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Stent-electrode recording array
Stent-electrode recording array
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The Stentrode device

Stentrode (Stent-electrode recording array) is a small stent-mounted electrode array permanently implanted into a blood vessel in the brain, without the need for open brain surgery. It is in clinical trials as a brain–computer interface (BCI) for people with paralyzed or missing limbs,[1] who will use their neural signals or thoughts to control external devices, which currently include computer operating systems. The device may ultimately be used to control powered exoskeletons, robotic prosthesis, computers or other devices.[2]

The device was conceived by Australian neurologist Thomas Oxley and built by Australian biomedical engineer Nicholas Opie, who have been developing the medical implant since 2010, using sheep for testing. Human trials started in August 2019[3] with participants who suffer from amyotrophic lateral sclerosis, a type of motor neuron disease.[1][4] Graeme Felstead was the first person to receive the implant.[5] To date, eight patients have been implanted and are able to wirelessly control an operating system to text, email, shop and bank using direct thought through the Stentrode brain computer interface, marking the first time a brain-computer interface was implanted via the patient's blood vessels, eliminating the need for open brain surgery.

The FDA granted breakthrough designation to the device in August 2020.[6] In January 2023, researchers demonstrated that it can record brain activity from a nearby blood vessel and be used to operate a computer with no serious adverse events during the first year in all four patients.[7][8]

Overview

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Opie began designing the implant in 2010, through Synchron, a company he founded with Oxley and cardiologist Rahul Sharma.[9] The small implant is an electrode array made of platinum electrodes embedded within a nitinol endovascular stent. The device measures about 5 cm long and a maximum of 8 mm in diameter.[10] The implant is capable of two-way communication, meaning it can both sense thoughts and stimulate movement, essentially acting as a feedback loop within the brain, which offers potential applications for helping people with spinal cord injuries and control robotic prosthetic limbs with their thoughts.[11][12][13]

The Stentrode device, developed by Opie and a team at the Vascular Bionics Laboratory within the Department of Medicine at the University of Melbourne,[14] is implanted via the jugular vein into a blood vessel next to cortical tissue near to the motor cortex and sensory cortex, so open brain surgery is avoided.[15] Insertion via the blood vessel avoids direct penetration and damage of the brain tissue. As for blood clotting concerns, Oxley says neurologists routinely use permanent stents in patients' brains to keep blood vessels open.[15] Once in place, it expands to press the electrodes against the vessel wall close to the brain where it can record neural information and deliver currents directly to targeted areas.[10] The signals are captured and sent to a wireless antenna unit implanted in the chest, which sends them to an external receiver. The patient would need to learn how to control a computer operating system that interacts with assistive technologies.

The Stentrode technology has been tested on sheep and humans, with human trials being approved by the St Vincent's Hospital, Melbourne Human Research Ethics Committee, Australia in November 2018.[16][4] Oxley originally expressed that he expected human clinical trials to help paralyzed people regain movement to operate a motorized wheelchair or even a powered exoskeleton.[10] However, he switched focus before beginning clinical trials. Opie and colleagues began evaluating the Stentrode for its ability to restore functional independence in patients with paralysis, by enabling them to engage in activities of daily living.[17] Clinical study results demonstrated the capability of two ALS patients, surgically fitted with a Stentrode, to learn to control texting and typing, through direct thought and the assistance of eye-tracking technology for cursor navigation.[18] They achieved this with at least 92% accuracy within 3 months of use, and continued to maintain that ability up to 9 months (as of November 2020).[18] This study helped to dispel some criticism that data rates may not be as high as systems requiring open brain surgery, and also pointed out the benefits of using well-established neuro-interventional techniques which do not require any automated assistance, dedicated surgical space or expensive machinery.[citation needed]

Selected patients are people with paralyzed or missing limbs, including people who have suffered strokes, spinal cord injuries, ALS, muscular dystrophy, and amputations.[15][10]

See also

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References

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Stent-electrode recording array

