Novel Wireless Battery-free Dural Implant for Chronic Motor Cortex Stimulation

Introduction: Brain neuromodulation has emerged as a viable therapeutic modality for various conditions, including movement disorders, epilepsy, stroke, trauma, and cancer. Current FDA-approved devices face significant limitations, such as lead migration, battery failures, and infection risks. To address these challenges, we developed a novel wireless, battery-free implant designed for intraoperative application over an FDA-approved commercial collagen dura substitute, allowing for continuous cortical stimulation without direct contact with the brain surface.

Methods: A wireless battery-free implant encapsulated in a 100 µm-thick, biocompatible, flexible, and transparent Parylene/PDMS substrate was used. The encapsulated implant was submerged in phosphate-buffered saline at 37°C for eight weeks to assess voltage output decay. The output voltage was compared before and after submersion. In vivo validation involved delivering wireless stimulation for five hours, using an external antenna to provide stimulation pulses (10 pulses, 100μs, 100Hz, 1 second intervals). Limb movement was monitored using a video analysis. After stimulation, histological analysis of the rat brains was done using H&E, GFAP, Olig2, and NeuN staining to evaluate the impact of stimulation on tissue integrity.

Results: Encapsulation reliability tests demonstrated that the MED1-4013 adhesive significantly reduced voltage decay, with only a 23.5% decrease in output voltage after eight weeks, indicating superior moisture resistance compared to parylene-C alone. In vivo stimulation effectively triggered motor responses, with measurable limb movements observed at transmit powers as low as 22 dBm. Histological evaluation revealed intact tissue architecture and no significant changes in differentiation patterns between stimulated and non-stimulated hemispheres, confirming the safety of the implant.

Conclusion : We demonstrate the efficacy and safety of the e-dura stimulation method, with no adverse tissue effects observed. The integration of wireless electronics on a dura substitute material shows revolutionary promise for chronic neuromodulation therapies. Future research will focus on optimizing the device for enhanced biocompatibility and exploring its long-term effects in clinical applications.