Patients with essential tremor—a neurological disorder that causes involuntary rhythmic shaking during intentional movement—often have difficulty with everyday tasks such as writing, eating, and drinking.
Currently, many patients with essential tremor are treated with Deep Brain Stimulation (DBS), a therapy that requires a surgeon to implant an electrode in the thalamus of a patient’s brain that is wired down the neck to another implanted device—that contains a battery and other electronic components—housed under the clavicle. This type of system, referred to as ‘open-loop,’ delivers constant DBS at levels set by a doctor.
While this DBS system can be effective for patients with essential tremor, the constant stimulation it delivers isn’t necessary and comes with several disadvantages, explained Andrew Ko, M.D., a neurosurgeon and researcher at the University of Washington Medicine Neurosciences Institute.
The symptoms of movement disorders such as Parkinson’s disease or essential tremor do not stay constant,” said Ko in an interview with R&D Magazine. “They can vary throughout the day, with different medication regimens, or even emotional state. Current DBS therapy does not take that into account. Patients may receive more or less stimulation than their symptoms require.”
Involuntary shaking only tends to occur during movement for patients with essential tremor, said Ko. When resting, patients do not have much tremor, which means that the constant stimulation delivered by current DBS devices is unnecessary if someone is relaxed and not performing any tasks.
Too much stimulation can cause side effects, while too little could mean symptoms are not well managed. In addition, extra stimulation uses up battery life unnecessarily. Batteries implanted for DBS only last three to five years before requiring a surgical replacement procedure, so wasting their limited power is not ideal.
A team of electrical engineers, UW Medicine researchers and ethicists at the Center for Sensorimotor Neural Engineering (CSNE) at UW, has developed a novel approach to DBS that solves these issues. Their work is described in a paper to be published in a forthcoming issue of IEEE Transactions on Neural Systems and Rehabilitation Engineering, co-authored by Ko.
Their DBS paradigm uses brain signals to turn the stimulator on and off based on whether a patient requires stimulation at that time. During the implantation surgery, an extra set of electrodes is…