This method can be used to characterize the distribution of tremor throughout the upper limb. Our preliminary characterization suggests that the amount of tremor increases in a proximal-distal manner.

Tremor is the most common movement deficit and manifests in a variety of disorders, including Essential Tremor, Parkinson's Disease, Dystonia, and Cerebellar Ataxia. Although medication and surgical interventions have significantly reduced patient suffering, they are only partially effective and can carry undesired side effects, leaving many patients without satisfactory treatment options. Wearable tremor-suppressing devices could provide an alternative to medication and surgery. Multiple research groups have developed orthotic prototypes to low-pass filter tremor, but these devices have not yet been optimized for in-vivo use. Optimizing non-invasive tremor suppression requires an understanding of where the tremor originates mechanically (which muscles) and how it propagates to the hand (where it matters most). Here we present on the beginnings of our multi-pronged work to determine the origin, propagation, and distribution of Essential Tremor, and we provide preliminary results.

Electromagnetic (EM) motion tracking systems are suitable for many research and clinical applications, including in vivo measurements of whole-arm movements. Unfortunately, the methodology for in vivo measurements of whole-arm movements using EM sensors is not well described in the literature, making it difficult to perform new measurements and all but impossible to make meaningful comparisons between studies. The recommendations of the International Society of Biomechanics (ISB) have provided a great service, but by necessity they do not provide clear guidance or standardization on all required steps. The goal of this paper was to provide a comprehensive methodology for using EM sensors to measure whole-arm movements in vivo. We selected methodological details from past studies that were compatible with the ISB recommendations and suitable for measuring whole-arm movements using EM sensors, filling in gaps with recommendations from our own past experiments. The presented methodology includes recommendations for defining coordinate systems (CSs) and joint angles, placing sensors, performing sensor-to-body calibration, calculating rotation matrices from sensor data, and extracting unique joint angles from rotation matrices. We present this process, including all equations, for both the right and left upper limbs, models with nine or seven degrees-of-freedom (DOF), and two different calibration methods. Providing a detailed methodology for the entire process in one location promotes replicability of studies by allowing researchers to clearly define their experimental methods. It is hoped that this paper will simplify new investigations of whole-arm movement using EM sensors and facilitate comparison between studies.

Introduction The patient was a 72-year-old man with a history of hypertension, hyperlipidemia, benign prostatic hyperplasia, and oropharyngeal cancer. His home medications include amlodipine, atorvastatin, hydrochlorothiazide, and tamsulosin. He lives alone and eats a soft, bland, nutrient-poor diet. During his annual primary care visit, he is found to have a serum potassium level of 3.3 mEq/L (reference range 3.5-5.0). Assessment The use of hydrochlorothiazide, a thiazide diuretic, as well as his low consumption of dietary potassium, have likely contributed to his mild, asymptomatic hypokalemia. Outcome The patient’s serum potassium normalizes following replenishment with a 10 mEq microencapsulated potassium chloride (KCl) extended release (ER) tablet three times a day with meals for one week. A registered dietitian was consulted to provide recommendations for a well-balanced diet, consistent with his dietary texture needs. Conclusions Hypokalemia is a commonly encountered electrolyte disorder, occurring in about 3 to 4% of community-dwelling elders.1 Though asymptomatic hypokalemia is often an incidental finding, it is associated with an increased risk of major adverse cardiovascular events if left untreated and thus should be promptly corrected when discovered.2