Electrophysiological features of myoclonus-dystonia

Authors

  • Jie-Yuan Li MD,

    1. Division of Neurology, Department of Medicine and Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada
    2. Division of Neurology, Department of Internal Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
    3. Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
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  • Danny I. Cunic PhD,

    1. Division of Neurology, Department of Medicine and Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada
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  • Guillermo Paradiso MD,

    1. Division of Neurology, Department of Medicine and Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada
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  • Carolyn Gunraj MHSc,

    1. Division of Neurology, Department of Medicine and Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada
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  • Pramod K. Pal MD,

    1. Division of Neurology, Department of Medicine and Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada
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  • Anthony E. Lang MD, FRCPC,

    1. Division of Neurology, Department of Medicine and Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada
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  • Robert Chen MBBChir, MSc, FRCPC

    Corresponding author
    1. Division of Neurology, Department of Medicine and Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada
    • Toronto Western Hospital, 7MC411, 399 Bathurst Street, Toronto, Ontario, Canada M5T 2S8
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  • Potential conflict of interest: None reported.

Abstract

Inherited myoclonus-dystonia (M-D) is an autosomal dominant disorder characterized by myoclonus and dystonia that often improves with alcohol. To examine the electrophysiologic characteristics of M-D, we studied 6 patients from 4 different families and 9 age-matched healthy subjects. Neurophysiological studies performed include electromyography (EMG)-electroencephalography (EEG) polygraphy, jerk-locked back-averaged EEG, somatosensory evoked potentials (SEP), long-latency reflex (LLR) to median and digital nerve stimulation, and transcranial magnetic stimulation studies with short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), and long-interval intracortical inhibition (LICI). All 6 patients showed myoclonus and dystonia on clinical examination and EMG testing. The EMG burst durations ranged from 30.4 to 750.6 milliseconds (mean, 101.5 milliseconds). Jerk-locked back-averaged EEG failed to reveal any preceding cortical correlates. Median nerve SEP revealed no giant potential. No patients had exaggerated LLR to median or digital nerve stimulation. There was no significant difference in SICI, ICF, and LICI between M-D patients and normal subjects. Myoclonus in inherited M-D is likely of subcortical origin. Normal intracortical inhibition and facilitation suggest that the GABAergic circuits in the motor cortex are largely intact and that the mechanisms of myoclonus and dystonia are different from those for cortical myoclonus and other dystonic disorders. © 2008 Movement Disorder Society

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