Neuralink brain implants: Neuralink's recent disclosure about tiny wires retracting from the brain of its first patient during a human trial highlights an issue the company has reportedly known about for years, according to five sources familiar with the matter.

These sources revealed that animal testing conducted prior to US approval last year indicated the potential for wires to retract, thereby removing sensitive electrodes designed to decode brain signals. Despite this, Neuralink considered the risk minor enough to forgo a redesign.

Neuralink's implant aims to allow paralysed patients to operate digital devices through thought alone, which could significantly aid individuals with spinal cord injuries. Last week, the company announced that some wires in the implant had retracted, reducing the number of electrodes available to monitor brain signals. These signals are crucial for translating brain activity into actions, such as moving a computer cursor.

Alternation on algorithm 

To address the issue, Neuralink modified its algorithm to improve sensitivity and restore the implant's functionality in monitoring the patient’s brain signals.

The sources, bound by confidentiality agreements, remained anonymous. Neuralink and its executives did not respond to requests for comment. The US Food and Drug Administration (FDA) was aware of the potential issue from the animal testing results included in Neuralink's application for human trials, according to one source. However, the FDA did not comment on the issue's significance but stated it would continue to monitor the safety of the study's participants.

Continuing the trials without redesigning the wires could pose challenges if more wires retract and the algorithm tweaks prove insufficient, one source suggested. However, redesigning the threads carries its own risks, such as potential brain tissue damage if the threads need to be removed, according to two sources.

Easily removable threads

Neuralink has aimed to make the threads easily removable to facilitate updates as technology advances, current and former employees said. The company implanted the device in the brain of its first patient, Noland Arbaugh, who is paralysed from the shoulders down due to a 2016 diving accident, in January.

In the weeks following the surgery, several threads retracted, Neuralink noted in a blog update last week, which did not mention any adverse health effects for Arbaugh or specify how many of the device’s 64 threads were affected. The device has allowed Arbaugh to play video games, browse the internet, and move a computer cursor by thought alone. Neuralink reported that Arbaugh quickly surpassed the world record for controlling a cursor with his mind.

Difficult problem to solve

Outside researchers and former employees of medical device companies acknowledge that it is common for design issues to arise during animal and clinical testing. Specialists in brain implants note that thread movement can be a difficult problem to solve due to the brain’s natural movement within the skull.

Robert Gaunt, a neural engineer at the University of Pittsburgh, described the wire movement shortly after surgery as disappointing but not unforeseen, noting that the initial period after implantation is the most vulnerable.

In 2022, the FDA initially rejected Neuralink’s application for human trials, raising concerns about the threads, as Reuters reported last year. Neuralink conducted additional animal testing to address these concerns, receiving FDA approval for human trials last year.

The company found that some pigs implanted with the device developed granulomas, a type of brain inflammation, which raised concerns among researchers that the threads might be the cause. In one severe case, a pig developed a fever and was heaving post-surgery. It was only after examining the pig’s brain post-mortem that the extent of the problem was understood.

Internally, Neuralink researchers debated how to address the issue and undertook a lengthy investigation. Ultimately, they could not determine the cause of the granulomas but concluded that the device and its threads were not to blame, according to one source.

(With Reuters inputs)