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Neural engineering

DBS implant adapts to patient’s neural signals

10 May 2018 Tami Freeman
Adaptive DBS with fully embedded control
Adaptive DBS with fully embedded control. Top panel: time domain signal recorded from motor cortex; second panel: classifier state (gold), DBS voltage (blue) and gamma power (red).

Scientists in the USA have developed a new deep brain stimulation (DBS) method to treat the symptoms of Parkinson’s disease. While DBS for Parkinson’s is currently delivered continuously, the new approach uses adaptive DBS, in which the stimulation amplitude is modified in real time in response to neural signatures of motor impairment or of stimulation-induced adverse effects.

To test their approach, the researchers trialled adaptive DBS in two patients with Parkinson’s disease, using a fully implanted neural prosthesis enabled to use brain sensing to control stimulation amplitude (J. Neural Eng. 15 046006).

DBS can be an effective treatment for Parkinson’s disease, but it has limitations that reduce efficacy for individual patients and hinder more widespread use of the technique. For example, trained clinicians must programme the implants. It can also be time consuming and, for some patients, satisfactory settings are never achieved.

“This is the first demonstration of adaptive DBS in Parkinson’s disease using a fully implanted device and neural sensing,” said senior author Philip Starr from the University of California, San Francisco. “Our approach uses an algorithm to measure the patient’s neural feedback from the brain surface and change the stimulation in real time. This way, we avoid the stimulation being too intense when it is not needed, which can cause adverse effects such as involuntary movement, known as dyskinesia.”

The device works by using a cortical narrowband gamma oscillation (60-90 Hz) associated with dyskinesia as a control signal. An adaptive DBS algorithm reduces the stimulation voltage when gamma oscillatory activity is high (indicating dyskinesia is likely) and increases the voltage when it is low.

In addition to testing the adaptive DBS system, the researchers also completed an open-loop DBS control session. They observed that, in both patients, the total energy delivered by adaptive stimulation was substantially less than that of open-loop stimulation, while maintaining therapeutic efficacy. The algorithm performed as expected, appropriately detecting changes in gamma band power and triggering voltage reduction when the gamma threshold was exceeded.

“Reducing the stimulation current without losing the therapeutic benefit could reduce stimulation-induced adverse effects. It could also extend battery life, or allow the relatively large pulse generators we currently use to be made smaller,” explained first author Nicole Swann. “Additionally, some of the Parkinson’s disease patients most in need of DBS are also among the most difficult to successfully program: those who alternate between extreme states of dyskinesia and bradykinesia with little in-between time. Adaptive DBS could be very effective for them.”

“This study is a demonstration of the feasibility of adaptive DBS,” said Starr. “Now, further work is needed with a larger-scale trial.”

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