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A stent-electrode recording array, also known as the Stentrode, is a minimally invasive endovascular neural interface device comprising a self-expanding nitinol stent integrated with an array of platinum-iridium electrodes embedded on a polyimide substrate, designed for chronic, high-fidelity recording of cortical neural activity directly from within cerebral blood vessels without requiring open-brain surgery. This technology enables the capture of broadband neural signals, including local field potentials and action potentials, by positioning the device adjacent to targeted brain regions such as the motor cortex via catheter-based delivery through the jugular vein. Developed as a brain-machine interface (BMI) alternative to traditional invasive electrodes, the Stentrode facilitates thought-controlled digital interactions for individuals with severe paralysis, transmitting signals wirelessly via an implanted telemetry unit to external devices, with recent integrations of generative AI features by Synchron enabling enhanced signal interpretation and output generation, such as text and audio from thoughts. The Stentrode's development originated from DARPA-funded research at the University of Melbourne's Vascular Bionics Laboratory, with initial preclinical demonstrations in sheep models in 2016, where it recorded stable neural activity for up to 190 days with signal quality comparable to epidural arrays and preserved vascular patency. Subsequent advancements by Synchron Inc. refined the design, incorporating 16 channels for improved , and led to the first-in-human implantations starting in 2019 as part of the SWITCH study, targeting patients with (ALS) or primary lateral sclerosis. Systematic reviews have confirmed its efficacy in signal detection and decoding, achieving accuracies up to 70% in motor intent prediction, while highlighting its evolution from early prototypes to a fully implantable system. Implantation involves a neurointerventional procedure under , deploying the 6-mm diameter device into the or cortical veins overlying the , where it endothelializes within 28 days to integrate with the vessel wall, minimizing risks like through antiplatelet therapy such as aspirin. In clinical trials like SWITCH, involving four patients followed for 12 months, the device demonstrated no serious adverse events, no vessel occlusions, and enabled hands-free control of computers for tasks such as texting and emailing, with mean selection accuracies of 93.9% and stable signal bandwidths averaging 233 Hz. These outcomes underscore its safety profile, with mean procedure times of 232 minutes (range, 179-298 minutes) and compatibility with outpatient settings, contrasting sharply with the morbidity of craniotomy-based alternatives. The COMMAND trial, completed in 2024, demonstrated safety and efficacy in six patients with no serious adverse events and reliable motor signal capture, paving the way for a pivotal study as of . As of , the technology has been integrated natively with consumer devices like Apple's , , and Vision Pro, and recognized as one of TIME's Best Inventions of 2025, with over 10 patients implanted across trials. Despite limitations like lower compared to intracortical arrays and challenges in deep brain targeting, the technology's minimally invasive nature positions it as a scalable platform for BMIs, with future directions focusing on material optimizations (e.g., coatings) and expanded human studies to validate efficacy across diverse patient populations.

Introduction

Definition and Purpose

The stent-electrode recording array, commonly known as the stentrode, is a self-expanding, endovascular device that integrates a framework with platinum-iridium arrays, designed for permanent implantation in cerebral veins to enable the recording of neural signals from adjacent cortical tissue. This minimally invasive neural interface captures vascular () signals, including , without requiring direct penetration of parenchyma. The primary purpose of the stentrode is to facilitate high-resolution, long-term neural recording for brain-machine interfaces (BMIs) and diagnostic monitoring of neurological conditions, thereby minimizing the risks associated with traditional open-brain surgical procedures such as and . By decoding cortical activity, it supports applications like thought-controlled digital switching and motor restoration in patients with or severe motor impairments. As of 2025, ongoing trials like COMMAND continue to demonstrate long-term signal stability over one year in additional patients. Uniquely, the device targets cerebral vasculature, such as the or superficial cortical veins, to access regions like the indirectly through the vessel walls, leveraging the proximity of veins to the brain surface for signal acquisition. Its feasibility for chronic use was first demonstrated in a 2016 ovine model, where it enabled stable recordings of endogenous neural activity in freely moving sheep for up to 190 days.

Comparison to Traditional Neural Interfaces

Traditional neural interfaces, such as subdural grids, depth electrodes, and microelectrode arrays like the Utah array, typically require invasive surgical procedures involving or burr hole placement to access the brain tissue directly. These methods expose patients to significant risks, including infection rates of approximately 7.9% per patient for subdural grid implantations and potential tissue damage from mechanical disruption of neural structures during penetration. In contrast, the stent-electrode recording array employs an endovascular approach, deployed via catheterization through the vascular system—often the —without opening the skull or penetrating brain parenchyma. This method utilizes the lumen for access and relies on the device's self-expanding nitinol framework to achieve a conformal fit against the vessel walls, reducing the need for active fixation and minimizing acute tissue trauma. As a result, it bridges the gap between non-invasive techniques like scalp EEG, which offer limited signal resolution, and fully invasive arrays, providing chronic access with a safer profile. Regarding signal quality, the stent-electrode array records broadband neural signals, including and gamma-band activity up to approximately 300-500 Hz, from distances of 260-680 µm through the vascular . Its signal-to-noise ratios (SNRs) are comparable to those of cortical surface electrodes, achieving values around 18-20 dB for evoked potentials in motor and visual areas, sufficient for decoding movement intentions in brain-machine interfaces. While penetrating arrays like the Utah array offer higher and single-unit activity, the endovascular design trades some acuity for reduced invasiveness without substantial loss in overall fidelity for population-level signals. For longevity, the stent-electrode array is engineered for indefinite implantation, with stable recordings demonstrated up to 12 months in early human trials and follow-up showing stability up to 34 months as of 2023, secured by neointimal hyperplasia that integrates the device into the vessel wall without eliciting severe . Traditional invasive interfaces, however, often experience signal degradation within months to years due to chronic inflammatory responses, encapsulation, and around penetrating electrodes, limiting their utility for long-term applications.

