UW researchers develop new approach for treating movement disorder

SAN FRANCISCO, July 2 (Xinhua) -- Researchers at the University of Washington (UW) have combined electrodes on top of the brain to sense movement in the parts of the body that experience essential tremor, along with a deep brain electrode, to deliver stimulation only when it's needed.

The approach, developed for the first time by electrical engineers, UW Medicine researchers and ethicists at the Center for Sensorimotor Neural Engineering (CSNE) at UW, is described in a paper to be published in a forthcoming issue of IEEE Transactions on Neural Systems and Rehabilitation Engineering.

Essential tremor is the most common movement disorder, affecting an estimated 7 million people in the United States alone. It triggers an involuntary, rhythmic shaking during intentional movement, complicating everyday tasks like writing, eating and drinking. When resting or sleeping, however, most patients have few or no symptoms.

The disease can be treated with a procedure called Deep Brain Stimulation, or DBS, where a neurosurgeon implants an electrode in the brain; the wire is then tunneled under the skin to a battery in the chest, which provides electrical stimulation that quiets the symptoms. In current use, these devices are constantly "on," delivering stimulation even when a patient doesn't need it.

The electrode in the thalamus of a patient's brain and its wiring with another implanted device housed under the clavicle that contains a battery and the electronics that drive the system is known as an "open-loop" system.

In contrast, what UW researchers have done is a step toward developing fully-implanted, closed-loop deep brain stimulators to treat disorders like essential tremor and Parkinson's disease, devices that one day might be controlled by the patient's own thoughts or movements.

"We'd ultimately like to give individuals that ability and choice," explained co-author Margaret Thompson, a UW electrical engineering doctoral candidate and member of the CSNE team. "One side effect of deep brain stimulation can be difficulty speaking, for instance. So if you're about to drink a glass of water, you might want to turn up the stimulation so your hand doesn't shake. If you're answering the phone, perhaps you'd want to turn it down so your speech isn't affected."

Delivering deep brain stimulation also can extend the battery life of the implanted devices, which currently last only three to five years. Lengthening battery life is important because replacing the battery requires surgery, which carries risks to the patient such as infection.

The project originated in a partnership between the CSNE and medical device manufacturer Medtronic to test new ways of activating Medtronic's Activa PC+S Deep Brain Stimulation system with essential tremor patients. The system not only delivers electrical stimulation like traditional DBS systems, but also has the capability to sense and respond to electrical signals generated by the brain itself.

In three patients who received the Medtronic Activa PC+S Deep Brain Stimulation system, UW Medicine surgeons also implanted a small strip of electrodes on top of the brain's motor cortex, the part of the brain that controls movement. The electrode strip can be used to sense when a hand or other extremity affected by essential tremor is moving. In a key innovation, the team developed machine learning algorithms to "decode" neural signals coming from the brain and correlate them with essential tremor symptoms that warrant treatment by stimulation.

The neural biomarkers and algorithms used to "decode" them differ by disease. While a similar treatment approach has been documented for Parkinson's disease, this is the first time neural signals have been used to selectively treat essential tremor.

Most essential tremor patients have symptoms only during intentional movement, when they move their arm to eat, drink or write, for instance. The UW CSNE closed-loop system detects that movement and only delivers stimulation to quiet the tremor symptoms when needed.

"This is exciting both for treating those patients with essential tremor, but also for future uses," Dr. Jeffrey Ojemann, a CSNE team leader and neurosurgeon with the UW Medicine Neurosciences Institute, was quoted as saying in a news release.

"This represents the first time a person can control their implanted device through the voluntary use of brain signals. We now can see a direct path to all sorts of uses in stroke, paralysis or other neurologic conditions that may be treated in the future using this general approach."