Future directions

Despite promising advances, integrating BSIs into standard clinical practice is fraught with technical, ethical, and logistical challenges. Importantly, current clinical evidence should be interpreted cautiously, as much of the existing literature remains proof-of-concept, preclinical, or based on single-patient reports and small cohorts. Although early studies have demonstrated encouraging improvements in voluntary movement, gait, and patient autonomy, these findings may not be broadly generalizable across the heterogeneous SCI population. Therefore, therapeutic claims regarding BSI, EES, DBS, regenerative therapies, and other emerging interventions should be interpreted according to the level of evidence supporting each approach, which ranges from preclinical proof-of-concept to small human cohorts and highly selected early clinical reports. Clinical translation will also require clearer patient selection criteria, particularly regarding injury level, completeness of injury, time since injury, preserved descending or propriospinal pathways, medical comorbidities, and ability to participate in intensive rehabilitation. The invasiveness of implanted cortical and spinal devices must also be weighed against potential functional benefit. Moreover, differences in injury level, completeness of injury, chronicity, residual neural circuitry, rehabilitation intensity, and device configuration may substantially influence outcomes. Additionally, the precision in recording and interpreting neural signals, the durability and safety of implantable devices, and the efficacy of non-invasive methods pose significant hurdles [57, 58]. Additionally, the implications of neural manipulation, patient consent, and the long-term impact of BSI use require careful consideration [59]. Long-term safety, durability of functional gains, device reliability, infection risk, hardware failure, and the need for revision procedures remain incompletely characterized. Furthermore, the extent to which BSI-mediated improvements persist after stimulation is discontinued, or translate into meaningful gains in activities of daily living, requires further investigation in larger prospective studies.

Logistically, the accessibility of BSI technology, cost implications, and the training of specialized personnel present additional barriers. Regulatory considerations, including device approval pathways, cybersecurity, data privacy, long-term monitoring, adverse-event reporting, and standards for explantation or device revision, will also be essential before widespread clinical implementation. Moreover, there is a pressing need to delve deeper into the patient’s perspective. Those who have undergone implantation of BSIs in clinical trials have reported experiencing heightened autonomy and a greater sense of self-control. However, contrasting experiences have been expressed, with some individuals describing postoperative feelings of detachment and challenges in integrating the implanted devices into their sense of self [59].

Future research should prioritize adequately powered clinical trials with standardized outcome measures, longer follow-up periods, and careful reporting of adverse events to better define patient selection criteria, reproducibility, and real-world clinical benefit. These challenges underscore the complexity of clinically incorporating BSI, highlighting the need for continued innovation to realize this technology’s full potential in transforming individuals’ lives.