History and Development

Invention and Early Research

The stent-electrode recording array, known as the Stentrode, was invented by neurologist Thomas J. Oxley and biomedical engineer Nicholas L. Opie, along with colleagues at the University of Melbourne's Vascular Bionics Laboratory, in collaboration with Synchron Inc.. The device addressed key limitations in existing brain-machine interfaces (BMIs) for patients with severe , such as the high risks of infection and tissue damage associated with invasive procedures like (ECoG) that require .. Motivated by the proven biocompatibility and minimally invasive deployment of cardiac and neurovascular stents, the inventors sought to develop an endovascular alternative capable of chronic neural recording to benefit individuals with and (ALS), enabling potential restoration of communication and mobility through thought-controlled devices.. This approach was inspired by Oxley's clinical experience with stent retrievers for clot removal in patients, highlighting the feasibility of integrating electrodes into self-expanding vascular stents.. Early preclinical research, conducted from 2013 to 2015, emphasized evaluating the device's and signal-recording capabilities in animal models, including assessments of endothelial integration and long-term stability within cerebral veins.. These studies demonstrated that the Stentrode could achieve high-fidelity recordings of cortical neural activity comparable to traditional surface arrays, with signals maintained chronically for up to 190 days without significant degradation or adverse vascular effects.. The foundational proof-of-concept was established in the landmark 2016 publication in Nature Biotechnology, which reported successful ovine implantations via the , confirming the device's ability to record in sheep.. This work was supported by DARPA's Reliable Neural-Technology (RE-NET) program, which funded efforts to advance safer neural interfaces.. SmartStent, the predecessor to Synchron Inc., was founded in 2012 by Oxley and Opie to commercialize the technology and translate it from laboratory prototypes to clinical applications; it was renamed Synchron in 2016.. Initial patents protecting the Stentrode's design and deployment methods were filed starting in 2010, with key provisional applications submitted around 2014 to secure intellectual property for the endovascular electrode array..

Key Milestones and Funding

The stent-electrode recording array, initially developed by a team led by Thomas Oxley at the University of Melbourne, received early financial support from the U.S. Defense Advanced Research Projects Agency (DARPA) through its Reliable Neural-Interface Technology (RE-NET) program, which funded foundational research from 2010 onward. This backing enabled preclinical advancements, including a $10 million investment in Synchron in 2017 to support clinical trials. A pivotal milestone occurred in 2016 with the first chronic ovine study, which demonstrated high-fidelity neural recordings from the for up to 190 days in freely moving sheep, confirming the device's long-term stability without open-brain surgery. Building on this, a 2019 sheep study showcased the array's capability to decode signals for prosthetic limb control, achieving reliable detection of imagined movements with signal quality comparable to invasive arrays. The first human implantation took place in in 2019 as part of the SWITCH study, where the device was deployed endovascularly to enable thought-controlled digital switching in patients with . Regulatory progress accelerated in 2020 with FDA Breakthrough Device Designation for brain-machine interface applications in individuals with severe or communication deficits. Further funding sustained translation to clinical use, including a $10 million grant from the (NIH) in 2021 to launch the U.S.-based COMMAND trial evaluating the device in patients. The Australian National Health and Medical Research Council (NHMRC) provided AUD $1.5 million in 2020 to advance commercialization through university collaborations. Synchron raised over $75 million from private investors by 2023, highlighted by a $75 million oversubscribed Series C round in December 2022 led by ARCH Venture Partners, bringing the company's total funding at that time to $145 million. In November 2025, Synchron raised $200 million in an oversubscribed Series D round, led by Double Point Ventures, bringing the total funding to $345 million as of that date. In 2023, the COMMAND early feasibility trial initiated patient enrollment at multiple U.S. sites, marking the device's expansion for therapeutic applications in severe motor impairment. By October 2024, the COMMAND trial had enrolled six patients, demonstrating successful deployment, stable signal recording, and enabling hands-free digital interactions with no serious adverse events reported.

Design and Components

Structural Features

The stent-electrode recording array, commonly known as the Stentrode, features a cylindrical architecture based on a nitinol (nickel-titanium) stent scaffold, which serves as the primary structural framework for endovascular deployment. This self-expanding , leveraging the shape memory properties of nitinol, deploys to conform closely to the walls of target blood vessels, such as cerebral veins, without requiring active inflation mechanisms like balloons. The deployed dimensions typically measure approximately 40 mm in length and 8 mm in diameter, optimized for anatomical fit in vessels like the . Platinum-iridium electrodes are lithographically patterned on a flexible substrate and adhesively bonded or wrapped around the luminal surface of the stent's struts, ensuring stable integration while preserving the scaffold's superelasticity. Biocompatibility is enhanced through material selections and design elements that promote endothelialization and minimize adverse vascular responses. The nitinol , insulated with parylene-C, facilitates rapid tissue ingrowth, achieving full endothelial coverage within about 28 days in preclinical models, which helps anchor the device and reduce risks like micromotion or excessive formation. To mitigate , patients receive dual antiplatelet therapy (e.g., aspirin and clopidogrel) for at least 90 days post-implantation, supporting long-term patency observed up to 190 days in ovine studies. Radiopaque markers integrated into the enable precise fluoroscopic guidance during deployment, ensuring accurate positioning without compromising the device's structural integrity. The design supports for various vessel sizes, with early prototypes featuring 16 electrodes arranged along the stent struts at intervals of about 2.5 mm to target specific cortical regions. This modular architecture allows adaptation for different neurovascular anatomies while maintaining the core self-expanding form factor. The overall structure facilitates chronic neural signal recording by positioning electrodes in close proximity to cortical tissue through the vessel wall, though detailed signal performance is addressed elsewhere.

