Stentrode- This device could one day help paralysed people move their limbs!
Have you ever imagined that you could walk merely by thinking about walking?
For many paralyzed people, their dream to be up and walking could well become a reality in the near future.
Thanks to a collaboration of 39 brilliant minds from 16 departments across the University of Melbourne’s medicine, science, veterinary science and engineering faculties, this notion of wirelessly thought-controlled limbs is within reach for patients affected with paralysis.
The revolutionary device name “stentrode” is an implantable matchstick-sized device that can read electronic signals from the brain and transmit the signals to an exoskeleton.
Carefully crafted from an alloy material called nitinol, it is designed in such a way that it can undergo compression and expansion without significant loss of function.
It will be inserted into the blood vessel with a catheter fed up through the groin. Once the device is delivered to the motor cortex of the brain, the catheter is removed, deploying the stentrode.
“This technology is really exciting. It’s the first time that we’ve been able to demonstrate and develop a device that can be implanted without the need for a big operation, to chronically record brain activity,” says Terry O’Brien from the Royal Melbourne Hospital and the University of Melbourne’s Medicine, Dentistry and Health Sciences Faculty.
“The most obvious benefit is for people who are paralyzed following a stroke or spinal cord injury. It is simple and non-invasive and much safer for patients.”
Once deployed, the stentrode expands to press the electrodes against the vessel wall close to the brain where it can record neural information and translate these signals into commands that can be used to control an exoskeleton.
“There is no craniotomy, no risk of infection; it’s all run through the groin and passed inside the body up into the brain,” says O’Brien.
“This has been the Holy Grail for research in bionics—a device that can record brainwave activity over long periods. Inside the blood vessel, it’s protected—it doesn’t damage the brain vessel and can stay there forever.”
For the initial trials, Clive May from the Florey Institute of Neuroscience and Mental Health tested the device in sheep.
Upon implantation, the sheep seemed unaffected by the painless and simple operation and were walking and eating within an hour. The signals from the device grew stronger and clearer and reached as high as 190Hz after about 90 days of implantation.
These signals act as the electrical messengers that provoke intricate muscle movements and can, theoretically, be coded into software that links to an external skeleton.
“Personally, the fact that our device can record signals up to 190 hertz is the most exciting finding in our Nature Biotechnology paper,” says Thomas Oxley, a neurologist at the University of Melbourne, who designed the device. “The data between 70 to 200 hertz is the most useful for brain machine interfacing.
“I’ve always been fascinated by the integration of man and machine, and the ways that people and machines could function together. Fortunately, I was born in the time to do this,” says Nick Opie a senior research fellow and co-head of the Vascular Bionics Laboratory at the Royal Melbourne Hospital and the senior engineer behind this device.
He and Oxley co-founded SmartStent, the company that will translate this research into reality.
Dr. Nick Opie was responsible for the design of the stentrode. His challenge was to create a net like device fitted with a electrode that can expand and collapse and more importantly be biocompatible.
“The first iteration was pretty horrible,” he admits. “I don’t want to count how many we’ve made. It required a lot of microscope work and very steady hands.”
Hundreds of iterations later, Dr Opie and his team produced the winning design using a flexible material called nitinol.
It is fitted with tiny recording discs, called electrodes, which sit on the wall of the blood vessel, right next to the brain tissue. Each disc records electrical activity fired by some 10,000 neurons, which is delivered via delicate wires that run out of the brain, into the neck, and emerge into the chest into a wireless transmission system.
These transmitted signals can be coded into signals that control the exoskeleton. However the patients have to ‘code’ these unique signals to their own exoskeleton.
Much like the process of learning to walk or speak again, the process will take many months, until finally, the movement becomes as effortless as driving a car, touch-typing, or writing your name on a form.
The initial trials for the stentrode in patients would begin as early as 2017 wherein the stent will be implanted into carefully selected paraplegic or quadriplegic patients by surgeons at the Royal Melbourne Hospital.
The first patients would most likely be young people who have undergone traumatic spinal cord injury around six months to a year earlier, who are suitable for exoskeleton legs. They will be chosen for their level of determination, their resolve and their physiology, Dr Opie says.
However Dr. Oxley believes that the commercial approval for the device could take as long as seven years and he hopes to bring it to the market by 2022.