On the publication of “Closing the Loop in Deep Brain Stimulation: A Responsive Treatment for Essential Tremor,” which was published in the April 19, 2016 edition of Neurology.
ABSTRACT
Objective: to deliver a responsive therapeutic stimulation to patients with Essential Tremor (ET) Background:Essential Tremor (ET) is one of the most common movement disorders defined as a rhythmical, involuntary oscillatory movement of the limbs. Intention tremor occurs in the hands and arms, typically with a slow oscillation (~5-10 Hz). It is experienced during the initiation and execution of goal-directed reaching motions, while it is absent at rest. Although the pathophysiological basis of ET remains unknown, a pathological synchronous oscillation in a neuronal network involving the thalamus, especially the ventral intermediate nucleus (Vim), the premotor (PM) and primary motor (M1) cortices, and the cerebellum has been suggested. Methods: It is assumed that deep brain stimulation (DBS) suppresses tremor by masking the “tremor cells” in the Vim. Stimulation would be delivered on demand based on the presence of specific biomarkers such as movement intention (mu rhythm on motor and premotor cortices), presence of tremor (accelerometer), coherence between electrocorticography (ECoG) and accelerometer. Results: It was possible to detect movement intention within a single trial consistently in the PM and the VIM, showing decrease in low frequency beta oscillations (high beta 18-30 Hz for PM, narrow band high beta 24-27 Hz for VIM) before movement (even in the presence of 105 Hz DBS delivered in the Vim). Conclusions: Using the biomarkers found, it will be theoretically possible to create a closed loop system for ET. This approach would allow theoretically to deliver an equally effective treatment while avoiding most of the stimulation side effects such as balance and speech impairment, and slowing the battery depletion of the implant.