Synchron Halts Brain Implant Trials Over Signal-Cable Flaw

Synchron has paused clinical trials of its second-generation brain implant after the device failed to perform as expected in initial study participants, WIRED has learned. The Brooklyn-based startup, a competitor to Elon Musk's Neuralink, is also restructuring: it is eliminating jobs, scaling back its New York footprint, and building a team in San Diego to develop an entirely new device.

The pause matters beyond one company. Synchron's trials are the required gateway to a larger pivotal trial, which the US Food and Drug Administration needs before it can grant marketing approval for the device. The company was estimated at a nearly $1 billion valuation after closing a $200 million funding round last fall, with backing from Khosla Ventures and the venture firms of Bill Gates and Jeff Bezos. A hardware stumble at this stage signals how far implanted brain-computer interfaces remain from commercial availability for patients.

What went wrong with the device?

Synchron's core technology, the Stentrode, is a stent-like mesh tube that does not require brain surgery. Surgeons insert it into the jugular vein at the base of the neck and guide it with a catheter until it sits on top of the brain's motor cortex. The company has promoted the approach as minimally invasive because the implant never rests in the brain itself.

The first-generation Stentrode connected through an external wire resting on a user's chest. Ten volunteers across the US and Australia received that device and used it to send emails, text, browse the internet, and do online shopping and banking with their thoughts. Synchron has also enabled volunteers to control an Amazon Alexa and Apple's iPad and Vision Pro without using their hands or voice.

The second-generation device is different in two respects: it has fewer electrodes, and it is fully wireless, connecting via Bluetooth. Synchron launched a multisite trial of the newer Stentrode in the US earlier this spring, with sister sites in Australia and Canada. Some participants have already received implants. Those sites recently paused enrollment because the device is not working as intended, according to sources familiar with the trials who asked to remain anonymous.

In a statement to WIRED, Synchron says it voluntarily paused enrollment "after identifying a performance issue involving the lead, the cable that carries signals from the Stentrode to the implanted electronics."

"The issue does not involve the Stentrode itself and no safety issues related to the device have been identified. The pause was a company decision, not an FDA-directed action," the statement continues.

The company has since brought lead design and manufacturing in-house. Rather than fixing the lead alone, Synchron says it is upgrading the whole Stentrode system and will resume trial enrollment once the hardware upgrades are complete.

"We will continue to support participants with Stentrode devices across their lifetime. Our commitment to their care and well-being remains unchanged," Synchron says.

How did the trial sites respond?

Two of the five US trial sites that WIRED was able to reach confirmed that recruitment is on hold at those locations. A coordinator at one site said the pause was not safety-related and reflected Synchron taking a look at the device to make sure the company is getting the readouts it is looking for.

The distinction between a performance issue and a safety issue is consequential for the field. Device failures that harm patients trigger far stricter regulatory scrutiny than signal-quality problems, and Synchron has moved to frame its pause firmly in the second category.

CEO Tom Oxley has not softened the company's clinical ambition. "We still have strong confidence that it has the potential to be a first-line therapy," Oxley says of the Stentrode.

Why is Synchron moving to San Diego?

Synchron's website and LinkedIn page list around a dozen job openings in San Diego, including electrical and mechanical engineers, microchip designers, and materials scientists. The new team will design and manufacture the upgraded lead and Stentrode.

The San Diego group will also build a separate, unrevealed device that will go "beyond the blood vessels altogether," according to the company's website. Oxley previously told WIRED that Synchron planned to develop a device reaching multiple brain regions at once, which could allow more complex and natural functions beyond moving a cursor or making a mouse click.

The restructuring carries a human cost the company has not quantified. Synchron confirmed job eliminations and a reduced New York presence but disclosed no headcount figures, no timeline for the hardware upgrades, and no date for resuming enrollment.

How does this compare with Neuralink's troubles?

Synchron is not the first implant maker to hit hardware problems in humans. Neuralink, reportedly valued as high as $42 billion in secondary market transactions as of this summer, experienced an early failure with its implant in 2024. The coin-sized device sits in the skull and has 64 tiny, flexible wires threaded into the brain.

A few weeks after Neuralink's first volunteer, Noland Arbaugh, received the device, several of the wires came out of his brain, causing a loss of cursor control. Neuralink compensated for the lost threads and restored control by modifying its recording algorithm — a software fix that kept the trial running without explanting the device.

Synchron's problem is different in kind. Its lead is a physical cable carrying signals from the Stentrode to implanted electronics, and the company has chosen a hardware overhaul rather than an algorithmic patch. That decision pushes back the timeline to the pivotal trial that FDA marketing approval requires.

What role does AI play in the field's momentum?

The brain-computer interface field is expanding rapidly, with money pouring into companies pursuing both implanted devices and wearables. Recent advances in artificial intelligence are fueling that growth, because AI models can read brain patterns faster and more accurately than traditional algorithms.

The clearest example arrived in January. Merge Labs, a brain-computer interface company cofounded by OpenAI CEO Sam Altman, came out of stealth with $252 million in funding. OpenAI provided some of that money, and the two companies are collaborating on AI models.

That capital flow sets the stakes for Synchron's recovery. A company once estimated at nearly $1 billion, backed by some of the most prominent investors in technology, is now racing to redesign its hardware while better-funded rivals advance and AI-native entrants enter the field.

These devices have shown remarkable promise for people with severe motor disorders. They remain experimental. Synchron's setback shows how far the field still has to go before these systems are commercially available for patients — and the pace of that gap-closing now depends on how quickly an entirely new device comes out of San Diego.