG over nr-IPG because of fewer clinical risks (withdrawal syndrome after IPG exhaustion or sudden failure), less infective risk, and less hospitalization stay and cost [28–30].

In addition to the retrospective nature of this study, the monocentric design restricted the number of patients analyzed. Lastly, patient satisfaction and experience were assessed from a subjective qualitative point of view due to the absence of a validated scale for these evaluations, and the progressively increasing dropout rate among Nr-IPG carriers prior to the commercial availability of rechargeable devices may have affected the results.

5. Conclusion

Long-term observations show that the overall satisfaction with IPGs among DBS carriers remains stable, although r-IPG users report higher satisfaction. The discomfort associated with recharging is likely to be less of a factor when evaluating IPG choices, and the need for multiple surgeries for battery replacements and the size of the device, even if it could still be an issue, do not affect satisfaction with nr-IPGs over time. Whenever possible, optimal shared decision-making involves offering patients a choice between r-IPGs and nr-IPGs to enhance patient satisfaction and adherence to treatment. Additionally, r-IPGs are associated with fewer complications and shorter hospital stays, even in long-term evaluations.

Further studies on the long-term assessment of IPG carriers are needed to better identify individuals who may benefit more from different types of IPG, and observational analysis on long-term experience is required to determine whether clinicians should consider factors like age, cognitive decline, and support networks holistically rather than in isolation when advising on IPG options.

Ethics Statement

We confirm that we have read the journal’s position on issues involved in ethical publication and affirm that this work is consistent with those guidelines.

Conflicts of Interest

Mariachiara Sensi receives speaking honoraria from AbbVie, Boston Scientific, and Bial. She receives advisory board fees from Bial. All other authors report no conflict of interest or disclosures.

Author Contributions

Conceptualization: Pietro Antenucci, Mariachiara Sensi; data collection and methodology: Pietro Antenucci, Fabiana Colucci; analysis and interpretation of results: Pietro Antenucci, Ilaria Casetta, Mariachiara Sensi; writing—original draft preparation: Pietro Antenucci; writing—review and editing: Mariachiara Sensi, Ilaria Casetta; supervision: Fabiana Colucci, Mariachiara Sensi. All authors reviewed the results and approved the final version of the manuscript.

Funding

No funding was received for this manuscript.