Category: Implants and Prostheses

Brain Implants ‘Turn the Lights Back on’ for Cognitive Function after TBI

Deep brain stimulation illustration. Credit: NIH

Moderate to severe traumatic brain injury carries lasting effects: trouble with focussing, recall and decision-making. Though many recover enough to live independently, their impairments prevent them from returning to school or work and from resuming their social lives. Current treatments offer little improvement, but results of a clinical trial of a new brain stimulation device, published in Nature Medicine, have shown great promise in at least partially restoring cognitive function.

“In general, there’s very little in the way of treatment for these patients,” said Jaimie Henderson, MD, professor of neurosurgery and co-senior author of the study.

But the fact that these patients had emerged from comas and recovered a fair amount of cognitive function suggested that the brain systems that support attention and arousal – the ability to stay awake, pay attention to a conversation, focus on a task – were relatively preserved.

These systems connect the thalamus, a relay station deep inside the brain, to points throughout the cortex, the brain’s outer layer, which control higher cognitive functions.

‘Dimmed lights’

“In these patients, those pathways are largely intact, but everything has been down-regulated,” said Henderson, the John and Jene Blume-Robert and Ruth Halperin Professor. “It’s as if the lights had been dimmed and there just wasn’t enough electricity to turn them back up.”

In particular, an area of the thalamus called the central lateral nucleus functions as a hub that regulates many aspects of consciousness.

“The central lateral nucleus is optimised to drive things broadly, but its vulnerability is that if you have a multifocal injury, it tends to take a greater hit because a hit can come from almost anywhere in the brain,” said Nicholas Schiff, MD, a professor at Weill Cornell Medicine and co-senior author of the study.

The researchers hoped that precise electrical stimulation of the central lateral nucleus and its connections could reactivate these pathways, turning the lights back up.

Precise placement

In the trial, the researchers recruited five participants who had lasting cognitive impairments more than two years after moderate to severe traumatic brain injury. They were aged 22 to 60, with injuries sustained three to 18 years earlier.

The challenge was placing the stimulation device in a small target in the right area, which varied across individuals. Each brain is shaped differently to begin with, and the injuries had led to further modifications.

“That’s why we developed a number of tools to better define what that area was,” Henderson said. The researchers created a virtual model of each brain that allowed them to pinpoint the location and level of stimulation that would activate the central lateral nucleus.

Guided by these models, Henderson surgically implanted the devices in the five participants.

“It’s important to target the area precisely,” he said. “If you’re even a few millimetres off target, you’re outside the effective zone.”

A pioneering moment

After a two-week titration phase to optimise the stimulation, the participants spent 90 days with the device turned on for 12 hours a day.

Their progress was measured by a standard test of mental processing speed, called the trail-making test, which involves drawing lines connecting a jumble of letters and numbers.

“It’s a very sensitive test of exactly the things that we’re looking at: the ability to focus, concentrate and plan, and to do this in a way that is sensitive to time,” Henderson said.

At the end of the 90-day treatment period, the participants had improved their speeds on the test, on average, by 32%, far exceeding the 10% the researchers had aimed for.  

“The only surprising thing is it worked the way we predicted it would, which is not always a given,” Henderson said.

For the participants and their families, the improvements were apparent in their daily lives. They resumed activities that had seemed impossible – reading books, watching TV shows, playing video games or finishing a homework assignment. They felt less fatigued and could get through the day without napping.

The therapy was so effective the researchers had trouble completing the last part of their study. They had planned a blinded withdrawal phase, in which half the participants would be randomly selected to have their devices turned off. Two of the patients declined, unwilling to take that chance. Of the three who participated in the withdrawal phase, one was randomized to have their device turned off. After three weeks without stimulation, that participant performed 34% slower on the trail-making test.

The clinical trial is the first to target this region of the brain in patients with moderate to severe traumatic brain injury, and it offers hope for many who have plateaued in their recovery.

“This is a pioneering moment,” Schiff said. “Our goal now is to try to take the systematic steps to make this a therapy. This is enough of a signal for us to make every effort.”

