Design of an adaptable intrafascicular electrode (AIR) for selective nerve stimulation by model-based optimization

Abstract

Peripheral nerve stimulation is being investigated as a therapeutic tool in several clinical scenarios. However, the adopted devices have restricted ability to obtain desired outcomes with tolerable off-target effects. Recent promising solutions are not yet employed in clinical practice due to complex required surgeries, lack of long-term stability, and implant invasiveness. Here, we aimed to design a neural interface to address these issues, specifically dimensioned for pudendal and sacral nerves to potentially target sexual, bladder, or bowel dysfunctions. We designed the adaptable intrafascicular radial electrode (AIR) through realistic computational models. They account for detailed human anatomy, inhomogeneous anisotropic conductance, following the trajectories of axons along curving and branching fascicles, and detailed biophysics of axons. The model was validated against available experimental data. Thanks to computationally efficient geometry-based selectivity estimations we informed the electrode design, optimizing its dimensions to obtain the highest selectivity while maintaining low invasiveness. We then compared the AIR with state-of-the-art electrodes, namely InterStim leads, multipolar cuffs and transversal intrafascicular multichannel electrodes (TIME). AIR, comprising a flexible substrate, surface active sites, and radially inserted intrafascicular needles, is designed to be implanted in a few standard steps, potentially enabling fast implants. It holds potential for repeatable stimulation outcomes thanks to its radial structural symmetry. When compared in-silico, AIR consistently outperformed cuff electrodes and InterStim leads in terms of recruitment threshold and stimulation selectivity. AIR performed similarly or better than a TIME, with quantified less invasiveness. Finally, we showed how AIR can adapt to different nerve sizes and varying shapes while maintaining high selectivity. The AIR electrode shows the potential to fill a clinical need for an effective peripheral nerve interface. Its high predicted performance in all the identified requirements was enabled by a model-based approach, readily applicable for the optimization of electrode parameters in any peripheral nerve stimulation scenario.

Biomimetic computer-to-brain communication enhancing naturalistic touch sensations via peripheral nerve stimulation

“…We believe that neurostimulation strategies should be informed by computational modeling, which emulates realistic dynamic conditions. Moreover, we envision the usage of machine learning methods for calibrating the system 89 and predicting the most suitable stimulating pattern, together with the design of more advanced electrodes 90 . In addition to the here-presented benefit, we hypothesize that this restored natural feedback would have a positive impact on the level of incorporation of this artificial device.…”

Clinical outcomes of peripheral nerve interfaces for rehabilitation in paralysis and amputation: a literature review

“…The adaptable intrafascicular radial electrode (AIR) was specifically designed for pudendal and sacral nerves to target sexual, bladder, or bowel dysfunctions. AIR electrodes demonstrated high selectivity, low invasiveness, faster implants, repeatable stimulation, and the ability to adapt to different nerve sizes and shapes compared to other electrodes [84].…”