Revolutionary brain-computer interface offers hope to paralyzed patients

In recent years, experimental brain-computer interface (BCI) technology has made progress toward giving severely paralyzed patients hand-free control of computers by using only their thoughts. And now for the first time in the U.S., a patient who suffers from ALS has successfully received a permanent endovascular BCI implant as part of a landmark study. 

Australian-based startup Synchron was given the greenlight last year by the U.S. Food and Drug Administration (FDA) to conduct an early feasibility study of its flagship BCI product, the Stentrode, to assess the safety and efficacy of the device in six ALS patients with severe paralysis, meaning no functional use of muscles in their arms or their legs. The trial is being conducted with support from the National Institutes of Health (NIH) Neural Interfaces Program.

Earlier this month, doctors at Mount Sinai West in New York successfully pulled off the procedure and said the patient was able to go home just 48 hours after surgery. The goal is to ensure the device can be safely implemented, as well as to see if patients can carry out simple functions such as point and click with a computer using only their brain signals. 

There have been several iterations of BCIs that have enabled study participants in the U.S. and abroad who lost the use of their limbs due to strokes, accidents or diseases such as multiple sclerosis, to control a mouse cursor, keyboard, mobile device and even a robotic arm that provides sensory feedback to the patient. 

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But the typical brain-computer interface process is invasive. It requires opening the skull and embedding an implant directly into the brain, a complicated new surgery foreign to most neurosurgeons that comes with its fair share of risks. 

But Synchron’s procedure is unique in the field of BCI. The Stentrode is an endovascular stent that enters the body through the jugular vein and snakes through an area called the transverse sinus into a secondary area known as the superior sagittal sinus — a large vein that travels snugly between the two hemispheres of the brain. The stent is inserted about halfway between the back and front of the head near the primary motor cortex, the target of the stent and the area of the brain responsible for voluntary movement. 

Once in the proper place, the stent opens up like a flower and will heal into the walls of the blood vessels over several weeks. The electrodes embedded in the stent can then record brain activity from the motor cortex. A small wire coming from the stent then takes the brain activity to a pacemaker-like unit that sits in the chest that relays signals to an external monitoring unit via Bluetooth, which is plugged into a computer. 

Months of training then take place using algorithms to decode brain signals into practical functions on a computer, such as clicking a mouse. 

“These individuals can’t initiate movements with their own muscles, but when they try to, say, move their ankle up and down, the stent can identify that signal. And because the stent is connected to a computer, it can take that signal and use it for something else, say, a left mouse click,” David Putrino, director of rehabilitation innovation for the Mount Sinai Health System and principal investigator of the study, said in an interview. 

“And when the patient tries to move their right ankle, same idea. The stent can pick up that signal and decode it and say ‘Ok, the patient is trying to move their right ankle. Let’s make that the right click.’ And so on and so forth as it builds out and identifies more signals over time,” Putrino said. 

The procedure is advantageous for several reasons. Stents have been widely used in medicine for decades. The small mesh tubes are used to hold open passages in the body, such as weak or narrowed arteries. Many neurosurgeons and cardiologists are familiar with the technique, so the skillset is transferable. Putrino said this makes a large difference in the risk profile for the procedure and the long-term feasibility of the technology. 

Implants that go directly into the brain also cause scar tissue around the electrodes which makes it hard to record brain activity over time, which is not the case with the Stentrode. 

“Over time as the stent becomes more and more continuous with the blood vessel, it becomes easier for the electrodes on the stent to record brain activity,” Putrino said. 

The first human trials of the technology were carried out in Australia and found the device was generally safe with no serious adverse events after following participants for a year. The Stentrode also stayed in place in patients and the blood vessel in which the device was placed remained open. Participants successfully used a computer to communicate by text and perform tasks such as online shopping and banking. 

In a Ted Talk earlier this year, Synchron CEO Thomas Oxley showcased a study participant who sent a tweet using the device, as well as two others who communicated with him via text. 

“I think brain-computer interface is an example of a type of tool that is going to be used as we unlock the brain and start to treat conditions that were previously untreatable and previously impossible,” Oxley said in an interview. 

“I really feel like we’re in this renaissance period that’s emerging. I think it’s as corollary to what happened with the sequencing of the genome. We first had to figure out how to sequence the genome. There was all this information. Then we started creating tools to engage with the genome, and it spawned the entire industry of new areas of medicine that we can do by manipulating the genome. The same thing is happening in the brain.”

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