Electrode Array Specifications

The electrode array in a stent-electrode recording array, such as the Stentrode developed by Synchron, features 16 -iridium disc electrodes, each approximately 500 μm in diameter, lithographically patterned onto a flexible substrate and mounted along the struts of a self-expanding nitinol stent. Earlier prototypes utilized 8 disc electrodes of 750 μm diameter on a similar substrate. These electrodes demonstrate impedance characteristics of 10–50 kΩ at 1 kHz following endothelialization, facilitating low-noise recording of neural signals, with oxide coatings on the platinum- (80:20 or 90:10 ratio) surfaces to enhance charge injection limits for potential future stimulation applications. The array supports bipolar or monopolar configurations, with electrodes spaced 2–3 mm apart circumferentially along the stent's luminal surface to span relevant cortical regions without excessive , insulated by parylene-C traces. Neural signals are recorded across a bandwidth optimized for and multi-unit activity, typically 0.3–400 Hz, with sampling rates up to 2 kHz, and transmitted wirelessly via to an external or subcutaneous receiver unit.

Implantation Procedure

Endovascular Deployment

The endovascular deployment of a stent-electrode recording array, such as the Stentrode, is a minimally invasive neurointerventional procedure performed under general in a hybrid angiography suite to position the device within cerebral veins overlying targeted brain regions. Access is gained percutaneously via the using a modified , with a 9 French introducer sheath inserted to facilitate navigation. Dual antiplatelet therapy, typically aspirin and clopidogrel, is initiated 2 weeks prior to mitigate risk during the procedure. The procedure begins with preoperative imaging, including MRI and CT venography, to map the venous anatomy and identify the target site, such as the superior sagittal sinus adjacent to the precentral gyrus for motor cortex recording in brain-machine interface applications. A guide catheter is advanced through the jugular bulb into the superior sagittal sinus under biplanar fluoroscopy and digital subtraction angiography (DSA) guidance, often with MRI-venography fusion overlays for enhanced precision. Next, a microcatheter (approximately 2 French or 0.021-inch inner diameter) supported by a 0.014-inch guidewire is navigated to the deployment site, allowing angiographic mapping of the target vein via contrast injection for venography. The compressed stent-electrode array, preloaded within the delivery system akin to flow diverter stents, is then positioned precisely. Deployment occurs by retracting the outer sheath, enabling the self-expanding nitinol-based (typically 8 mm × 40 mm) to anchor against the while integrating the for neural signal capture. Confirmation involves immediate DSA and cone-beam CT to verify positioning and coverage of the target cortical area, supplemented by intraoperative impedance testing of the channels and initial neural signal recording. A transvenous lead is tunneled subcutaneously to connect the to an implantable receiver unit in the infraclavicular region. The entire procedure typically lasts 90–120 minutes, with the endovascular phase requiring less than 30 minutes of time, though total operative time can extend to a mean of 232 minutes including testing. In clinical trials, successful deployment with accurate coverage has been achieved in 100% of cases across multiple patients.

Integration with Vascular System

Following implantation via endovascular deployment, the stent-electrode recording array undergoes a natural endothelialization process in which the device's struts and electrodes become encapsulated by the host's vascular . This encapsulation typically occurs within 4-6 weeks, with neointimal coverage progressing from approximately 13% at 7 days to over 95% by 100 days post-implantation, forming a stable neointima layer composed primarily of fibroblasts and endothelial cells. Studies in ovine models demonstrate that this process embeds the device into the vessel wall without inducing significant , maintaining vessel patency above 90% over extended periods up to 190 days, as confirmed by histological analysis and . The device's long-term stability within the vascular system is supported by mechanical and properties designed to harmonize with the vessel environment. A controlled radial , averaging around 3.66 , ensures consistent to the vessel wall without excessive that could lead to damage or migration, while the superelastic nitinol framework accommodates pulsatile blood flow and respiratory fluctuations. Anti-thrombotic strategies, including post-implantation dual antiplatelet therapy (aspirin and clopidogrel for the first 3 months), minimize clot formation, with incidence reported below 5% in preclinical and early clinical evaluations. Physiological interactions between the device and the vascular system are characterized by minimal disruption to normal and a subdued . The open-cell geometry preserves blood flow with velocity changes under 10%, maintaining wall above 0.4 Pa to prevent platelet aggregation and ensure venous patency, as modeled by in ovine studies. Unlike parenchymal neural implants, which often trigger pronounced , the endovascular placement limits the immune response to mild perivascular , with negligible and infiltration observed histologically. Ongoing monitoring of the device's vascular integration involves non-invasive and minimally invasive techniques to verify positioning and interface integrity. Periodic assesses vessel patency and neointimal incorporation without procedural complications, while the subcutaneous wireless telemetry unit enables real-time evaluation of electrode impedance (stabilizing at 10-50 kΩ within two weeks) and overall system performance. These methods have confirmed stable electrode-vessel contact in human trials lasting over 12 months, supporting the device's suitability for chronic implantation.

