Non-thermal focused ultrasound induced reversible reduction of essential tremor in a rat model

Background: Essential tremor (ET) is one of the most common movement disorders of adults, characterized by postural and kinetic tremor. With drug treatment only partially efficient, new treatments are being developed.

Objectives: The goal of this study was to demonstrate the feasibility of non-thermal focused-ultrasound (FUS) to induce tremor-suppression in an ET rat model.

Methods: Harmaline-induced tremor rats were treated with FUS along the inferior olivary (IO) system. EMG was recorded continuously during treatment in order to quantify FUS-induced tremor suppression. T2-weighted MRI was performed immediately following treatment and periodically thereafter.

Results: FUS treatment at an intensity of 27.2 W/cm² (Isppa) induced significant reduction of tremor in 12 out of 13 ET rats. Tremor frequency was reduced from 6.2 ± 2.8 to 2 ± 1 Hz, p < 0.0003. In 6 of the 12 responding rats, tremor was completely suppressed. Response duration was 70 ± 61s, on average. FUS induced motor response, depicted as movement of the tail and/or the limbs synchronized with the FUS sonication, was also demonstrated both in ET rats and in naïve rats when treated in the medulla oblongata region.

Conclusions: These results demonstrate the feasibly for obtaining significant tremor reduction or tremor suppression induced by non-thermal, non-invasive, reversible focused-ultrasound.