Deep brain stimulation (DBS) is a neurosurgical procedure involving a brain pacemaker, which sends electrical impulses, through implanted electrodes, to specific parts of the brain for alleviating various treatment-resistant movement and affective disorders, such as Parkinson’s disease and major depression.
While this procedure has proven to be somewhat effective at assuaging otherwise persistent symptoms, its invasive nature and side effects profile has prompted scientists to look for a way of achieving similar results without the accompanying risks and physical discomfort.
Determined to make a contribution, a team from MIT, led by Polina Anikeeva, an Assistant Professor of Materials Science and Engineering, has recently explored the potential of magnetism to do away with wires and electrodes, typically implanted under the skin of the patient’s chest.
In their study, the researchers injected magnetic iron oxide nanoparticles (just 22 nanometres in diameter) into the brains of mice and subjected them to an external alternating magnetic field, which resulted in the particles rapidly heating up.
The local increase in temperature then leads to neural activation via triggering the heat-sensitive capsaicin receptor TRPV1.
Anikeeva reports that the nanoparticles they used are relatively harmless to the host (they have been used as contrast agents in MRI scans for decades) and can remain dormant in the brain for over a month, allowing for minimally-invasive long-term treatment of chronic symptoms.
“The nanoparticles integrate into the tissue and remain largely intact,” she explained. “Then, that region can be stimulated at will by externally applying an alternating magnetic field. The goal for us was to figure out whether we could deliver stimuli to the nervous system in a wireless and non-invasive way.”
In order to go through with their promising proof-of-concept study, the researchers had to make the particles with precisely controlled shapes and sizes, and develop a device capable of administering the applied magnetic field.
Exciting as they are, the new findings, recently published in Science, need to be replicated and supported by further animal studies to determine potential side effects and appropriate clinical procedures.
“The new method is significant in that it is relatively more easily administered and induces less brain-tissue responses compared to electrode implantation. More importantly, the stimulation could be remotely controlled, a highly appealing feature for deep brain stimulation,” said Bianxiao Cui, a chemistry professor at Stanford University.