Functionality and Operation

Neural Signal Recording

The stent-electrode recording array captures electrical activity from nearby brain tissue by detecting extracellular potentials generated by neuronal firing. Positioned within a cortical , the device's electrodes record (LFPs) from neurons approximately 250–700 μm distant, as the signals propagate through the vessel wall and , undergoing yet retaining sufficient amplitude for reliable detection, typically in the range of 10–100 μV. This biophysical mechanism leverages the conductive properties of brain tissue and , enabling the array to sense volume-conducted fields without direct cortical penetration. In terms of , a single array covers a cortical surface area of approximately 100–300 mm² adjacent to the implantation site, with inter-electrode spacing of 2–6 mm facilitating the isolation of activity from localized neural populations. This configuration supports the detection of movement-related potentials in regions, achieving decoding accuracies exceeding 90% for simple binary tasks such as intent to move versus rest. For chronic performance, the array demonstrates long-term stability, with signal amplitudes exhibiting minimal drift over implantation periods up to 190 days in preclinical ovine models and up to 12 months in trials. Ovine studies, for example, have confirmed consistent recording of beta-band oscillations (13–30 Hz) associated with motor planning, maintaining signal-to-noise ratios comparable to surface arrays throughout the duration. Recent studies as of 2025 have also demonstrated modulation in gamma bands (30–150 Hz) for motor activity, with signal-to-noise ratios of approximately 1.7–6.8 dB. Key noise sources in these recordings include artifacts from vascular pulsations, which introduce low-frequency interference around 1–2 Hz. These are effectively mitigated using common-mode rejection, where differential amplification between electrode pairs cancels out shared environmental noise while preserving neural signals.

Signal Processing and Transmission

The signal processing pipeline in the stent-electrode recording array, commonly known as the Stentrode, commences within the implantable receiver-transmitter unit (IRTU), which houses an integrated application-specific integrated circuit (ASIC) for initial handling of captured neural signals. Low-noise amplifiers (LNAs) with a noise floor below 2.5 µV_rms amplify the faint 10–100 µV electrocorticographic (ECoG)-like signals in the 1–300 Hz frequency band (encompassing mu, beta, and low-gamma rhythms), utilizing chopper stabilization techniques and high common-mode rejection ratios exceeding 100 dB to minimize artifacts while maintaining input impedance above 1 GΩ. A programmable gain amplifier (PGA) follows to adjust amplification levels, typically ranging from 1,000 to 10,000 V/V, accommodating variability in signal amplitude across channels. These amplified signals undergo multiplexing to manage multiple electrode inputs efficiently, followed by analog-to-digital conversion via a 12–16 bit ADC sampling at 1 kHz per channel, incorporating anti-aliasing low-pass filters with a cutoff around 400 Hz to ensure faithful digitization without aliasing. Wireless transmission of the digitized data occurs from the IRTU to an external telemetry unit (ETU) positioned on the chest, leveraging (BLE) protocol for low-latency, secure bidirectional communication at data rates up to 1 Mbps, supported by to maintain integrity over distances of 5–10 cm. On-device compression techniques, such as delta or , reduce data volume prior to transmission, enabling real-time relay without excessive bandwidth demands. Power for the IRTU is delivered battery-free through an link operating at a resonant of 6.78 MHz, connecting to an external charger and maintaining a total power consumption under 10 mW via duty-cycling and low-leakage processes. Real-time algorithms embedded in the processing chain include threshold-crossing methods for detecting neural events amid background activity, as well as adaptive filtering to suppress physiological artifacts like cardiac pulsations and respiratory influences. Feature extraction focuses on spectral power in relevant bands (e.g., beta oscillations at 13–30 Hz) to distill actionable neural features for brain-machine interface (BMI) applications, with downstream integration of techniques like Kalman filtering providing a brief probabilistic framework for estimating intended movements, such as cursor control trajectories from noisy signal ensembles. Furthermore, the system integrates with generative AI software that processes neural signals to generate text or audio outputs, enhancing communication for users with severe disabilities. In 2024, Synchron incorporated OpenAI’s GPT model to enable automated prompts for texting and chatting based on neural inputs, including emotional context. This was followed by a 2025 collaboration with Nvidia, utilizing the Holoscan platform for real-time neural decoding and the development of Chiral™, a cognitive AI foundation model trained on deidentified neural data to support advanced intent translation and multimodal outputs. To ensure long-term reliability in the physiological environment, the electronics are protected by hermetic encapsulation using laser-welded housings with feedthroughs, which resist corrosion and support device lifetimes exceeding five years based on accelerated aging tests.

