Neuralink Exclusive-Musk has had problems with its tiny wires for years, sources say

By Rachael Levy

(Reuters) – Neuralink’s revelation last week that tiny wires inside its first patient’s brain had gone awry is an issue Elon Musk’s company has known about for years, according to five people familiar with the matter.

The company knew from animal testing it did before it got US approval last year that the wires could retract, touching the sensitive electrodes that decode brain signals, three of the sources said. Neuralink deemed the risk low enough to not merit the redesign, the sources added.

Neuralink is testing its implant to give paralyzed patients the ability to use digital devices by thinking on their own, a prospect that could help people with spinal cord injuries.

The company said last week that the implant’s tiny wires, which are thinner than a human hair, pulled from the patient’s brain in its first human trial, leaving fewer electrodes that could measure brain signals.

The signals are translated into actions, such as moving a mouse cursor on a computer screen. The company said it managed to restore the implant’s ability to monitor its patients’ brain signals by making changes including modifying its algorithm to be more sensitive.

The sources declined to be identified, citing confidentiality agreements they signed with the company. Neuralink and its executives did not respond to calls and emails seeking comment.

The US Food and Drug Administration was aware of the potential issue with the wires because the company had shared the animal test results as part of its application to begin human trials, said one of the people.

The FDA declined to comment on whether it was aware of the issue or its potential significance. The agency told Reuters it would continue to monitor the safety of patients enrolled in the Neuralink study.

If Neuralink were to continue the trials without a redesign, it could face challenges if more wires were pulled out and the change to the algorithm wasn’t enough, one of the sources said.

But redesigning threads comes with its own risks. Cultivating them in the brain could lead to brain tissue damage, for example, if the threads loosen or the company needs to remove the device, two of the sources said.

The company has tried to design the threads in a way that makes them seamless, so the implant can be updated over time as technology improves, current and former employees say.

In January, Neuralink implanted the device into the brain of its first patient, Noland Arbaugh, who is paralyzed from the shoulders down as a result of a 2016 diving accident.

In the weeks following the surgery, “some threads pulled back from the brain,” Neuralink said in a blog update last week. The post made no mention of adverse health effects on Arbaugh and did not disclose how many of the device’s 64 threads pulled out or stopped collecting brain data.

So far, the device has allowed Arbaugh to play video games, browse the internet and move a computer cursor on his laptop by thinking on his own, according to the company’s blog posts and videos. Neuralink says that soon after the surgery, Arbaugh broke the world record for the speed at which he can control a cursor with thoughts alone.

It is common for medical device companies to troubleshoot various designs during animal trials and problems that arise during animal and clinical testing, according to researchers and outside sources who have worked at Neuralink and other medical device companies.

Specialists who have studied brain implants say that the issue of moving threads can be difficult to resolve, in part because of the mechanics of how the brain moves inside the skull.

Robert Gaunt, a neural engineer at the University of Pittsburgh, described the movement of the wires so soon after the surgery as disappointing but said it is not unexpected. “In the immediate days, weeks, months after an implant like this, it’s probably the most vulnerable time,” he said.


In 2022, the FDA initially rejected Neuralink’s request to begin human trials, and raised safety concerns about the threads, Reuters reported exclusively last year.

Neuralink conducted additional animal testing to address those concerns, and the FDA last year gave the company permission to begin human testing.

The company found that a subset of pigs implanted with its device developed a type of inflammation in the brain called granulomas, raising concerns among Neuralink researchers that the threads could be the cause, according to three sources familiar with the matter and who have seen records. Reuters.

Granulomas are an inflammatory response of tissue that may be caused by a foreign object or infection.

In at least one case, a pig developed a severe case of the condition. Company records reviewed by Reuters show the pig developed a fever and was heaving after surgery. Neuralink researchers did not recognize the extent of the problem until the pig’s brain was examined post-mortem.

Within Neuralink, the researchers discussed how to solve the problem and began a month-long investigation, the sources familiar with the proceedings said.

Ultimately, the company could not determine the cause of the granulomas, but concluded that the device and the threads attached were not to blame, one of the sources said.

(Reporting by Rachael Levy and Marisa Taylor in Washington; Editing by Greg Roumeliotis and Bill Berkrot)

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