Source: Stanford Medicine

No-aspirin Regimen Benefits Heart Failure Patients with LVADs

Photo by cottonbro studio

A recent clinical trial published in JAMA found that excluding aspirin for advanced heart failure (HF) patients with a ventricular assist device saw a reduction in bleeding events while maintaining their survival rates.

The ARIES-HM3 Randomised Clinical Trial assessed the safety and efficacy of excluding aspirin from the antithrombotic regimen in patients with advanced HF who have undergone implantation of a fully magnetically levitated left ventricular assist device (LVAD).

“We can now safely say that not giving aspirin is not only safe from a thromboembolic risk profile but results in improved adverse event rate by a significant reduction in non-surgical bleeding which is a well-known complication related to LVAD therapy,” said Mirnela Byku, MD, P.D, MBA, co-author of the study and director of the UNC Durable Mechanical Circulatory Device Program at the UNC School of Medicine.

“Improving not only longevity but also reducing morbidity and improving quality of life is a big focus in the field of MCS.”

Until this study, there had been no consensus in the field about use of or dose of aspirin in the LVAD population.

The international clinical trial followed a randomised, double-blind, placebo-controlled design and involved 628 patients across 51 centres in 9 countries.

The patients were divided into two groups: one receiving aspirin (100mg/d) and the other receiving a placebo in addition to vitamin K antagonist (VKA) therapy.

A focus was to determine if the likelihood a patient experiences major nonsurgical haemocompatibility-related adverse events (such as stroke, pump thrombosis, major bleeding, or arterial peripheral thromboembolism) within 12 months differed between the two groups.

The results showed that not giving aspirin to patients with advanced HF, treated with a fully magnetically levitated LVAD who are receiving VKAs, did not make their survival worse. Furthermore, aspirin avoidance was associated with a significant reduction (34%) in major nonsurgical bleeding events.

Source: University of North Carolina Health Care

‘Cyberpunk’ Inspired Finger Prostheses will be Available to All via 3D Printing

A groundbreaking, easy-to-use 3D printable finger prosthesis created by a recent University of Houston graduate could offer amputees a low-cost solution to restore finger functionality. David Edquilang first designed Lunet, which doesn’t need metal fasteners, adhesives or special tools to assemble, as an undergraduate student at the Gerald D. Hines College of Architecture and Design. While standard prostheses can cost thousands of dollars, Edquilang aims to make his design open access on the internet, instead of selling it.

Edquilang explains: “Lunet began when I decided to design and 3D print prototype finger mechanisms for a prosthetic hand for fun in my free time. 2 weeks and 18 prototypes later, I created a mechanism and finger structure that closely replicated the range of motion of real fingers.”

Edquilang’s mentor at UH was Associate Professor Jeff Feng, co-director of UH’s Industrial Design program. Through a partnership with Harris Health System, Feng learned of a patient who had her fingers amputated due to frostbite. Inspired by working on an upper limb prosthesis Edquilang previously developed with student Niell Gorman, working closely with Professor Feng, Edquilang created prosthetic fingers that returned mobility to the patient, allowing her to pick up objects again.

Edquilang continues: “My professor and I were then referred to a finger amputee who lost 3 of her fingers. I applied the mechanism I created to design a finger prosthesis for her. Nearly 40 design iterations and multiple rounds of patient testing were performed to ultimately create a functional prosthesis that fit her.

His “breakthrough” came from a literal break in his design.

“After we finished working with this amputee patient, I continued to tinker with my finger designs. I intentionally broke one of my finger prototypes to see where its structural weakpoint is. It broke at the distal knuckle. This led to me having a breakthrough in the design. I added a linkage that replaces the previously rigid distal knuckle, and I stumbled upon inventing a novel finger mechanism that was more flexible and nearly unbreakable. I then set on refining the design to be more functional, easily 3D printable, and more visually appealing. Inspiration from cyberpunk art and fighter jets influenced the design. 28 design iterations and a myriad of prototypes later resulted in Lunet.”

