Researchers have, for the first time, showed that it is possible to stimulate structures deep within the brain without the need for implanted electrodes — opening the possibility that epilepsy patients could receive deep brain stimulation in a noninvasive manner.
The method applies scalp electrodes that send two currents into the brain. Brain cells only become stimulated in the spot where the two currents intersect, making it possible to easily change the exact size and location of the treatment.
The Wellcome Trust-funded study, titled “Noninvasive Deep Brain Stimulation via Temporally Interfering Electric Fields,” also suggests noninvasive deep brain stimulation for patients with Parkinson’s disease and certain psychiatric illnesses such as obsessive-compulsive disorder. The work was published in the journal Cell.
“Current deep brain stimulation treatments can only be performed by a small number of neurosurgeons and involve implanting an electrode in the brain which can have complications,” Nir Grossman, a former Wellcome postdoctoral researcher at Massachusetts Institute of Technology (MIT) and the study’s lead author, said in a press release.
To receive deep brain stimulation, an epilepsy patient currently needs to get electrodes implanted near the base of the brain — a procedure linked to a high risk of complications such as bleeding and infections.
“This study shows that it may be possible to noninvasively stimulate deep regions of the brain without harming any surrounding tissue,” said Grossman, who is currently a research fellow at Imperial College London.
Together with colleagues at the Beth Israel Deaconess Medical Center (BIDMC) and the IT’IS Foundation, the team developed a system that takes advantage of a phenomenon called temporal interference.
The scalp electrodes produce two high-frequency currents. The high frequency makes it impossible for the resulting electricity to stimulate neurons, but at the spot the two currents meet, a small region of electrical activity emerges.
Placing the intersection in deep brain regions, researchers could stimulate a chosen region while leaving the surrounding brain tissue completely unaffected.
The system is highly adaptable. By altering the frequency of the two currents and adapting the number and location of the scalp electrodes, researchers can decide the size and exact brain location being stimulated.
When testing the method in mice, they could stimulate deep brain regions as well as trigger movement in the animals’ limbs, ears, or whiskers. The mouse studies could not detect any harmful effects of the stimulation.
“With the ability to stimulate brain structures noninvasively, we hope that we may help discover new targets for treating brain disorders,” Grossman said.
In the release, Dr. Andrew Welchman, head of neuroscience and mental health at Wellcome, spoke about the importance of the study for the development of noninvasive brain treatments.
“This study is exciting as it provides a proof of principle that less invasive methods can be used for deep brain stimulation,” Welchman said. “The concept of delivering stimulation through intersecting electrical ‘beams’ is well established, but this study demonstrates how this technology could be put into practice. It’s an important step forward towards the goal of a noninvasive treatment for patients with serious neurological diseases.”
