Synchron’s neuroscience director explains brain implant technology and potential applications

The Synchron-brain computer interface system transmits signals from the brain to a device in the chest and then converts the signals into action on a computer. [Image courtesy of Synchron]

Officials at Synchron, the developer of the catheter-delivered Stentrode brain-computer interface (BCI) implant, believe they are the only BCI company that drills blood vessels to receive signals from the brain.

They say they have already enabled a small group of paralyzed ALS patients to control a computer with their minds, and hope there will be more applications of their technology.

Shortly after the New York-based company released new results of a safety study for its implant, Synchron Director of Neuroscience Peter Yoo spoke with Medical Design & Outsourcing about the Stentrode Implant and how catheter delivery can make BCI technology easier, safer and more accessible than the leading alternative: open brain surgery.

Peter Yoo is the director of neuroscience at Synchron [Photo courtesy of Synchron]

“The new approach to catheter delivery increases the number of physicians who can deliver our devices compared to a highly specialized form of surgery,” Yoo said in an interview. “The techniques we use are standard angiography procedures and other neuro-interventional techniques performed by stroke physicians. We hope it will help with the spread of the technology and access to the technology, that it can be cheaper and more available to the patients who need it.”

This conversation has been edited for space and clarity.

MDO: How did BCI technology get to where it is today?

yo: BCI has been on a bit of a journey. It’s been a few decades in the making now, but it hasn’t quite translated to the real-life patient environment yet. It’s largely been a technical problem, as humans have to pave the way to get into the brain or skull to pick up these high-fidelity signals. … On the other side of the technology, the user experience and UI and the software and the commercialization of the product, much of the work has been done recently. It’s going pretty fast now, this space. The initial focus was largely on regaining physical mobility — exoskeletal controls and robotic limbs — but most of the space has shifted to controlling digital devices. Smart devices are essentially ubiquitous. We are trying to capture all of these timely aspects to create our first commercial BCI product that can have an impact in patients’ homes. So that’s what Synchron really focuses on, not just a technical challenge, but a commercial product challenge, trying to make a BCI that is really usable at home without a Ph.D. neuroscientist to set everything up.

MDO: Was Synchron focused on catheter delivery from the start?

yo: Neurointervention is a relatively newer field, but it is now an established field where people routinely move through the vasculature to the brain without having to perform a craniotomy or open brain surgery [for] intracranial stenting to treat some conditions, for blood clot retrieval, coiling and things like that. Very similar to the heart space, that’s how we always started. It was solving mechanical problems, but then they quickly moved on to cardiac EP (electrophysiology), where electronics and devices were placed on top of those mechanical devices. So that’s the route that seemed clear to us, clear to Tom (co-founder and CEO Dr. Thomas Oxley), because he was a neurologist working in the stroke room. We decided to mount electronics on the stents that give us natural access to the brain without having to open the skull. Coincidentally, the human brain and many other mammals have this natural venous pathway that goes to the brain. … We’re investigating those pathways to get into the brain using standard, routinely performed techniques through angiography.

The Synchron Stentrode Brain Implant

The Synchron Stentrode Brain Implant expands in a blood vessel and places the electrodes against the vessel wall to detect brain signals. [Image courtesy of Synchron]

MDO: Were there any obstacles in placing a catheter?

yo: The biggest challenge was that there was essentially a lack of chronic data about leaving a device permanently in the blood vessel. There is now one routine case: treatment of intracranial idiopathic hypertension [where] for some unknown reason, intracranial pressure builds up. People have placed a stent in the transverse sinus — the sinus that runs sideways down the back of the head — and put stents there permanently with less than 2% of serious complications. But those are the only chronic brain stenting data available. So we had to do a lot of background work, bench-top testing and some large animal testing to make sure leaving a permanent device with the lead in the blood vessel doesn’t cause thrombosis or other health risks.

MDO: Why does it have to be permanent?

yo: The stent is taken up into the brain and that helps with a few things. This improves the insulation of the electrodes so that they do not come into contact with the blood and other conductive matters. The electrodes in the blood vessel hold the device in place and improve our ability to pick up the signal, increasing stability and reliability. … We are investigating the security profile of removing the device … but currently it is a permanent device.

