The Synchron brain-computer interface system relays signals from the brain to a device in the chest, then translates 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 to tap into blood vessels to pick up signals from the brain.
They say they’ve already enabled a small group of paralyzed ALS patients to control a computer with their minds, and hope there will be more applications for their technology.
Shortly after the New York-based company released new results from a safety study for its implant, Synchron Neuroscience Director Peter Yoo spoke with Medical design and outsourcing about the Stentrode implant and how catheter delivery could make BCI technology simpler, safer and more accessible than the main alternative: open-brain surgery.
Peter Yoo is Director of Neuroscience at Synchron [Photo courtesy of Synchron]
“The new approach to catheter delivery increases the number of doctors who can deliver our devices compared to a very specialized type of surgery,” Yoo said in an interview. “The techniques we use are standard angiography procedures and other neuro-interventional techniques performed by stroke specialists. We hope this will contribute to the proliferation of technology and access to technology, that it can be cheaper and more available to patients who need it.
This conversation has been edited for more space and clarity.
MDO: How did BCI technology get to where it is today?
Yo: BCI has come a long way. It’s been in the works for a few decades now, but it hasn’t quite translated into the real-world patient context yet. It’s largely an engineering problem because people have to pave the way to get into the brain or inside the skull to record these high-fidelity signals. … The other side of the technology, the user experience and user interface and the software and marketing side of the product, has been extensively worked on recently. It moves quite quickly now, this space. The initial focus was largely on trying to regain 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 make an impact in patients’ homes. So that’s what Synchron is really focusing on, not just an engineering challenge, but also a commercial product challenge, trying to make a BCI that’s actually usable at home without needing a PhD. neuroscientist to set it all up.
MDO: Did Synchron focus from the start on the administration of catheters?
Yo: Neurointervention is a relatively newer field, but it is now an established field where people routinely enter the brain through the vasculature without the need to perform craniotomy or open brain surgery. [for] intracranial stenting to treat certain conditions, for clot retrieval, coiling and that sort of thing. Very similar to the heart space, which is how we always started. It was about solving mechanical problems, but then they quickly moved on to cardiac EP (electrophysiology), putting electronics and devices on top of those mechanical devices. So that’s the path that seemed obvious to us, obvious to Tom (co-founder and CEO, Dr. Thomas Oxley), because he was a neurologist working in the field of stroke. We decided to mount the electronics on the stents which give us natural access to the brain without having to open the skull. Incidentally, the human brain and many other mammals have this natural venous pathway that goes into the brain. … We are exploring these pathways to enter the brain using standard techniques performed routinely by angiography.
The Synchron Stentrode brain implant expands inside a blood vessel, placing its electrodes against the vessel wall to detect brain signals. [Image courtesy of Synchron]
MDO: Were there any obstacles to inserting a catheter?
Yo: The main challenge was that there was essentially a lack of chronic data on leaving a device inside the blood vessel permanently. There is now a routine case: the treatment of idiopathic intracranial hypertension [where] for some unknown reason, intracranial pressure builds up. People have stented the transverse sinus – which is the sinus that runs along the back of the head to the side – permanently placing stents there with a major complication rate of less than 2%. But these are the only data available on chronic stents inside the brain. So we had to do a lot of back-end work, bench testing and large animal testing to make sure that leaving a permanent device with the lead inside the blood vessel doesn’t cause thrombosis or other health risks.
MDO: Why does it have to be permanent?
Yo: The stent is embedded in the brain and it helps with several things. This improves the insulation of the electrodes so that they do not come into contact with blood and other conductive elements. The electrodes inside the blood vessel hold the device in position and improve our ability to register the signal, which increases stability and fidelity. … We are looking for the device retirement security profile … but currently it is a permanent device.
MDO: What were the big engineering challenges your team had to overcome?
Yo: Full disclosure: Hardware manufacturing and design is not my particular area of expertise. But we had to create many processes from scratch. Mounting electronics on stents that will be permanently implanted did not exist before us. We started making them manually, now we print them. All of these processes and methods had to be created from scratch, drawing on many other manufacturing practices and know-how. And we had to solve the problem of once you made these recording heads, the sensors, how can we connect them to blood vessels and connect them to certain transmission units. All of these transition zones and the creation of electronics to wirelessly transmit data out of the body was also a problem and a challenge. The tortuosity of the blood vessels means that the device had to be flexible, but firm enough to be able to push the device into the brain through these tortuosities. Getting those good spots was definitely a challenge for our mechanics team.
MDO: How is this device implanted?
Yo: We do a direct puncture of the internal jugular vein (IJV)—we don’t make an incision—to access the blood vessel. From this point, for most individuals, there is a path through the IJV that starts from the sigmoid – which is this rounded, coiled piece – into the transverse sinus and then into our target vessel, which is the superior central sinus . This beautiful pathway runs from the IJV to the location of the target blood vessel at the top of the brain. Once you deliver the device through a series of catheters and unsheath all the catheters, you have the device wire sticking out of the IJV. From this point we perform a standard tunneling procedure – which is often performed in the cardiac EP space for implantable pulse generators – to tunnel the lead under the skin into a small breast pocket and place the unit telemetry inside the chest pocket. Basically, the wire goes under the skin, comes out of a pocket, you plug it in. Then we put the rest in the chest pocket. Everything is completely inside the body. This is obviously very good for infection control. Some of the other devices have transdermal connections, which means they are not fully implanted. With our device, we’ve really done careful designs to make sure the implants are fully implanted and the data transmission is wireless because we reach the brain and we’re very proactive in infection control.
The Synchron BCI system relays data from the brain to a transmitter in the chest which wirelessly transmits the data to another device outside the patient. [Image courtesy of Synchron]
MDO: What about wireless data connecting to a smartphone or a computer?
Yo: Our current iteration of the device transmits raw implant data via an RF link. Because it’s a custom communications protocol it goes into a little middle box so we can sample the signal and then it goes straight into a commercial laptop where it was running our algorithms so we could translate incoming signals to outputs so that the patient can use generic, consumer-grade software and hardware at home without the need for a large box or specialized equipment.
MDO: How else could this technology be used?
Yo: Basically, we are trying 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 are doing now, or it can be used to acutely diagnose certain conditions like epilepsy . …Furthermore, we can feed information back into the brain – that’s stimulation, we’ve published previous work on this – which means we can provide stimulation therapy to the brain as this field has been doing for a long time with deep brain stimulation. This can potentially treat a variety of conditions.
MDO: What are these conditions?
Yo: All the blood vessels that proliferate throughout the brain, theoretically we can get to these places, given that they are not too small. There will be a lower limit of tiny venules or tiny arteries that would be difficult to reach with current technology, but there are many, many, many millions of small vessels that you could potentially reach. Currently, the way deep brain stimulation reaches these areas is to perform a craniotomy and insert a rod there. Obviously, this comes with its own risks, but when targeted correctly and you stimulate specific parts of deep brain areas that have been studied for decades. , you can cause very good symptom relief effects. We would do the exact same thing, except we would reach those areas through the blood vessels and stimulate from inside the blood vessel, which means we don’t need to come into direct contact with the brain, which has its own set of benefits in terms of immune responses. It’s fine to 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 these smaller pathways to the brain, like miniaturizing catheters or reducing the size of electrodes?
Yo: It’s just a continuation of the ongoing work of the R&D team, to continue to miniaturize and improve access methods to get to those smaller places. It is a continuous work that is carried out at Synchron.
