Using the Accelerometers Integrated in Smartphones to Evaluate Essential Tremor

Abstract

Background/Aims: Evaluation of tremor constitutes a crucial step from the diagnosis to the initial treatment and follow-up of patients with essential tremor. The severity of tremor can be evaluated using clinical rating scales, accelerometry, or electrophysiology. Clinical scores are subjectively given, may be affected by intra- and interevaluator variations due to different experience, delays between consultations, and subtle changes in tremor severity. Existing medical devices are not routinely used: they are expensive, time-consuming, not easily accessible. We aimed at showing that a smartphone application using the accelerometers embedded in smartphones is effective for quantifying the tremor of patients presenting with essential tremor. Methods: We developed a free iPhone/iPod application, Itremor, and evaluated different parameters on 8 patients receiving deep brain stimulation of the ventral intermediate nucleus of the thalamus: average and maximum accelerations, time above 1 g of acceleration, peak frequency, typical magnitude of tremor, for postural and action tremors, on and off stimulation. Results: We demonstrated good correlations between the parameters measured with Itremor and clinical score in all conditions. Itremor evaluation enabled higher discriminatory power and degree of reproducibility than clinical scores. Conclusion: Itremor can be used for routine objective evaluation of essential tremor, and may facilitate adjustment of the treatment.

Intraoperative acceleration measurements to quantify improvement in tremor during deep brain stimulation surgery

“…Accelerometers have been applied outside the operating room (OR) for a wide variety of purposes, e.g., to characterize pathological tremor [8,13], to compare it with physiological tremor [20,35,36], and to evaluate the severity and evolution of tremor [28,29,40] and the tremor-alleviating effect of drugs or DBS [22,36,47]. Pulliam et al [34] used motion sensors during postoperative DBS pulse generator programming to develop automated programming algorithms and concluded that objective assessment can improve patients' outcomes.…”

Assessment of Head Tremor with Accelerometers Versus Gyroscopic Transducers

“…Accelerometers and gyroscopes are used commonly in the assessment of hand tremor, but there are only a few published studies in which accelerometry was used to assess head tremor and no reports in which gyroscopes were used. In general, body motion has six degrees of freedom: three‐dimensional (3D) translation and 3D rotation.…”

TREMOR12: An Open-Source Mobile App for Tremor Quantification

“…The Georgia Tech Research Institute developed iTrem, but regulatory issues by the Food and Drug Administration (FDA) prevent the release of the app [13]. Senova et al [4] reported on Itremor, which also does not provide researchers with the raw data, but instead with a few calculated statistics (like acceleration, frequency, and magnitude). The app is only available from Ad Hoc distribution, not from the App Store.…”

“…Quantitative features can be extracted from the motion sensors on the device and used to develop mathematical models for predicting rating scores from kinematic data [3]. Accelerometers integrated in smartphones or wrist-worn devices can also be used for this purpose [4], which lowers the threshold for tremor quantification during activities of daily living.…”