MDO: What were the major technical challenges your team had to overcome?

yo: Full disclosure: manufacturing and hardware design is not my specific area of ​​expertise. But we had to create many of the processes from scratch. Mounting electronics on stents that are permanently implanted did not exist before us. We started making them manually, now we are printing them. All those processes and methods had to be created from scratch, building on a lot of different production practices and know-how. And we had to solve the problem: once you make those recording heads, the sensors, how do we connect them to blood vessels and connect them to some transmitting units. All those transition zones and coming up with electronics to wirelessly transmit the data out of the body was also a problem and a challenge. The tortuosity of the blood vessels means the device had to be flexible, yet sturdy enough that you can push the device through those twists in the brain. It was definitely a challenge for our mechanical team to get those good spots right.

MDO: How is this device implanted?

yo: We’re doing a direct puncture of the internal jugular vein (IJV) — we’re not doing an incision — to access the blood vessel. From that point on, for most people, there’s a path through the IJV that goes from the sigmoid — that’s this tortuous, round piece — to the transverse sinus and then to our target vessel, the superior central sinus. This beautiful path goes all the way from the IJV to the target blood vessel location at the top of the brain. After you have delivered the device through a series of catheters and disconnected all catheters, the device wire extends out of the IJV. From then on, we perform a standard tunneling procedure—often performed in the cardiac EP room for implantable pulse generators—to tunnel the lead under the skin into a small breast pocket and place the telemetry unit in the breast pocket. Essentially, the wire goes under the skin, comes out of a bag, we plug it in. Then we put the rest in the breast pocket. Everything is completely in the body. That is of course very good for infection control. Some of the other devices have transcutaneous connections, meaning it’s not fully implanted. With our device, we’ve made really careful designs to make sure the implants are fully implanted and the data transfer is wireless because we go to the brain and we’re very proactive about controlling infections.

Synchron BCI System

The Synchron BCI system transmits data from the brain to a transmitter in the chest that wirelessly transmits the data to another device outside the patient. [Image courtesy of Synchron]

MDO: And then connecting that wireless data to a smartphone or a computer?

yo: Our current version of the device transmits the raw data from the implantable over an RF link. Because it’s a custom communications protocol, it goes into a little intermediate box so we can sample the signal, and then that goes straight to a commercial laptop that ran our algorithms on, so we can translate the incoming signals into digital outputs for the patient to use. generic, consumer software and hardware at home without the need for a bulky box or specialized equipment.

MDO: How else can this technology be used?

yo: Essentially we try to feel. We start with brain-computer interfaces as an application, we listen to the brain and that can be used to control digital devices like we do now, or it can be used to acutely diagnose certain conditions like epilepsy. … We can also send information back to the brain – that’s stimulation, we’ve published work on that before – which means we can provide therapy through stimulation of the brain, as this field has long done with deep brain stimulation. That can potentially treat a variety of conditions.

MDO: What are those conditions?

yo: All the blood vessels that spread through the brain, theoretically we can get to those places, since they’re not too small. There will be a lower bound of small venules or small arteries that are difficult to reach with current technology, but there are many, many, many millions of tiny blood vessels that you could potentially reach. Currently, the way deep brain stimulation reaches those areas is by performing a craniotomy and inserting a rod. That comes with its own risks, of course, but if you target it the right way and you stimulate specific parts of the deep brain regions that have been studied for decades, you can have really good symptom-relief effects. We would do the exact same thing, except we reach those areas through the blood vessels and stimulate from within the blood vessel, meaning we don’t have to interact directly with the brain, which has its own set of benefits in terms of immune responses. It’s nice to just leave the brain alone and talk to it and talk to it from a distance.

MDO: Are there any technological advances you’re looking for that will open up some of those smaller pathways to the brain, like miniaturizing catheters or downsizing the electrodes?

yo: That’s just the continuous, ongoing work of the R&D team, to continue to narrow and improve the access methods to reach those smaller places. That is ongoing work that is done at Synchron.

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