Objective: To develop an ultrasound (US) image-based model for Essential and Parkinsonian tremor to be used in conjunction with functional electrical stimulation (FES) for tremor suppression.

Background: Essential tremor (ET) and Parkinson disease (PD) are the most common movement disorders, with tremor in both cases rendered medically-refractory within as little as 1 year of initiating available treatments. Deep brain stimulation (DBS) and High Intensity Focused Ultrasound (HIFU) are approved for tremor reduction, but are largely invasive techniques, carrying risk of serious morbidity. In recent history, efforts at peripheral nerve stimulation of a tremulous limb have been investigated and even garnered FDA approval for transient reduction of moderate to severe tremor. However, this technique requires time away from freely using the treated limb while stimulating; with an improvement lasting approximately 90 minutes which leaves patients desiring a more continuous solution. An alternative method for tremor suppression is using FES to stimulate the sensory and motor neurons out of phase of the tremor propagation. This can potentially be achieved through closed-loop control methods which assess the kinematics of tremor and determine the correct stimulation dosage and timing. We hypothesize that US imaging can be utilized in real-time to properly model and assess tremor severity thus leading the way to a translational approach to tremor suppression with FES.

Method: Ultrasound images from 3 groups of subjects (ET, PD, or healthy control) will be collected while performing a grasping motion. Relevant features such as tissue position and velocity will be extracted and compared to additional collected sensor data such as electromyography (EMG) and inertial measurement units (IMU). The relevant ultrasound features will help develop a predictive tremor model.

Results: To date, a preliminary study was performed on 3 participants (1 ET, 1 PD, 1 healthy) and ultrasound features analyses showed marked differences in tremor characteristics between the three groups. We are currently collecting IMU, EMG, and US data on 4 additional participants per group for use in tremor model development.

Conclusion: The preliminary analysis and FES testing shows that US imaging provides important information about tremors on the muscular level and has the potential to be used as a feedback signal in closed-loop FES control.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/analysis-of-tremor-during-grasp-using-ultrasound-imaging/