“It feels great knowing you have the capability to positively impact people’s lives and give them help they otherwise wouldn’t be able to get,” said Edquilang.

“Not every good idea needs to be turned into a business. Sometimes, the best ideas just need to be put out there ,” said Edquilang, who graduated with a Bachelor of Science in Industrial Design last year. “Medical insurance will often not cover the cost of a finger prosthesis, since it is not considered vital enough compared to an arm or leg. Making Lunet available online for free will allow it to help the greatest number of people.”

Lunet wins awards

The prosthetic design garnered Edquilang a 2023 Red Dot: Luminary award, the highest level of recognition accorded at the Red Dot Award: Design Concept. He and Feng took home the coveted accolade at Red Dot’s ceremony last month in Singapore.

“Good results come from dedication. Extraordinary results come from experimentation. Incredible results come from a combination of both,” he said upon winning the award. He has also received a number of other accolades, including iFDesign, and national runner up for the James Dyson Award.

“David’s recent success in winning the most prestigious design awards across the world is the best manifestation of the unparalleled education and training students experience in our Industrial Design program,” Feng said. “Built upon a belief that every student is a creative individual, the program pedagogy focuses on methods of cultivating innovative minds, which is enforced with rigorous professional training.”

Lunet’s geometry inspired its name

Lunet is made up of two common types of 3D printed plastics: polylactic acid and thermoplastic polyurethane. Each finger is made up of four parts held together by plastic pins. Edquilang describes arcs and circular orbits as the foundation for the motion of the finger mechanism. The geometric basis of the design evoked the idea that the prosthesis orbits around the user’s joints like a moon, or lunet, hence the name.

Another element of Lunet’s uniqueness is that it is nearly impossible to break; other finger prosthetics can be complicated and require many parts.

“The problem with higher mechanical complexity is that these designs are less durable,” Edquilang said. “The more parts you have, the more points of failure. You need to make prosthetic fingers robust and as strong as possible, so it doesn’t break under normal use, yet you want the design to be simple. This was one of the greatest challenges in making Lunet.”

He encourages other design students not to be afraid to experiment and fail because that is often how one can learn to improve the most.

“Where the world has an abundance of problems, designers have an abundance of talent, and we should not be selfish with it,” Edquilang said.

Source: University of Houston

Mapping the ‘Light’ Seen by Closed Eyes could Help Prosthetic Eyes See Better

Photo by on Unsplash

Researchers at Monash University have identified a new way of mapping ‘phosphenes’ – the visual perception of the bright flashes we see when no light is entering the eye – to improve the outcome of surgery for patients receiving a cortical visual prosthesis.

Cortical visual prostheses are devices implanted onto the brain with the aim of restoring sight by directly stimulating the area responsible for vision, the visual cortex, bypassing damage to the retina of the eye or the optic nerve. Phosphenes, apparent flashes and patterns of lights, were described by the ancient Greeks and can be elicited by pressure, injury, disease, certain medications or direct electrical stimulation.

A typical prosthesis consists of an array of fine electrodes, each of which is designed to trigger a phosphene. Given the limited number of electrodes, understanding how electrodes can best be placed to generate useful perceived images becomes critical.

Published in the Journal of Neural Engineering, the study presents a more realistic simulation for cortical prosthetic vision.

As part of this researchers from the Department of Electrical and Computer Systems Engineering at Monash University, led by Associate Professor Yan Tat Wong, are honing in on the ideal distribution of phosphenes.

“Phosphenes are likely to be distributed unevenly in an individual’s visual field, and differences in the surface of the brain also affect how surgeons place implants, which together result in a phosphene map unique to each patient,” Associate Professor Wong said.

The study used a retinotopy dataset based on magnetic resonance imaging (MRI) scans, consulting with a neurosurgeon about realistic electrode implantation sites in different individuals, and applying a clustering algorithm to determine the most suitable regions to present stimuli.

Sighted participants recruited for the study were asked to test and verify the phosphene maps based on visual acuity and object recognition.

