Brain Implants
In a development being called the "holy grail of bionics," researchers have made a brain-machine interface device that does not require invasive brain surgery. The stent-based electrode or, stentrode, is implanted within a blood vessel next to the brain, and records neural activity directly.
Medical researchers have created a new minimally invasive brain-machine interface, giving people with spinal cord injuries new hope to walk again with the power of thought. The DARPA funded device consists of a stent-based electrode, or stentrode, which is implanted within a blood vessel next to the brain, and records the type of neural activity that has been shown in pre-clinical trials to move limbs through an exoskeleton or to control bionic limbs.
The new device is the size of a small paperclip and will be implanted in the first in-human trial at The Royal Melbourne Hospital next year.
Traditional electrode arrays are implanted into the brain through a surgical procedure that requires opening the skull, but the stentrode is delivered via catheter angiography, a much lower-risk procedure.
To implant the device a catheter is inserted into a blood vessel in the neck. Researchers then use real-time imaging to guide the stentrode to a precise location in the brain, where the stentrode then expands and attaches to the walls of the blood vessel to read the activity of nearby neurons.
The results published in Nature Biotechnology show the device is capable of recording high-quality signals emitted from the brain’s motor cortex, without the need for open brain surgery.
"We have been able to create the world’s only minimally invasive device that is implanted into a blood vessel in the brain via a simple day procedure, avoiding the need for high risk open brain surgery."
Principal author and Neurologist at The Royal Melbourne Hospital and Research Fellow at The Florey Institute of Neurosciences and the University of Melbourne, Dr Thomas Oxley, said the stentrode was revolutionary.“The development of the stentrode has brought together leaders in medical research from The Royal Melbourne Hospital, The University of Melbourne and the Florey Institute of Neuroscience and Mental Health. In total 39 academic scientists from 16 departments were involved in its development,” Dr Oxley said.
“We have been able to create the world’s only minimally invasive device that is implanted into a blood vessel in the brain via a simple day procedure, avoiding the need for high risk open brain surgery.
“Our vision, through this device, is to return function and mobility to patients with complete paralysis by recording brain activity and converting the acquired signals into electrical commands, which in turn would lead to movement of the limbs through a mobility assist device like an exoskeleton. In essence this a bionic spinal cord.”
Co-principal investigator and biomedical engineer at the University of Melbourne, Dr Nicholas Opie, said the concept was similar to an implantable cardiac pacemaker – electrical interaction with tissue using sensors inserted into a vein, but inside the brain.
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“Utilizing stent technology, our electrode array self-expands to stick to the inside wall of a vein, enabling us to record local brain activity. By extracting the recorded neural signals, we can use these as commands to control wheelchairs, exoskeletons, prosthetic limbs or computers,” Dr Opie said.“In our first-in-human trial, that we anticipate will begin within two years, we are hoping to achieve direct brain control of an exoskeleton for three people with paralysis.”
“Currently, exoskeletons are controlled by manual manipulation of a joystick to switch between the various elements of walking – stand, start, stop, turn. The stentrode will be the first device that enables direct thought control of these devices”
Professor Terry O’Brien, Head of Medicine at Departments of Medicine and Neurology, The Royal Melbourne Hospital and University of Melbourne said the development of the stentrode has been the “holy grail” for research in bionics.
“To be able to create a device that can record brainwave activity over long periods of time, without damaging the brain is an amazing development in modern medicine,” Professor O’Brien said.
“It can also be potentially used in people with a range of diseases aside from spinal cord injury, including epilepsy, Parkinsons and other neurological disorders.”
The study results demonstrate measurement of brain signals with the stentrode that are quantitatively similar to measurements made by commercially available surface electrocorticography arrays implanted during open-brain surgery. Additionally, the study achieved chronic recordings in freely moving sheep for up to 190 days, indicating that implantation of the device could be safe for long-term use.
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