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      A digital assessment system for evaluating kinetic tremor in essential tremor and Parkinson’s disease

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          Abstract

          Background

          Spiral drawing on papers is a common tremor evaluation tool for diagnosing patients with essential tremor (ET) or Parkinson’s disease (PD). No standard drawing methods and parameters that use graphic tablets are yet available for objective evaluation.

          Methods

          This study established a tremor assessment system for tremor severity by using graphic tablets. Twelve patients with ET and twelve patients with PD were tested to establish system algorithms, and six additional patients were tested with the developed system to evaluate its performance. The patients also performed spiral drawing with three guiding paradigms on a graphic tablet: traced along a given spiral (S1), performed freehand drawing (S2), and traced along a guiding point (S3). Three parameters were calculated to quantify tremor severity: the means of radial difference per radian ( |dr/dθ |), the means of radial difference per second ( |dr/dt |), and the area under curve (AUC) of the frequency spectrum of the velocity. Each patient’s drawing was also evaluated using a visual rating scale (VRS) by experienced physicians. The interrater reliability was examined to identify the most consistent test paradigm.

          Results

          The parameter |dr/dθ | and AUC correlated well with the VRS ( R > 0.8) in S1, S2 and S3 tests. The S1 test presented the best interrater reliability (Weighted Kappa coefficient, k = 0.80) among three tests. The Weighted Kappa coefficients are 0.67 and 0.71 in S2 and S3 tests, respectively.

          Conclusions

          We developed three different guiding paradigms for spiral drawing on a digital graphic tablet for clinical tests. Three parameters were calculated to represent the tremor severity in spiral drawing and used to quantify temporal and spatial characteristics of tremor, and provided good correlation with current clinical assessments. The test “traced along a given spiral” is recommended due to its good interrater reliability.

          Electronic supplementary material

          The online version of this article (10.1186/s12883-018-1027-2) contains supplementary material, which is available to authorized users.

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          Most cited references14

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          Tremor amplitude is logarithmically related to 4- and 5-point tremor rating scales.

          Tremor rating scales (TRSs) are used commonly in the clinical assessment of tremor, but the relationship of a TRS to actual tremor amplitude has never been quantified. Consequently, the resolution of these scales is unknown, and the clinical significance of a 1-point change in TRS is uncertain. We therefore sought to determine the change in tremor amplitude that corresponds to a 1-point change in a typical 5-point TRS. Data from five laboratories were analysed, and 928 patients with various types of hand tremor were studied. Hand tremor was quantified with a graphics tablet in three different labs, an accelerometer in three labs and a mechanical-linkage device in one lab. Tremor in writing, drawing, horizontal posture, rest and finger-nose testing was graded using a variety of TRSs. The relationship between TRS scores and tremor amplitude was computed for each task and laboratory. A logarithmic relationship between a 5-point (0-4) TRS and tremor amplitude (T, measured in centimetres) was found in all five labs, despite widely varying rating scales and transducer methodology. Thus, T2/T1 = 10(alpha(TRS2-TRS1)). The value of alpha ranged from 0.414 to 0.441 for writing, 0.355-0.574 for spiral drawing, 0.441 to 0.488 for rest tremor, 0.266-0.577 for postural tremor and 0.306 for finger-nose testing. For alpha = 0.3, 0.4, 0.5, 0.6 and 0.7, the ratios T2/T1 for a 1-point decrease in TRS are 0.501, 0.398, 0.316, 0.251 and 0.200. Therefore, a 1-point change in TRS represents a substantial change in tremor amplitude. Knowledge of the relationship between TRS and precise measures of tremor is useful in interpreting the clinical significance of changes in TRS produced by disease or therapy.
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            Validation of digital spiral analysis as outcome parameter for clinical trials in essential tremor.

            Essential tremor, one of the most prevalent movement disorders, is characterized by kinetic and postural tremor affecting activities of daily living. Spiral drawing is commonly used to visually rate tremor intensity, as part of the routine clinical assessment of tremor and as a tool in clinical trials. We present a strategy to quantify tremor severity from spirals drawn on a digitizing tablet. We validate our method against a well-established visual spiral rating method and compare both methods on their capacity to capture a therapeutic effect, as defined by the change in clinical essential tremor rating scale after an ethanol challenge. Fifty-four Archimedes spirals were drawn using a digitizing tablet by nine ethanol-responsive patients with essential tremor before and at five consecutive time points after the administration of ethanol in a standardized treatment intervention. Quantitative spiral tremor severity was estimated from the velocity tremor peak amplitude after numerical derivation and Fourier transformation of pen-tip positions. In randomly ordered sets, spirals were scored by seven trained raters, using Bain and Findley's 0 to 10 rating scale. Computerized scores correlated with visual ratings (P < 0.0001). The correlation was significant at each time point before and after ethanol (P < 0.005). Quantitative ratings provided better sensitivity than visual rating to capture the effects of an ethanol challenge (P < 0.05). Using a standardized treatment approach, we were able to demonstrate that spirography time-series analysis is a valid, reliable method to document tremor intensity and a more sensitive measure for small effects than currently available visual spiral rating methods. Copyright © 2011 Movement Disorder Society.
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              Neurological Tremor: Sensors, Signal Processing and Emerging Applications

              Neurological tremor is the most common movement disorder, affecting more than 4% of elderly people. Tremor is a non linear and non stationary phenomenon, which is increasingly recognized. The issue of selection of sensors is central in the characterization of tremor. This paper reviews the state-of-the-art instrumentation and methods of signal processing for tremor occurring in humans. We describe the advantages and disadvantages of the most commonly used sensors, as well as the emerging wearable sensors being developed to assess tremor instantaneously. We discuss the current limitations and the future applications such as the integration of tremor sensors in BCIs (brain-computer interfaces) and the need for sensor fusion approaches for wearable solutions.
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                Author and article information

                Contributors
                bogalin@gmail.com
                stanleychen1230@gmail.com
                +886-3-5731741 , bsyang@mail.nctu.edu.tw
                allen930387@gmail.com
                Journal
                BMC Neurol
                BMC Neurol
                BMC Neurology
                BioMed Central (London )
                1471-2377
                9 March 2018
                9 March 2018
                2018
                : 18
                : 25
                Affiliations
                [1 ]ISNI 0000 0001 2059 7017, GRID grid.260539.b, Department of Mechanical Engineering, , National Chiao Tung University, ; 1001 University Road, Hsinchu City, 30010 Taiwan
                [2 ]ISNI 0000 0004 0572 7815, GRID grid.412094.a, Neurology Division, , National Taiwan University Hospital, Hsinchu Branch, ; Hsinchu City, 300 Taiwan
                [3 ]ISNI 0000 0001 2059 7017, GRID grid.260539.b, Institute of Biomedical Engineering, , National Chiao Tung University, ; Hsinchu City, 300 Taiwan
                Article
                1027
                10.1186/s12883-018-1027-2
                5845296
                29523097
                a86a05fd-d261-40bd-8670-333c2d628514
                © The Author(s). 2018

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                : 24 October 2017
                : 28 February 2018
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100004663, Ministry of Science and Technology, Taiwan;
                Award ID: MOST 105-2628-E-009-003-MY3
                Award Recipient :
                Funded by: National Chiao Tung University (TW) and National Taiwan University Hospital Hsin-chu Branch collaborative project
                Award ID: 104W970 & 105W970
                Award Recipient :
                Categories
                Research Article
                Custom metadata
                © The Author(s) 2018

                Neurology
                essential tremor,parkinson’s disease,spiral drawing,clinical assessment
                Neurology
                essential tremor, parkinson’s disease, spiral drawing, clinical assessment

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