“We’re proposing a new process that incorporates our simulation paradigm into surgical planning to help optimise the implantation of a cortical prosthesis,” Associate Professor Wong said.

The process would begin with an MRI scan to plot the recipient’s brain surface in the area of the visual cortex. Potential implant locations would then be identified, and the simulation developed in the Monash research would be used to plot phosphene maps.

“We can use the metrics we computed to find practical implant locations that are more likely to give us a usable phosphene map, and we can verify those options through psychophysics tests on sighted participants using a virtual reality headset,” Associate Professor Wong said.

“We believe this is the first approach that realistically simulates the visual experience of cortical prosthetic vision.”

Source: Monash University

Mastering a Third Robotic Arm is Surprisingly Quick

Interfaces for DoF augmentation (figure by Tobias Pistohl). From Eden at al., Nature Communications. 2022

Busy doctors and nurses may have often found themselves wishing they had an extra arm to help with a patient or help with a difficult suture. Researchers around the world are developing supernumerary robotic arms to help workers achieve certain tasks unaided, or with less strain – but how long would it take to master learning an additional limb? The answer is: not long at all. One hour’s worth of training is enough for people to carry out a task with their ‘third arm’ as effectively as with a partner, according to the results of a new study published in IEEE Open Journal of Engineering in Medicine and Biology.

A new study by researchers at Queen Mary University of London, Imperial College London and The University of Melbourne has found that people can learn to use supernumerary robotic arms as effectively as working with a partner in just one hour of training.

The study investigated the potential of supernumerary robotic arms to help people perform tasks that require more than two hands. The idea of human augmentation with additional artificial limbs has long been a staple of science fiction.

Demonstrating performing a suture with an assistant robotic arm.

“Many tasks in daily life, such as opening a door while carrying a big package, require more than two hands,” said Dr Ekaterina Ivanova, lead author of the study from Queen Mary University of London. “Supernumerary robotic arms have been proposed as a way to allow people to do these tasks more easily, but until now, it was not clear how easy they would be to use.”

The study involved 24 participants who were asked to perform a variety of tasks with a supernumerary robotic arm. The participants were either given one hour of training in how to use the arm, or they were asked to work with a partner.

The results showed that the participants who had received training on the supernumerary arm performed the tasks just as well as the participants who were working with a partner. This suggests that supernumerary robotic arms can be a viable alternative to working with a partner, and that they can be learned to use effectively in a relatively short amount of time.

“Our findings are promising for the development of supernumerary robotic arms,” said Dr Ivanova. “They suggest that these arms could be used to help people with a variety of tasks, such as surgery, industrial work, or rehabilitation.”

Source: Queen Mary University of London

A New Way to Map the Human Auditory Pathway

Photo by Brett Sayles

Researchers have developed a non-invasive method for mapping the human auditory pathway, which could potentially be used as a tool to help clinicians decide the best surgical strategy for patients with profound hearing loss. The findings, published online in the journal eLife, highlight the importance of early interventions to give patients the ability to hear and understand speech, so that their auditory-language network can develop properly and their long-term outcomes are improved.

Sensorineural hearing loss (SNHL) occurs when the sensitive hair cells inside the cochlea are damaged, or when there is damage to the auditory nerve which transmits sound to the brain. A person with profound hearing loss is typically unable to hear any sounds, or at best, only very loud sounds. Congenital SNHL has increased in prevalence over the past two decades, from 1.09 to 1.7 cases per 1000 live births.

The sound of speech is carried through the brain by nerve fibres in regions known as the auditory pathway, and are processed in a region called the language network. In cases of congenital SNHL, the lack of speech inputs reaching the language network may hinder its proper development, leading to poorer spoken language skills.

Currently, the primary treatments for profound SNHL are cochlear and auditory brainstem implantation, where a device is used to stimulate the peripheral cochlea or the central cochlear nucleus, respectively. Both techniques can partially restore hearing in patients, but their language development outcomes can vary. This is especially true for patients with inner ear malformations (IEM) or cochlear nerve deficiencies (CND), which contribute to 15-39% of congenital SNHL cases.

