Fri. Mar 24th, 2023
Behold, the stentrode.
Enlarge / Behold, the stentrode.

University of Melbourne

Australian neurologist Tom Oxley was on vacation in the US in November 2010 when he decided to do some work. So he pitched an electrode array for reading brain waves to the Defense Advanced Research Project Agency’s (DARPA) Military Prosthetics program. Rather than requiring invasive surgery to implant directly into the brain, Dr. Oxley’s electrode array can be screwed into a vein that runs through the brain.

Oxley was surprised to get an immediate response and invited him to discuss his device in person. When meeting with DARPA’s Colonel Geoffrey Ling, Oxley got an even bigger surprise. Here’s how Oxley describes the encounter:

[Col. Ling] leaned back in his chair and said, “Well, that’s interesting. No one has done that at DARPA. Why don’t you go home and get a team together and we’ll give you a million dollars to build this thing.”

Easier said than done. As a neurologist, Oxley didn’t have the technical know-how to build a complicated electronic device that could be compressed into a submillimeter catheter and still retain its signaling ability. And he didn’t know who could; he was not an academic with years of research collaborations and connections behind him. “It was surreal,” Oxley told an interviewer. “All of a sudden I was starting my PhD and had several million dollars to work with and a whole area to start my own lab.”

That turned out to be enough to spark a large-scale collaboration that eventually resulted in a device called the stentrode. In February 2016, the stentrode was announced in a paper by 39 authors Nature Biotechnology. How do you go from being a green graduate student to building both a research team and a working device in five years?

For Dr. Oxley, the process started close to home. He worked at the University of Melbourne’s Parkville Precinct, which had developed both a bionic ear and a bionic eye. The university also had a medical school, as well as the Florey Institute of Neuroscience and Mental Health, which Oxley could draw from. Before finishing, Oxley’s team had spanned continents, combining disciplines as diverse as neurology, veterinary medicine, statistics, materials science, medical imaging and electrical engineering. “I think it worked in part because I was young and open-minded,” says Oxley. “I never thought I had all the answers, but that someone smarter than me did. So I kept asking different academics until I heard what I thought was the most sensible solution.”

Bypass brain surgery

Electrodes have been used to read brain activity and control external objects – it’s no longer the stuff of science fiction. Electrodes in the brain allowed a paralyzed man to kick off the 2014 World Cup and a paralyzed man to play Guitar Hero. But the technology is not without drawbacks. For best results, surgeons must open a patient’s skull and insert an electrode array into the brain itself, a procedure associated with a 26 percent risk of infection or bleeding. The brain can also respond to the electrodes with chronic inflammation and scarring, making the patient sick and reducing the electrodes’ ability to pick up signals. The dangers increase as surgeons try to access information-rich areas deep in the brain’s cortex.

While training as a neurosurgeon, Oxley learned that stents can be inserted into blood vessels deep in the brain. He suspected that electrodes could be delivered in the same way. Stents are made of a biocompatible metal or plastic mesh formed into small pipes. These pipes are compressed and inserted into a catheter to be delivered to a part of the blood vessel that is blocked, either by a clot or collapsed walls. Once ejected from the catheter, the stent expands and pushes open the walls of the vessel, allowing blood to flow freely again. Stents are often used to correct cardiovascular problems, such as cases where cholesterol plaques have decreased blood flow.

Oxley realized that a stent with electrodes would expand to force the electrodes against the walls of the vessel, bringing them close to the brain tissue just outside. These electrodes could potentially read nerve cell activity deep in the brain without the invasive surgery currently used.

Oxley’s stentrode differs from stents currently in use. At 3 cm long, with criss-cross metal struts and laser-cut platinum discs, the stentrode looks more like a delicate piece of jewelry than the frontier of medical technology. Human trials will begin in 2017, in hopes that paralyzed volunteers can use stentrodes to control their wheelchairs or even exoskeletons. “Essentially what we’re trying to build is a bionic backbone,” Oxley told Ars.

Like this, except much more bionic and modern.
Enlarge / Like this, except much more bionic and modern.

VintageMedStock/Getty Images

Step one: paperwork

It wasn’t clear that all of that would be possible when Oxley first piqued DARPA’s interest. But his work started before he even left Washington DC when he contacted former classmate Rahul Sharma. Sharma is a cardiologist who also has business experience, so Oxley called him and said, “Rahul, DARPA are interested in funding an endovascular neural interface project. They suggested that I apply for a patent immediately. We need money.” Oxley also turned to a friend who ran an intellectual property firm in Melbourne who began work on a patent application. As the DARPA funding was not yet official, Oxley decided and Sharma to cover the legal costs themselves.

Meanwhile, Oxley’s supervisor, professor of medicine Terence O’Brien, kicked off the process of assembling a scientific team by introducing Oxley to engineers Tony Burkitt and David Grayden. Their work on the bionic ear and eye projects gave them deep knowledge of implanted devices, brain signaling and signal processing. They in turn introduced Oxley to biomedical engineer Nick Opie, also from the bionic eye team. Opie eventually became Oxley’s co-leader on the project. Together they spent the first half of 2011 developing a detailed proposal to present to DARPA to get their funding confirmed.

While waiting for the money, Oxley applied for permission to test the stentrode on animals in Australia. To do this, he turned to the ethics committee of the Florey Institute of Neuroscience and Mental Health, where he was guided by Clive May, head of the neurovascular group. May has spent a quarter of a century studying how the brain controls the cardiovascular system, and he runs a hospital-style operating room and an intensive care unit for examining the brains of large animals.

“I got involved because Tom Oxley had nowhere to do the studies, had no experience of the surgical techniques required, and no experience of using large animals,” May told Ars. Together, he and Oxley figured out how to test the still-theoretic stentrode for safety and efficacy in a living being.

By akfire1

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