Applications

Brain-Machine Interfaces

The stent-electrode recording array integrates with brain-machine interfaces by capturing high-fidelity neural signals from the via endovascular placement in the , enabling the decoding of intended movements to control external devices such as computers and prosthetic limbs. In human trials involving patients with severe , decoding algorithms have achieved classification accuracies of 70.37% to 91.43% for distinguishing multiple attempted movements (e.g., hand or ankle actions) from rest states, using features like gamma and high-gamma band activity. These signals are processed in real-time to translate motor intentions into digital commands, supporting applications in restoring communication and mobility for individuals with neurological impairments. Preclinical studies in sheep from 2021 demonstrated the device's capability for stable, chronic neural recording over extended periods, facilitating thought-controlled digital interactions such as cursor control and switch toggling, which achieved effective typing rates of up to 20 characters per minute in analogous setups. In human applications, the array targets conditions like (ALS) and stroke-related paralysis, where implantation in the vasculature allows patients to regain control over digital interfaces for communication and task execution, with clinical trials enrolling individuals with impairment from these etiologies. For instance, ALS patients in early feasibility studies used the system to perform text-based interactions at mean speeds of 16.6 correct characters per minute with 93.9% selection accuracy. This capability is further enhanced by integration with generative AI technologies, such as OpenAI's GPT for thought-to-text and thought-to-audio generation, enabling more natural and efficient communication for non-verbal paralyzed patients by producing automated prompts aligned with contextual inputs like emotional states. Additionally, through a partnership with Nvidia, the Chiral brain foundation model is being developed, trained on neural data to abstract human cognition and improve decoding for motor control and other intentions in paralyzed individuals. As of 2024, the U.S. COMMAND trial reported successful deployment in all six enrolled patients with severe paralysis, enabling signal recording for BMI applications. The array supports closed-loop BMI systems by leveraging recorded neural signals for adaptive learning algorithms that refine decoding performance through iterative feedback, while the implanted transmitter enables wireless output to peripherals like tablets or robotic arms for seamless device interaction. This closed-loop architecture allows real-time adjustments to user-specific neural patterns, enhancing control precision over time. For quadriplegic patients, the technology provides significant benefits by enabling independent performance of daily tasks—such as emailing, , , and texting—solely through thought, thereby reducing reliance on caregivers and improving without requiring physical movement. In one , all implanted participants successfully completed routine digital activities using the BMI, with no device-related impediments to autonomy.

Clinical Monitoring in Neurology

Endovascular neural interfaces, including designs like the Stentrode, have potential for real-time monitoring of activity in conditions such as by recording from cerebral veins to capture electrocorticography-like signals without open- . Studies with endovascular electrodes have shown signal amplitudes 2–5 times higher than scalp (EEG), offering sensitivity comparable to traditional grids. Such devices may also support monitoring of cerebral ischemia during interventions or tumor resections by tracking neural activity changes indicative of vascular compromise, and serve as chronic alternatives to scalp EEG for patients with neurological conditions. These proposed applications emphasize passive diagnostic monitoring, distinct from therapeutic stimulation. Diagnostic advantages include superior spatiotemporal resolution at the millimeter scale, exceeding scalp EEG limitations in detecting deep or focal activity. Post-implantation, they could facilitate ambulatory monitoring for long-term neural data assessment.

Advantages and Limitations

Minimally Invasive Benefits

The stent-electrode recording array, commonly known as the Stentrode, offers substantial procedural advantages over traditional open-brain surgical methods like for neural implants, primarily due to its endovascular deployment via the . This approach eliminates the need for skull penetration or direct brain tissue manipulation, thereby avoiding risks associated with open surgery such as hemorrhage, , and direct neural trauma. In clinical evaluations, the Stentrode has demonstrated a low complication rate of less than 2%, contrasting with infection rates of 3-9% reported for procedures involving . Furthermore, the absence of brain tissue disruption contributes to markedly shortened recovery periods, with patients typically discharged from the hospital within a few days post-implantation, compared to weeks of hospitalization and rehabilitation often required after invasive surgeries. This minimally invasive nature enhances accessibility for patient populations previously deemed high-risk for open procedures, including the elderly, those with coagulopathies, or individuals with comorbidities that contraindicate and prolonged recovery. The procedure can often be performed under with fluoroscopic guidance, with endovascular deployment lasting approximately 90-120 minutes and total procedure time averaging 232 minutes in early trials, potentially enabling outpatient or short-stay settings in future implementations. By leveraging the vascular system for deployment and integration, the Stentrode broadens eligibility for brain-machine interfaces in progressive neurological conditions, allowing earlier intervention without the barriers posed by surgical invasiveness. In terms of scalability, the endovascular route facilitates the potential deployment of multiple electrode arrays through a single venous access point, targeting various cortical regions while minimizing procedural complexity and vascular trauma. The Stentrode's design has comparable costs to traditional systems, estimated at $50,000 to $100,000 per implantation as of 2024. These factors contribute to improved quality-of-life outcomes by preserving cosmesis—avoiding visible scars or burr holes—and maintaining cognitive function through non-disruptive placement, thus supporting sustained independence and reduced psychological burden from invasive interventions.

