Open brain surgery is about as dangerous as it sounds, but for sufferers of conditions like Parkinson's and epilepsy it can be the only way to relieve their symptoms. Unfortunately, this means drilling a hole in the skull and stimulating the brain with electrical currents, bringing on the risk of serious side effects. Fortunately, scientists have opened a new doorway to the brain, developing the Stentrode, a promising first-of-a-kind device that can deliver the currents to targeted areas through a small keyhole incision in the neck.

Deep electrical brain stimulation, or DBS, is a hugely promising area of scientific research that could have wide-ranging implications. By applying electrodes to areas of the brain to excite specific neurons, researchers have made very promising advances in everything from slowing the onset of Alzheimer's, to helping paralyzed people feel sensations again, to improving the moods of sufferers of severe depression.

But the process is hugely invasive, requiring scientists to carve out a piece of the skull and inserting wires to deliver the electrical currents to different regions of the brain. Scientists have made some inroads into less invasive techniques that apply currents via the scalp, but a new matchstick-sized device developed at the University of Melbourne is able to enter via a blood vessel instead, opening up a new avenue and a whole host of new possibilities.

"Removing the surgical need for open brain surgery is a huge benefit to patients," Dr Nicholas Opie, a biomechanical engineer who worked on the development of the Stentrode device, explains to New Atlas. "This will significantly reduce their risk of infection, and will reduce the number of days they need to spend in a hospital as our technique is a day procedure. Further, we are not directly touching the brain as the Stentrode is contained and protected within a blood vessel, so the rejection of electrodes that has been reported to occur to penetrating devices has not occurred."

Opie and his team have been working on this technology as a replacement for open brain surgery since 2012. The finished product consists of a microwire and microcatheter that can be inserted via a small hole in the neck and guided through the blood vessel by X-ray until it is in place over the brain's motor cortex. Different electrodes along the length of the Stentrode can then be wirelessly activated to stimulate neurons in different brain regions that correspond with different conditions. As Opie tells us, there were a lot of factors to consider in finalizing the design.

"The primary challenge was to develop a device that could be delivered through a small catheter, around 1 mm, that would then expand to the size of the vessel when deployed," he says. "The device also needed to be made such that the electrodes were as large as possible, could stimulate independent and focused cortical areas, and that they did not restrict blood flow. We are excited that we were able to achieve this."

The researchers have tested the device in a vein running over the motor cortex in sheep, observing its performance compared to electrode arrays placed on the scalp, along with the needle-like electrodes used in current deep brain stimulation. Promisingly, they were able to show that it could activate brain regions that correspond with certain muscle movements in isolation, say a leg or or a lip. But stimulating the brain is only part of the picture.

The Stentrode device also has the ability to monitor electrical signals coming from the brain, creating a two-way communication device that could enable advanced prosthetic devices that can not only touch, but "feel." For example, it could one day help a paralyzed patient use a prosthetic hand to pick up an item and use the feedback to adjust their grip so they don't grasp it too tightly or softly.

"To our knowledge, we are the only team in the world that has been able to demonstrate the ability of recording or stimulating the brain from within a blood vessel using a device suitable for chronic implantation," says Opie. "By having this ability, we could potentially treat a wide range of neurological conditions, including paralysis by recording motor intent and converting these brain signals to computer, wheelchair or exoskeleton control, Parkinson's by supplying stimulation to suppress the tremor, epilepsy by recording from the brain and listening to when a seizure is about to occur and providing stimulation to prevent the occurrence, as well as depression, PTST and OCD. The future possibilities appear to be endless."

Opie says his team has done a "vast mount" of preclinical testing to make sure the device is safe for use in humans, and will conduct their first clinical trials early in 2019, with paralysis earmarked as one of its most promising applications.

"We are excited to learn the extent of what we will be able to get a person with paralysis to control with their mind," he says.

The team's latest research involving testing Stentrode on sheep was published in Nature Biotechnology.

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