“Where SNHL is caused by CNDs and/or IEMs, there is a great deal of uncertainty around the best method of treatment. This is due to the difficulty of assessing the condition of the cochlear nerve and distinguishing between certain types of IEM, both of which impact surgical decision making,” says senior authors Hao Wu, a professor and Chief Physician specialising in Otolaryngology at Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, China. Wu also serves as the Hospital Administrator and the Clinical and Academic Lead for the department. “We therefore need a more effective method for mapping the auditory pathway and diving deeper into how IEMs and CNDs affect the development of the auditory-language network.”

In their study, professor Wu’s team investigated the auditory and language pathways in 23 children under the age of six. They included 10 children with normal hearing, and 13 with profound SNHL. In the latter group, seven children had received cochlear implantations, two had received auditory brainstem implantations, and four were candidates for auditory brainstem implantations.

The human auditory pathway is difficult to investigate non-invasively due to its delicate and intricate subcortical structures located deep within the brain. To navigate this, the team developed a new methodology to reconstruct the pathway. First, they segmented the subcortical auditory structures using track density imaging, which are reconstructed from a specific type of MRI scan and provide much greater detail and information on the structural connectivity of the brain. This allowed them to delineate the cochlear nucleus and the superior olivary complex of the auditory pathway. They then tracked the auditory and language pathways using a neuroimaging technique called probabilistic tractography, which uses the information from an MRI scan to provide the most likely view of structural brain connectivity. Next, the team assessed the density and cross-section of the nerve fibres in the auditory and language pathways.

This combined methodology allowed them to investigate three key areas to inform surgical decision making: the condition of the nerve fibres in the auditory-language network of children with profound SNHL; the potential impact of IEMs and CNDs on the development of the network before surgical intervention; and the relationship between the pre-implant structural development of the network and the auditory-language outcomes following implantation.

The team’s observations revealed a lower nerve fibre density in children with profound SNHL, in comparison to those with normal hearing. This reduction was most pronounced in two regions of the inferior central auditory pathway, as well as the left language pathway.

In addition, the findings revealed that the language pathway is more sensitive than the central auditory system to IEMs and/or CNDs, implying that the structural development of the language pathway is more negatively impacted by the condition of the peripheral auditory structure. However, the authors caution that further study is required to validate this finding. As it is more difficult to image the central auditory pathway than the language pathway, this difference could have arisen due to the limitations of current neuroimaging technologies.

The authors say the study is also limited by a relatively small cohort of patients and an incomplete genetic dataset, so more studies with a more diverse patient population will also be needed. But with further validation, they add that the methodology could be used more widely for informing decisions in treating profound SNHL.

Source: eLife

Redo Transcatheter Procedure is a Reasonable Treatment for Select Patients

Photo by Natanael Melchor on Unsplash

Cedars-Sinai investigators have shown that redo transcatheter aortic valve replacement (TAVR) procedures are both safe and effective when compared with situations in which patients with similar risk profiles undergo the same procedure for the first time.

The novel findings, which appear in The Lancet, are significant because recent randomised clinical trials have shown that TAVR is a meaningful treatment option for both younger and lower-risk surgical patients.

“We now know that redo TAVR with balloon-expandable valves may be a reasonable treatment for failed TAVR procedures in select patients,” said Raj Makkar, MD, Cedars-Sinai’s vice president of Cardiovascular Innovation and Intervention and the study’s senior author. “This is increasingly important, as the patients treated with TAVR are younger than they were a decade ago, meaning they will likely need a repeat procedure at some point in their lifetime.”

At both the 30-day post-procedure mark and at one year, Makkar’s team found no difference between redo TAVR or first-time TAVR in terms of death or stroke rates.  

“Our findings also suggest that redo TAVR was associated with a significant improvement in quality of life,” said Makkar, who is also the associate director of the Smidt Heart Institute at Cedars-Sinai, director of the Interventional Cardiology Division in the Department of Cardiology, and the Stephen R. Corday, MD, Chair in Interventional Cardiology.