Technical and Biological Challenges

The stent-electrode recording array, commonly known as the Stentrode, faces several technical challenges that impact its performance compared to traditional invasive neural interfaces. Recent clinical trials report no electrode dropouts, with all 16 channels remaining functional up to 12 months post-implantation. The device's channel count is limited to 16 , significantly lower than the 100 or more channels available in penetrating arrays like the Utah electrode array, which restricts spatial resolution and the ability to capture fine-grained neural population activity. Wireless transmission from the subcutaneous receiver can also be susceptible to interference, particularly in deep brain placements, potentially degrading signal fidelity during chronic use. Biological risks associated with the Stentrode primarily stem from its interaction with the vascular environment. remains a concern, necessitating dual antiplatelet therapy for at least three months post-implantation to mitigate clot formation, with general endovascular stent literature reporting incidences of 1-3% despite such precautions; however, no has been observed in Stentrode trials to date. Endothelial , or neointimal proliferation, can lead to vessel lumen narrowing, as evidenced by reductions from 5.48 mm² to 4.06 mm² in preclinical ovine models, though without resulting in occlusion in reported cases. Device migration is minimal, with mean changes of 0.45 mm over 12 months in human trials, but long-term or tissue encapsulation may contribute to gradual signal degradation beyond current follow-up periods, although data as of 2024 show stability up to 12 months without significant attenuation through the vessel wall. Scalability barriers further hinder widespread adoption of the Stentrode. Customization is required to accommodate vascular , complicating standardized and deployment in diverse patient populations. Regulatory challenges arise when extending functionality to include capabilities, as current approvals focus on recording, with limited long-term (typically 12 months) impeding broader clinical validation. As of 2025, the COMMAND has confirmed in 6 additional patients with no device-related serious adverse events over 12 months, contributing to a total of 10 implants demonstrating stable performance. Efforts to address these challenges include advanced coatings to enhance and reduce risk, as demonstrated in preclinical stability improvements. AI-based denoising algorithms have been applied for real-time to compensate for and dropouts, improving overall usability. However, achieving high-density recording comparable to invasive systems remains unresolved, with ongoing needs for miniaturized designs to minimize interference and support scalability.

Clinical Studies and Evidence

Preclinical and Animal Studies

Preclinical investigations of the stent-electrode recording array, commonly referred to as the Stentrode, have focused on validating its , , and neural recording capabilities in animal models prior to clinical . These studies emphasized minimally invasive endovascular deployment to minimize tissue damage while ensuring long-term functionality within cerebral vasculature. Large animal models, particularly ovine, were prioritized due to their vascular anatomy's similarity to humans, allowing for reliable assessment of device integration and signal quality. All experiments were conducted under Institutional Animal Care and Use Committee (IACUC) approval to adhere to ethical standards for . A pivotal 2016 study implanted the Stentrode in five freely moving sheep (n=5), demonstrating stable chronic recordings of activity for up to 190 days post-implantation. The device captured high-fidelity neural signals comparable to traditional epidural arrays, with an effective bandwidth of approximately 193 Hz and signal-to-noise ratios suitable for decoding. Notably, the array's signal quality supported its potential for brain-machine interface applications. Vessel patency was maintained throughout, with no instances of or occlusion observed via and . Early assessments confirmed the device's compatibility with vascular , showing no vessel occlusion and rapid neointimal coverage without significant inflammatory disruption. In ovine models, long-term signal stability exceeded six months, with impedance values stabilizing at around 2.28 kΩ at 1 kHz, indicative of effective -tissue integration. functionality retention reached 98% across channels, supporting chronic use. Histological analyses revealed minimal , with negligible infiltration of CD68-positive macrophages and lymphocytes, typically less than 5% of the perivascular area, underscoring the device's low . These findings collectively established the Stentrode's safety profile for extended implantation.

