Essential Tremor is the most common form of involuntary movement disorder and is often a debilitating condition for those affected. In the most severe cases, long-term suppression is achieved by chronic thalamic stimulation. Known as deep brain stimulation (DBS), this stimulation uses electrodes implanted in the thalamus which has many parameters with a multitude of possible settings. Improving patient quality of life and tremor reduction requires determination of the optimal patient-specific settings through accurate and precise assessment of tremor severity during stimulator programming.
In our work with the University of Virginia Department of Neurosurgery, we have introduced a technique to provide such assessment of Essential Tremor severity by applying the Teager Energy Function to data collected with a custom, wearable, inertial sensing technology (TEMPO) for continuous, non-invasive, objective measurement of movement disorder such as tremor. This approach affords an opportunity to analyze tremor at a finer level of granularity than is currently possible with the Clinical Rating Scale. This technology facilitates further research of general tremor presentation, treatment, and etiology.
The Teager Energy transform is applied to the vector magnitude of accelerometer signals worn on the hands and head during a clinical visit for stimulator calibration. In addition, the Teager Energy transform has an approximate form that fascilitates use on resource-constrained embedded platforms like those seen in Wireless Health applications.
As seen in the two plots above, our signal processing approach to assessing Essential Tremor provides an intuitive means of evaluating the efficacy of deep brain stimulation on various areas of the body (e.g. right hand, left hand, head) for various intention-inducing postures. Current results obtained from our post-operative pilot study not only serve to quantify tremor severity for programming enhancement, but also reveal axial tremor and ipsilateral benefit – both elusive tremor observations . Efforts are now underway to enable real-time tremor assessment.
Tremor Under Cognitive Load
Parkinson's patients with cognitive impairment may exhibit increased tremor under cognitive load. In this project, we are using TEMPO sensors to monitor subjects' tremor while he or she participates in a series of cognitive exercises.
More information to come.