Ultrasound Imaging Triggered Tremor Suppression With Personalized Afferent Stimulation Frequency

Afferent stimulation of peripheral nerves has emerged as a non-invasive approach to suppress wrist tremors in persons with Essential Tremor (ET) and Parkinson' s disease (PD). Electromyography (EMG), a standard sensing modality for tremor characterization during afferent stimulation, has a significant drawback. Due to stimulation artifacts, measuring tremor frequency with EMG and applying stimulation simultaneously is often tricky. This paper investigates a stimulation artifact-free approach that uses real-time ultrasound (US) imaging-derived signals to cue afferent stimulation.

We derived a real-time US imaging-based tissue displacement metric to characterize the wrist tremor in participants with PD or ET. We also compared the metric' s feasibility in detecting the wrist tremor with conventional sensors. We further determined an effective afferent stimulation frequency for each participant that achieved the best tremor suppression. Finally, the metric was evaluated to trigger afferent stimulation (on or off) on the onset or subsidence of the wrist tremor in four participants with PD or ET (two PD, two ET).

Ultrasound imaging can effectively measure the tremor frequency with no significant difference from gold-standard sensors such as EMG and IMU. The US metric-triggered personalized stimulation frequency achieved tremor suppression ratios ranging from 20-73 % in two PD and two ET participants.

These findings indicate that a stimulation artifact-free US-imaging-based metric can simultaneously measure individual tremor characteristics and trigger afferent stimulation.

Our work lays the foundation for new US imaging-based, non-invasive afferent stimulation paradigms for tremor suppression that can potentially benefit more than 11 million people with ET and PD.