A handful of "locked-in" amyotrophic lateral sclerosis (ALS) patients can now work a laptop computer using their brain waves, thanks to an implant lodged in a major vein inside their skull.
The implant - a stent lined with 16 miniscule electrodes - is nestled in a vein located near the motor cortex of completely paralyzed patients, the authors of a new study on the procedure explained.
"This device senses the electrical activity that occurs in the motor cortex when someone thinks about moving their limbs," said co-researcher Douglas Weber, a professor of mechanical engineering and neuroscience at Carnegie Mellon University, in Pittsburgh. "These movement signals are then transmitted to an external device where they are decoded from command signals that are sent to a computer, thus providing a direct communication link for the brain."
With the implant, patients can send emails and texts, browse the web, shop online or manage their personal finances, Weber noted.
"There's many activities of daily living that seem to be well supported by this device," he said.
This isn't the first research effort to use brain implants to help the paralyzed use computers or other electronic devices.
For example, a study released last week detailed the case of a locked-in German ALS patient who has regained the ability to communicate via two microchips implanted in his brain. That paper was published in the journal Nature Communications.
But this is the first attempt to place such an implant without removing part of the skull to access the brain, the researchers said.
Four patients with the neurodegenerative disease called ALS - also known as Lou Gehrig's disease - instead received their implant via a catheter threaded through one of the major veins that drain blood away from the brain, Weber said.
The catheter delivers the implant into a part of the vein near the brain. The implant then opens up and lines the walls of the vein, much as a normal stent expands to support the walls of a narrow or weak blood vessel in heart attack patients.
Once in place, the implant picks up signals from the motor cortex and relays them to an electronic decoder implanted in the person's chest, Weber said.
The decoder analyzes nerve signals when people think of certain movements - for example, tapping their foot or extending their knee - and translates those thoughts into computer navigation.
In combination with eye-tracking technology, those movement thoughts allowed patients to operate a laptop, Weber said. One of the patients got so good at it that they could control a computer independently, without an eye tracker.
The preliminary findings were presented Tuesday, in advance of the American Academy of Neurology (AAN) annual meeting, to be held from April 2 to 7 in Seattle. Such research is considered preliminary until published in a peer-reviewed journal.
Dr. Natalia Rost, chair of the AAN Science Committee, praised the "cross-pollination" of neuroscience and engineering in the study, noting that such efforts "sometimes yield some of the most exciting results."
The point of this small-scale study was mainly to show that the implant posed no safety hazards to patients.
"Obviously as a stroke doctor, I feel extremely strongly about the safety of these devices," said Rost, who is chief of the stroke division at Massachusetts General Hospital, in Boston. "There is a certain fear of God you instill in stroke doctors by inserting a device" into a major cranial vein.
In the new study, the researchers monitored the participants for one year, finding that the device stayed in place for all four patients and did not hamper blood flow.
"The device integrates well into the walls of the blood vessel over time," Weber said. "Certainly after implantation the device is exposed to the bloodstream, but once it becomes encapsulated and fully integrated into the blood vessel wall, I think the risks of thrombosis [clotting] diminish over time."
Since there have been no signs of clots or vein blockages in the initial patients, the research team has continued to recruit more people into a larger trial for the implant, Weber said.
The investigators plan to expand the trial to include patients who are severely paralyzed for reasons other than ALS, Weber said, potentially including severe stroke victims or people with a spinal cord injury.
"These are all people that may benefit from the assistive communication and digital communication functions that are supported by this technology," Weber said.
More information
The U.S. National Institutes of Health has more about ALS.
SOURCES: Douglas Weber, PhD, professor, mechanical engineering and neuroscience, Carnegie Mellon University, Pittsburgh, Pa.; Natalia Rost, MD, chief, stroke division, Massachusetts General Hospital; presentation, March 29, 2022, American Academy of Neurology annual meeting, Seattle