Transcatheter aortic valve replacement is a procedure that replaces a diseased aortic valve with a man-made valve. The procedure is now the standard treatment for patients with symptomatic severe aortic valve stenosis (narrowing of the artery).

The research team accessed a national database of all consecutive patients undergoing commercial TAVR in the US. Among the 350 591 patients who underwent TAVR between November 2011 and December 2022, 1320 individuals required redo procedures. The patients who underwent a repeat procedure had a mean age of 78 years old. About 58% were male and 42% female. 

“Fixing damaged valves is something in which we excel at the Smidt Heart Institute,” said Eduardo Marbán, MD, PhD, professor and executive director of the Smidt Heart Institute. “Our finding that TAVR can be redone safely is yet another step in establishing this as the default technology for aortic valve disease.”

Interventionalists in the Smidt Heart Institute at Cedars-Sinai have successfully completed more than 6000 minimally invasive transcatheter aortic valve replacements to date, with more than 650 performed in fiscal year 2022.

Source: Cedars-Sinai

Implanted Bioreactors Functioning as Artificial Kidneys Could One Day Replace Dialysis

Photo by Robina Weermeijer on Unsplash

Scientists at UC San Francisco are working on a new approach to treating kidney failure that could one day free people from needing dialysis or a transplant and the associated immunosuppressive drugs.

The technology, described in Nature Communications, shows for the first time that kidney cells, housed in an implantable device called a bioreactor, can survive inside the body of a pig and mimic several important kidney functions. The device can work quietly in the background, like a pacemaker, and does not trigger the recipient’s immune system to go on the attack.

Eventually, scientists plan to fill the bioreactor with different kidney cells that perform vital functions like balancing the body’s fluids and releasing hormones to regulate blood pressure, then pair it with a device that filters waste from the blood.

The aim is to produce a human-scale device to improve on dialysis, which keeps people alive after their kidneys fail but is a poor substitute for having a real working organ. In the US, more than 500 000 require dialysis several times a week. Many seek kidney transplants, but there are not enough donors, and only about 20 000 people receive them each year. An implantable kidney would be a boon.

This is a key step forward is for The Kidney Project, which is jointly headed by UCSF’s Shuvo Roy, PhD (technical director) and Vanderbilt University Medical Center’s William H. Fissell, MD (medical director).

“We are focused on safely replicating the key functions of a kidney,” said Roy, a bioengineering professor in the UCSF School of Pharmacy. “The bioartificial kidney will make treatment for kidney disease more effective and also much more tolerable and comfortable.”

Inspired by nature, honed by science

Roy and his colleagues engineered the bioreactor to connect directly to blood vessels and veins, allowing the passage of nutrients and oxygen, much like a transplanted kidney would. Silicon membranes keep the kidney cells inside the bioreactor safe from attack by the recipient’s immune cells.

The team used a proximal tubule cell, which regulates water, as a test case. Co-author H. David Humes, MD, from the University of Michigan, had previously used these cells to help dialysis patients in the intensive care unit with life-saving results.

No immunosuppression needed

The team tracked the renal cells and the recipient animals for seven days after transplantation and both did well. The next step will be month-long trials, as required for by the U.S. Food and Drug Administration (FDA), first in animals and eventually in humans.

“We needed to prove that a functional bioreactor will not require immunosuppressant drugs, and we did,” Roy said. “We had no complications and can now iterate up, reaching for the whole panel of kidney functions at the human scale.”

Source: University of California – San Francisco

For Stroke Recovery, Deep Brain Stimulation may Aid Rehabilitation

Deep brain stimulation illustration. Credit: NIH

A first-in-human trial of deep brain stimulation (DBS) for post-stroke rehabilitation patients has shown that using DBS to target the dentate nucleus – which regulates fine-control of voluntary movements, cognition, language, and sensory functions in the brain – is safe and feasible.

The EDEN trial (Electrical Stimulation of the Dentate Nucleus for Upper Extremity Hemiparesis Due to Ischemic Stroke) also shows that the majority of participants (9 of 12) demonstrated improvements in both motor impairment and function. Importantly, the study found that participants with at least minimal preservation of distal motor function at enrolment showed gains that almost tripled their initial scores.

