Two Teams Report Progress on DBS Alternatives
by James Cavuoto, editor
December 2018 issue
Two different research teams in the U.S. and Australia have recently reported progress in developing alternative forms of brain neuromodulation. The two independent efforts have spawned commercial neurotech startup firms and may eventually impact the market for deep brain stimulation systems.
A team of researchers in Australia recently reported that electrical stimulation can be delivered into the brain from a 4 mm diameter “Stentrode” device permanently implanted inside a blood vessel. Using the Stentrode, neurosurgeons would be able to place electrodes in the brain via blood vessels through a vein in the neck.
The work builds on previous research that showed the Stentrode could be used to record brain signals, with the potential to control an exoskeleton in patients with paralysis. This latest study now shows the Stentrode can also deliver targeted stimulation. The proof-of-concept study was published in Nature Biomedical Engineering and involved researchers from The University of Melbourne, Florey Institute of Neuroscience and Mental Health, The Royal Melbourne Hospital, Monash University, and startup firm Synchron Australia.
The researchers implanted a 4-mm diameter Stentrode into blood vessels in sheep and achieved localized stimulation of brain tissue, all without open-brain surgery. They implanted devices into blood vessels that were adjacent to motor areas of the brain. “Stimulation-induced responses of the facial muscles and limbs were observed, and were comparable with those obtained with electrodes implanted following invasive surgery,” the researchers wrote. “A minimally invasive endovascular surgical approach utilizing a stent-electrode array is an encouraging safe and efficacious way to stimulate focal regions of brain.” Future studies must now determine the safety of stimulation across a range of intensities.
“While additional data is required to validate chronic safety and efficacy of the Stentrode, our previous research, and literature on the success of commercially available cranial stents and vascular lead wires supports our hypothesis that a Stentrode may be a suitable alternative to invasive neural implants,” the researchers said. Lead researcher Nick Opie said the work built on previous research that showed the Stentrode could listen to the motor cortex of the brain. “By adding the ability to speak to the brain using electrical stimulation, we have created a two-way digital communication device,” Opie said. “In one application, the Stentrode could be used as a tool to record the onset of an epileptic seizure, and provide stimulation to prevent it.”
Earlier research, released in 2016, demonstrated that Stentrodes implanted in blood vessels next to the motor cortex could pick up brain signals related to movement. The researchers plan to use the Stentrode to close the loop, making two-way communication with the brain possible. In their upcoming clinical trial, the recording Stentrode will receive and interpret neural signals and enable a person with ALS to control communication software. Eventually it is hoped this technology will be used to help all people suffering from paralysis to control computers, wheelchairs, and exoskeletons.
“From within a blood vessel in the head, the Stentrode can pick up brain signals when people think about moving”, Opie said. “These can be converted into commands that enable direct-brain control of computers, vehicles or prosthetic limbs. With stimulation, sensory feedback is possible, and people may be able to feel what they are touching.”
In another development, a team of neural engineers at the University of California, Berkeley, developed a device that can listen to and stimulate electric current in the brain at the same time. The WAND (wireless artifact-free neuromodulation device) is both wireless and autonomous, meaning that once it learns to recognize the signs of tremor or seizure, it can adjust stimulation parameters on its own to prevent unwanted movements. And because it is closed-loop, it can adjust these parameters in real-time.
“The process of finding the right therapy for a patient is extremely costly and can take years. Significant reduction in both cost and duration can potentially lead to greatly improved outcomes and accessibility,” said Rikky Muller, assistant professor of electrical engineering and computer sciences at Berkeley. “We want to enable the device to figure out what is the best way to stimulate for a given patient to give the best outcomes. And you can only do that by listening and recording the neural signatures.”
WAND can record electrical activity over 128 channels, compared to eight channels in other closed-loop systems. To demonstrate the device, the team used WAND to recognize and delay specific arm movements in rhesus macaques. The device is described in a study published in Nature Biomedical Engineering.
Researchers at Cortera Neurotechnologies, Inc., led by Rikky Muller, designed the WAND custom integrated circuits that can record the full signal from both the subtle brain waves and the strong electrical pulses. This chip design allows WAND to subtract the signal from the electrical pulses, resulting in a clean signal from the brain waves. “Because we can actually stimulate and record in the same brain region, we know exactly what is happening when we are providing a therapy,” Muller said.