Stentrode Device Allows Computer Control by ALS Patients With Partial Upper Limb Paralysis

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by Steve Bryson, PhD |

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Stentrode device

The Stentrode, a minimally invasive, fully implanted wireless device that transmits signals from the brain’s motor cortex, can help people with upper limb paralysis control a digital device without using their hands, a study shows.

In a first-in-human experience, the device has been implanted successfully into two people with amyotrophic lateral sclerosis (ALS) who could not move their upper limbs. A couple of months after implantation, patients could control a computer and complete daily tasks such as online banking, shopping, and texting.

The study, “Motor neuroprosthesis implanted with neurointerventional surgery improves capacity for activities of daily living tasks in severe paralysis: first in-human experience,” was published in the Journal of NeuroInterventional Surgery

People with ALS live with impaired voluntary motor function and lose the ability to engage in daily activities such as regularly communicating with family and peers, shopping, and financial management. 

However, despite the loss of nerve cells that control motor function, the motor cortex remains intact in a significant number of patients. 

Brain-computer interfaces (BCIs) aim to restore voluntary motor control of digital devices, such as computers, in paralyzed people by converting the intent to move nerve impulses from a functioning motor cortex into a digital signal.

Electrodes placed on the scalp have shown the ability to translate signals into device control. Still, the complex daily setup by caregivers or technicians limits this approach in an everyday living setting. 

The Stentrode, developed by Synchron in California, along with scientists at The University of Melbourne in Australia, is a small electrode device designed to be implanted into blood vessels in the brain next to the motor cortex without the need for open-brain surgery. The device expands and grows into vessel walls without blocking blood flow.

The Stentrode captures brain activity associated with intended movement and sends these signals through a wire to a small device implanted just under the skin on the chest, which can be connected to a computer wirelessly. 

This study (NCT03834857) reported the successful implantation of the Stentrode in two people with ALS who were unable to completely control their upper limbs and details how they were trained to control a computer and perform specific tasks. 

“We are excited to report that we have delivered a fully implantable, take home, wireless technology that does not require open brain surgery, which functions to restore freedoms for people with severe disability,” Thomas Oxley, MD, PhD, CEO of Synchron and professor at The University of Melbourne, said in a press release.  

Participant 1 was in their 70s and was diagnosed with ALS without dementia. Due to weakness in the upper limbs, the patient had lost the ability to use a personal computer or smartphone, which made the patient dependent on a caregiver. Eye-tracking and voice activation technology failed to help.

Participant 2 was in their 60s and also was diagnosed with ALS without dementia. Due to loss of power in their arms, the patient lost the use of a personal computer and digital devices, adversely affecting work-related activities and independent living at home. 

The Stentrodes were implanted under general anesthesia and guided by 3D imaging to direct a catheter through a small incision in the neck, through the jugular vein, and placed precisely next to the motor cortex in the brain. A small wire from this device was connected to another device called an internal telemetry unit (ITU), implanted just under the skin on the chest. 

Both patients were discharged home within four days of the implantation surgery. 

“This is the first time an operation of this kind has been done, so we couldn’t guarantee there wouldn’t be problems, but in both cases, the surgery has gone better than we had hoped,” said trial lead investigator Peter Mitchell, MD, professor at The Royal Melbourne Hospital. “The procedure isn’t easy, in each surgery there were differences depending on the patient’s anatomy, however in both cases the patients were able to leave the hospital only a few days later, which also demonstrates the quick recovery from the surgery.”

Following a period of wound recovery and optimization of radio communication between ITU and computer for data flow, device training was conducted at home with assistance from a neuroscientist using Synchron’s custom training software. 

Participants’ movements were mapped using a variety of movement-attempts, including fist-clenching, foot-tapping, and knee extension. Patients then used the resulting signals to react to on-screen cues combined with an eye-tracker to control a cursor movement, which generated one of three potential commands; no click, short click, or long-click. The training period ended when the average click selection accuracy was 90% or more. 

For participant 1, unsupervised home use began 86 days after implantation and achieved a typing task average click selection accuracy of 92.63%, across 748 selections over 129 trials. Correct characters per minute with predictive text disabled was a rate of 13.81. 

Participant 2 began using the device 71 days after implantation and achieved an average click selection accuracy of 93.18%, across 569 selections made in 95 trials. The correct characters per minute, with predictive text disabled for this patient, was 20.10.

Both participants completed all assigned everyday tasks, such as text, email, shopping, and finance. 

No serious adverse side effects were reported for either participant, and there were no device-related adverse side effects, including infection or headache. Immediately following implantation, participant 1 fainted for a short period of time but required no further intervention.

“Observing the participants use the system to communicate and control a computer with their minds, independently and at home, is truly amazing,” said Nicholas Opie, PhD, professor at the University of Melbourne. “We are thankful to work with such fantastic participants, and my colleagues and I are honoured to make a difference in their lives. I hope others are inspired by their success.

“Over the last eight years we have drawn on some of the world’s leading medical and engineering minds to create an implant that enables people with paralysis to control external equipment with the power of thought. We are pleased to report that we have achieved this,” he added. 

“These first in-human data demonstrate the potential for an endovascular motor neuroprosthesis to achieve digital device control with multiple commands in people with paralysis and, when combined with eye-tracking, to improve functional independence,” the researchers wrote.

The scientists cautioned it might be a few years before this technology is publicly available. To support further researchers and enroll more patients, the trial recently received an AU$1.48 million grant ($1.04 million U.S.) from the Australian government to expand the trial to hospitals in New South Wales and Queensland.