Deep brain stimulation (DBS) is a therapy that has been administered to over 100,000 patients worldwide. The majority of people receiving deep brain stimulation live with a diagnosis of Parkinson’s disease (PD). The technique has been helpful for improving tremor, on-off fluctuations, dyskinesia, and off time. One of the main limitations of deep brain stimulation has been that it requires brain surgery and carries an associated risk of hemorrhage, stroke, infection, and hardware failure. Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) have been recently utilized as less robust alternatives, however these therapies have been largely limited to being applied to the brain’s surface and coverings. In this month’s What’s Hot in PD? column we will introduce a deep brain stimulation technique that is not invasive (i.e., no surgery) and can reach deep into the brain.
In this week’s issue of the journal Cell, Ed Boyden and his laboratory at the Massachusetts Institute of Technology introduce a new technique called temporal interference (TI). The novel idea that Ed and his team explored was to deliver multiple currents to the brain at high frequencies (frequency is the number of impulses per second). The idea was to use high frequency as a method to preserve the superficial firing of brain cells (brain cells will ignore the noise if the frequency is high enough). By introducing two current sources at different frequencies and aiming them from outside the brain, the deep interference between the two separated electrical fields can be used to create an envelope. The envelope between the currents would assume a frequency that was the difference between the two current sources. The location of the TI envelope could be adjusted and aimed at specific brain structures. To prove the concept, the MIT-based team stimulated the brains of awake and behaving mice and specifically directed current at the hippocampus (the part of the brain important for memory). The results revealed that Boyden and his team could modulate brain cells in the hippocampus without affecting the superficial brain cells above. This was a remarkable accomplishment.
This clever, non-invasive deep brain stimulation method has the potential to target deep brain circuits without the need for neurosurgery. However, there are several unresolved questions:
- Will the currents delivered be capable of providing the high frequencies necessary to treat many of the most disabling Parkinson’s disease symptoms (depression, tremor, rigidity, bradykinesia, etc.)?
- Can Boyden and colleagues steer the current to the precise regions of the brain that will be necessary to provide sustainable benefit without inducing unacceptable side effects?
- Will the MIT team be able to dream a design to continuously stimulate in a practical, wearable device without the need for a complex superficial surgical implant?
The next steps will certainly include refinement of the technology and eventually testing in humans through carefully designed clinical trials. Though not currently available for human use (for Parkinson’s disease or any other condition), it is possible that at some point in the near future this will be an option for specific Parkinson’s disease-related symptoms.
Nir Grossman, David Bono, Nina Dedic, Li-Huei Tsai, Alvaro Pascual-Leone, Edward S. Boyden. Noninvasive Deep Brain Stimulation via Temporally Interfering Electric Fields. Cell. June 2017 (online before print).
You can find out more about PF's National Medical Director, Dr. Michael S. Okun, by also visiting the Center of Excellence, University of Florida Health Center for Movement Disorders and Neurorestoration. Dr. Okun is also the author of the Amazon #1 Parkinson's Best Seller 10 Secrets to a Happier Life and 10 Breakthrough Therapies for Parkinson's Disease. You can read more from Dr. Okun in the What's Hot in PD? archives.