Essential Tremor

Essential Tremor (ET) is one of the most common movement disorders, estimated to affect between 1 and 12 million people in the US. It is characterized by a postural and kinetic tremor in the upper limbs, making activities of daily living (eating, clothing, writing, etc.) difficult or impossible. Medication and surgical interventions have significantly reduced patient suffering, but medication only reduces tremor by 50%, and only in 50% of patients, and surgical procedures are generally reserved for severe drug-resistant tremor and have mild to severe side effects, leaving many ET patients without effective treatment options. Surprisingly, assistive and rehabilitative devices are virtually unexplored in this disorder despite success in other neurological disorders involving movement. One might envision, for example, a wearable upper limb device (e.g. an orthosis) with inertia, damping and stiffness specifically designed to suppress (mechanically low-pass filter) tremor in ET patients. However, a significant obstacle to developing effective assistive and rehabilitative devices is that the characteristics of ET are not known throughout the upper limb. Because most studies have only investigated the tremor in a single degree of freedom (most often wrist flexion-extension), we do not know where in the upper limb the tremor manifests most severely, where it originates, and how it propagates, greatly limiting our ability to effectively treat ET with assistive or rehabilitative approaches.

The goal of our work is to:

1. Characterize tremor (in terms of severity and frequency) in all major DOF of the upper limb
2. Apply heuristic and optimization models to the data to establish the mechanical origin of the tremor (i.e. which muscles cause the tremor), and how the tremor propagates from its mechanical origin to other joints of the upper limb
3. Develop devices that suppress tremor in an optimal manner