Published in Nature Medicine, these findings build on more than a decade of preclinical work led by principal investigators Andre Machado, MD, PhD, and Kenneth Baker, PhD, at Cleveland Clinic.

“These are reassuring for patients as the participants in the study had been disabled for more than a year and, in some cases, three years after stroke. This gives us a potential opportunity for much needed improvements in rehabilitation in the chronic phases of stroke recovery,” said Dr Machado, patented the DBS method in stroke recovery. “The quality-of-life implications for study participants who responded to therapy have been significant.”

“We saw patients in the study regain levels of function and independence they did not have before enrolling in the research,” Dr Machado said. “This was a smaller study and we look forward to expanding as we have begun the next phase.”

The completed EDEN trial enrolled 12 individuals with chronic, moderate-to-severe hemiparesis of the upper extremity as a result of a unilateral middle cerebral artery stroke 12-to-36 months prior. There were no major complications throughout the study. Nine of the 12 participants improved to a degree that is considered meaningful in stroke rehabilitation.

Source: Cleveland Clinic

‘Digital Bridging’ Enables Paraplegic Man to Walk Again

Study participant Gert-Jan Oskam walking with the brain-spine interface. Credit: Swiss Federal Institute of Technology in Lausanne

A 40 year-old man, Gert-Jan Oskam, has regained the ability to walk independently after being paralysed from a spinal cord injury with the use of a new brain-spine interface. The ‘digital bridging’ technology, developed at the Swiss Federal Institute of Technology in Lausanne and described in Nature, consists of implants and a computer to translate brain signals of the intention to move into stimulations that move the legs accordingly..

This BSI system could be calibrated in minutes, and remained stable for one year, including use at home. The BSI enabled the participant to exert natural control over the movements of his legs to stand, walk, climb stairs and even traverse complex terrains.

In addition to the digital bridging, neurorehabilitation supported by the BSI improved neurological recovery. The participant regained the ability to walk with crutches overground even when the BSI was switched off. This digital bridge establishes a framework to restore natural control of movement after paralysis.

The system consists of a pair cortical of sensors, each an array with 64 electrodes housed in 5cm-diameter titanium discs. These discs are implanted snugly in the skull to pick up brain activity. They transmit the data wirelessly to a personalised headset, which also provides power for the sensors. The headset then sends the data to a portable processing unit (which may be carried in a backpack). Using specialised software, it uses this brain signal data to generates real-time predictions of motor intentions. These decoded intentions are translated into stimulation commands and sent on to another implant, a paddle array of 16 electrodes implanted next to the spinal cord, delivering current to the targeted dorsal root entry zones.

Neurosurgical implantation procedure

Oskam had sustained an incomplete cervical (C5/C6) spinal cord injury during a biking accident 10 years previously. He had already participated in a neurological recovery programme, the STIMO trial, which had used neurostimulation to get him to the stage where he could walk with the aid of a front-wheel walker. The neurorehabilitation from the trial also enabled him to use his hip flexors and lift his legs against gravity, but recovery had plateaued for the three years prior to his participation in the present study.

For the BSI to function, the researchers needed to locate neural features related to the intention to move the legs. To pinpoint the cortical regions associated with the intention to move, they used CT scans and magnetoencephalography. Taking into account anatomical restraints, they then decided on the positions of the implants.

Under general anaesthesia, surgeons performed a bicoronal incision of the scalp to allow two circular-shaped craniotomies over the planned locations of the left and right hemispheres. They then replaced the bone flaps with the two implantable recording devices, before closing the scalp.

The paddle lead had already been emplaced over the dorsal root entry zones of the lumbar spinal cord during the STIMO clinical trial. Its optimal positioning was identified using high-resolution structural imaging of the spine, and its final position was decided during the surgery based on electrophysiological recordings. The implantable pulse generator was inserted subcutaneously in the abdomen. Oskam was able to return home 24 hours after each procedure.