Human Trials and Outcomes

The first-in-human implantation of the stent-electrode recording array, known as the Stentrode, occurred in 2019 in as part of the SWITCH (Stentrode with Thought-Controlled Digital Switch) early feasibility study. This trial enrolled five participants with severe bilateral upper-limb due to (ALS) or primary lateral sclerosis, with four analyzed after one withdrawal. The endovascular procedure successfully deployed the device in the adjacent to the in all cases, enabling chronic neural recording without open-brain surgery. Safety outcomes from the SWITCH trial demonstrated no device-related serious adverse events, including no instances of vessel occlusion, device migration, , or permanent over 12 months of follow-up. Mild adverse effects, such as procedural bruising or transient headaches, occurred in eight instances but resolved without intervention. Signal stability was maintained throughout, with a mean bandwidth of 233 Hz (standard deviation range across sessions: 7-32 Hz), supporting reliable neural recording comparable to invasive arrays. Efficacy for brain-machine interface (BMI) applications included hands-free control of digital devices, such as texting and , with one participant achieving 93.9% selection accuracy and 16.6 correct characters per minute using thought-derived cursor control. In 2022, the COMMAND trial commenced in the United States as an early evaluating the Stentrode in six participants with severe chronic bilateral upper-limb paralysis unresponsive to other therapies, including cases of . Deployment was successful in 100% of cases, with a median procedure time of 20 minutes and precise coverage. Over 12 months, no neurologic or vascular serious adverse events occurred, and signals reliably translated into digital motor outputs for tasks like device navigation. Signal performance remained stable, with no evidence of degradation, facilitating consistent BMI functionality. As of August 2025, a participant demonstrated native thought-control of an Apple , and in November 2025, Synchron secured $200 million in funding to support pivotal trials and commercialization. Across both trials, the absence of major adverse events underscores a favorable safety profile, with stroke risk below 1% and zero explantations reported. By , 10 implants had been performed in human participants, primarily in Phase I/II studies focused on and BMI applications, with ongoing efforts toward pivotal trials. These outcomes highlight the device's potential for long-term, minimally invasive neural interfacing, building on preclinical evidence of signal fidelity.

Future Directions

Ongoing Research Initiatives

Synchron is leading ongoing clinical trials with its COMMAND study, a multi-year effort spanning 2023 to 2027 across sites in the United States, aimed at evaluating the Stentrode in up to 50 patients with (ALS) to assess safety, , and efficacy in restoring digital device control through neural signals. In September 2024, Synchron announced positive results from the COMMAND early , confirming the safety of the Stentrode brain-computer interface (BCI) with no neurologic safety events in six patients and successful targeting. As of August 2025, the device enabled the first thought-controlled experience using Apple's BCI protocol. Key collaborations are advancing the technology's clinical translation, including a partnership with NVIDIA announced in January 2025 to integrate the Holoscan platform for real-time signal processing and AI enhancements in BCI technology. Efforts focus on integrating artificial intelligence algorithms for real-time signal enhancement, including noise reduction and decoding optimization to improve intent recognition accuracy in diverse patient populations. In March 2025, Synchron unveiled Chiral™, the world's first cognitive AI brain foundation model, developed in collaboration with NVIDIA. Chiral is trained on large-scale neural data collected from Stentrode implants using generative pre-training techniques, enabling advanced features such as higher-dimensional intent translation, real-time neural decoding with minimal latency, and thought-controlled interactions with digital and physical environments, including control of devices like the Apple Vision Pro. In November 2025, Synchron raised $200 million in Series D to advance of the Stentrode BCI platform and expand AI and engineering operations. The same month, the Australian government invested A$54 million in Synchron through the National Reconstruction Fund to support further development. Current research emphasizes technical refinements such as improving spatial resolution of neural recordings without additional invasiveness. Endovascular brain-computer interfaces like the Stentrode show potential for post-stroke applications in restoring function for patients with paralysis.

Potential Technological Advancements

Future developments in stent-electrode recording arrays, commonly known as Stentrodes, are poised to enhance neural resolution through advancements in microfabrication techniques that enable high-density electrode configurations exceeding 64 channels. Current Stentrode designs typically feature 16 platinum-iridium electrodes on a nitinol scaffold, but emerging prototypes incorporate flexible polyimide substrates to support hundreds of electrodes via active multiplexing, allowing for finer spatial mapping of cortical activity without increasing device size. These high-density arrays could integrate optical elements, such as optrodes, combining electrical recording with optogenetic stimulation to target specific neuronal populations with greater precision, as demonstrated in related flexible, foldable neural interfaces. Integration of stimulation capabilities represents a key advancement, transforming Stentrodes into bidirectional brain-machine interfaces (BMIs) suitable for closed-loop (DBS) in conditions like . Preclinical studies have shown that endovascular Stentrode electrodes can evoke cortical activation, eliciting movements in facial and limb regions, with computational models indicating efficacy comparable to traditional DBS leads for targeting subcortical structures near accessible vessels. Adaptive, real-time using feedback from recorded neural signals may minimize side effects while maintaining therapeutic efficacy in neurological disorders. Advancements in and are expected to address signal quality and long-term biocompatibility. Machine learning algorithms, such as those employed in current Stentrode systems, decode motor intent from high-gamma band activity with high fidelity, and future iterations could incorporate for automated artifact removal, improving signal-to-noise ratios in chronic recordings. Additionally, bioresorbable elements, including degradable polymers and alloys, may replace metallic scaffolds to mitigate chronic inflammation and thrombosis risks, allowing temporary neural interfacing that dissolves post-use while preserving vascular integrity. Broader applications could extend Stentrodes beyond cortical recording to spinal cord and peripheral nerve interfaces, enhancing scalability for neuromodulation in spinal injuries or neuropathies. Computational modeling supports endovascular deployment for peripheral nerve stimulation, optimizing electrode placement to activate targeted axons with minimal off-target effects. As adoption grows, ethical frameworks emphasizing equitable access and data privacy will be essential to guide widespread clinical translation.

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