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Finger muscle control in children with dystonia

Authors

  • Scott J. Young PhD,

    1. Department of Biomedical Engineering, University of Southern California, Los Angeles, USA
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  • Johan van Doornik PhD,

    1. Moving Innovations, Enkhuisen, The Netherlands
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  • Terence D. Sanger MD, PhD

    Corresponding author
    1. Departments of Biomedical Engineering, Neurology, and Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, USA
    • Department of Biomedical Engineering, University of Southern California, 1042 Downey Way, DRB 140, Los Angeles, CA 90089-1111

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  • Relevant conflicts of interest/financial disclosures: Nothing to report.

    Full financial disclosures and author roles may be found in the online version of this article.

  • This study was funded by the National Institute of Neurological Disorders and Stroke (NINDS; grant number: NS052236). Additional funding was provided by the Crowley-Carter Foundation and the Don and Linda Carter Foundation.

Abstract

Background: Childhood dystonia is a disorder that involves inappropriate muscle activation during attempts at voluntary movement. Few studies have investigated the muscle activity associated with dystonia in children, and none have done so in the hands.

Methods: In this study, we measured surface electromyographic activity in four intrinsic hand muscles while participants attempted to perform an isometric tracking task using one of the muscles.

Results: Children with dystonia had greater tracking error with the task-related muscle and greater overflow to non-task muscles. Both tracking error and overflow correlated with the Barry-Albright Dystonia scale of the respective upper limb. Overflow also decreased when participants received visual feedback of non-task muscle activity.

Dicussion: We conclude that two of the motor deficits in childhood dystonia—motor overflow and difficulties in actively controlling muscles—can be seen in the surface electromyographic activity of individual muscles during an isometric task. As expected from results in adults, overflow is an important feature of childhood dystonia. However, overflow may be at least partially dependent on an individual's level of awareness of their muscle activity. Most importantly, poor single-muscle tracking shows that children with dystonia have deficits of individual muscle control in addition to overflow or co-contraction. These results provide the first quantitative measures of the muscle activity associated with hand dystonia in children, and they suggest possible directions for control of dystonic symptoms. © 2011 Movement Disorder Society

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