Synchron’s nonsurgically implanted BCI could offer new hope for paraplegics

It was an early-career tragedy that inspired Australian neurologist Tom Oxley to work on a new kind of brain-computer interface.

When Oxley was beginning his neurology training, he worked with a patient who was so diminished by a stroke that he couldn’t move anything but his eyes. The man—only 40, and the CEO of a company—made it clear that he didn’t want to live in his current “locked-in” condition. He wanted to die. So the doctors obliged him, doing nothing to fight off the stroke. They made him comfortable.

“This was a guy whose brain was working normally, except that he couldn’t move the muscles,” Oxley says. “I had this profound moment of realizing the limitation of the human body when it comes to the disconnect between what our brains can do and the way we express ourselves.” We express ourselves almost exclusively with our muscles. When we lose control of them we simply can’t communicate. 

That realization never left Oxley, and it led to his interest in BCIs. In 2012 he started his own BCI company, Synchron, which has since raised $70 million from Khosla Ventures and others, with some support from the U.S. and Australian governments.

Synchron, which is head quartered in Brooklyn, is one of a growing number of companies working on brain-computer interface (BCI) technology, which may one day allow both the disabled and mainstream consumers to control computers with their thoughts. Some BCI tech reads brain waves from outside the body, such as with a sensor-laden headband (Snap’s NextMind tech) or a bracelet (Meta’s CTRL-Labs). Others, such as Elon Musk’s Neuralink, must be surgically implanted in the brain. Various BCIs strike different balances between non-invasiveness and accuracy: A BCI bracelet, for example, is far easier to install than Neuralink but also must interpret brain signals through a layer of skin, and farther away from the brain.

Synchron is notable for striking a new kind of balance. Instead of introducing a BCI by drilling a hole in somebody’s skull, or strapping a device onto a limb, the company uses a stent that’s delivered to just the right blood vessel in the brain at the end of a catheter. (Stents are already commonly used to deliver medication or clear blood clocks for stroke victims.)

The approach, so far, has been warmly received by regulators. Synchron recently announced the selection of the first patient in its U.S. trial, which the Food and Drug Administration (FDA) approved in 2020. It’s taking place at Mount Sinai Hospital in New York. The company first tested the technology with live patients in Australia, in part as a way of gathering the research data needed to convince the FDA to approve a U.S. trial.

Synchron’s stent, which is branded as “stentrode,” looks like a small (8mm in diameter) tube of wire mesh (it’s made of nitinol), Oxley says. It can be implanted in a procedure performed in a regular hospital cath lab, in which the small device is introduced into the jugular vein in the neck and then fed up into a blood vessel called the Superior Sagittal Sinus in the brain.

Oxley describes the BCI as a kind of “scaffolding” that lines the wall of the blood vessel, and eventually grows into the tissue there. The nitinol mesh can be tuned to receive messages coming out of the brain that, in normally functioning people, would control movements of limbs and fingers.

“There is a very well-characterized part of the brain that controls all the muscles in your body called the motor cortex,” Oxley says. “It’s the command center of the brain for movement.” Oxley, a neurosurgeon, says the location and function of the motor cortex is known science and nothing new, and it’s pretty much the same in every person.

“To make double-sure, we put patients through an MRI scanner and we make that part of the brain light up by having them try to move [various body parts]”, Oxley adds.

When the stent is in just the right place, it begins to relay information about the patient’s neural impulses via Bluetooth to a small device outside the body. And that device is where the impulses are translated into the zeros and ones that a computer can understand. So, even though a patient may not be able to actually move a mouse physically, they can, in essence, control one with their mind.

This opens up some life-changing possibilities for victims of paralysis whose sole mode of communication is movements of their eyes. The four Australian patients who have already been implanted with the stent were able to do things like email, text, and even shop for groceries.

On the other hand, there are risks. The patient may have unrealistic expectations about how much function can be restored by the BCI. Different patients will show different levels of compatibility with the BCI. In a 2014 research paper, University of Calgary neuroethicist Walter Glannon wrote that, on a purely clinical level, there’s a risk that a BCI could “cause adverse changes in the surrounding tissue and result in neurological and psychological sequelae (related conditions).”

Today, Synchron is totally focused on helping paraplegics, but it’s worth remembering that some of the most useful consumer technologies of today–such as speech-to-text and text-to-speech–were originally developed to enable the disabled. Technologies that are just now becoming mainstream–such as eye-tracking sensors in AR/VR glasses–started out as accessibility tech. So it’s fair to think about what a brain-computer interface that can be installed at an outpatient cath lab might mean for personal computing in the future.

Oxley doesn’t shy away from the topic. Researchers, he says, may come to understand how to seat BCIs in other brain centers than the motor cortex. They may be able to communicate intentions from the brain other than the movement of body parts.

“I think beyond that there will be many new replications and realms–emotion and geolocation and memory,” Oxley says. “From now until eternity the ability to get zeros and ones out of the brain will go up–theoretically up to the absolute maximum number of cells that are in the brain.” Computers, in other words, may become able to understand our finer, more nuanced intentions.

“But that’s a long way away, and there is going to be a long period of incredible innovation that’s going to help many people who are separated by paralysis.”