Knowledge about Essential Tremor: A Study of Essential Tremor Families

Wearable Accelerometer and Gyroscope Sensors for Estimating the Severity of Essential Tremor

BACKGROUND

Several validated clinical scales measure the severity of essential tremor (ET). Their assessments are subjective and can depend on familiarity and training with scoring systems.

METHOD

We propose a multi-modal sensing using a wearable inertial measurement unit for estimating scores on the Fahn-Tolosa-Marin tremor rating scale (FTM) and determine the classification accuracy within the tremor type. 17 ET participants and 18 healthy controls were recruited for the study. Two movement disorder neurologists who were blinded to prior clinical information viewed video recordings and scored the FTM. Participants drew a guided Archimedes spiral while wearing an inertial measurement unit placed at the mid-point between the lateral epicondyle of the humerus and the anatomical snuff box. Acceleration and gyroscope recordings were analyzed. The ratio of the power spectral density between frequency bands 0.5-4 Hz and 4-12 Hz, and the sum of power spectrum density over the entire spectrum of 2-74 Hz, for both accelerometer and gyroscope data, were computed. FTM was estimated using regression model and classification using SVM was validated using the leave-one-out method.

RESULTS

Regression analysis showed a moderate to good correlation when individual features were used, while correlation was high ([Formula: see text] = 0.818) when suitable features of the gyro and accelerometer were combined. The accuracy for two-class classification of the combined features using SVM was 91.42% while for four-class it was 68.57%.

CONCLUSION

Potential applications of this novel wearable sensing method using a wearable Inertial Measurement Unit (IMU) include monitoring of ET and clinical trials of new treatments for the disorder.

Brain Donation Decisions as Disease Specific Behaviors: An Elucidation of the Donation Process in the Context of Essential Tremor

Brain donation is a challenging process, comprising four sequential stages: (1) the brain donation decision, (2) pre-mortem arrangements and follow up, (3) specimen collection and (4) tissue processing. It is important to understand the factors that are pertinent to each stage. Currently, there is extensive information on factors that involve donor’s personal and cultural backgrounds and how these could affect the process. However, little is known about disease-specific factors that influence the process. The Essential Tremor Centralized Brain Repository was established in 2003, and after nearly 20 years of collecting essential tremor (ET) brain tissue, we are well-positioned to discuss the brain donation process from a disease-specific standpoint. In the current manuscript, we discuss ET disease-specific factors that influence the first two stages of the brain donation process. We center our discussion around three points: (1) factors that influence the patient’s decision to donate, (2) the involvement of next of kin in the donation, and (3) the rationale for enrolling patients prospectively and evaluating them longitudinally before the anatomical gift takes place. This discussion shares our understanding of the background from which our repository operates and may be of value for other brain banks that study similar neurodegenerative diseases.

Validity of probands' reports and self-reports of essential tremor: Data from a large family study in North America

The search for genes for essential tremor (ET) is active. Researchers often depend on probands' reports or self-reports to assign disease status to relatives. Yet there are surprisingly few data on the validity of these reports. In two prior studies, with small sample sizes, validity was poor (sensitivity = 16.7-43.3%). In the current study, ET probands and their relatives were screened for tremor and then underwent a videotaped in-person neurological examination. One investigator then assessed the screening questionnaires and videotapes to assign diagnoses of ET, borderline tremor or other diagnosis. There were 98 probands and 243 relatives (105 with ET, 34 with borderline tremor). Educational attainment was high (15.6 ± 2.7 years). Probands failed to report tremor in 39/139 relatives with ET or borderline tremor; conversely, they reported tremor in 32/104 relatives without ET or borderline tremor. Thus, in total, there were 71/243 (29.2%) mis-identifications. Thirty six of 139 ET and borderline ET cases failed to self-report tremor; conversely, 30/104 relatives without ET or borderline tremor self-reported tremor. Thus, in total, there were 66/243 (27.2%) mis-identifications. In summary, in individuals with greater educational attainment, the validity of reported information on ET was considerably higher than previously reported. Despite this, even among well-educated individuals in North America, probands' reports and self-reports misclassified approximately 30% (i.e., one-in-three) of relatives.