Descending control of muscles in patients with cervical dystonia

Authors

  • Marina A.J. Tijssen MD, PhD,

    Corresponding author
    1. Sobell Department of Neurophysiology, The Institute of Neurology, Queen Square, London, United Kingdom
    2. Department of Clinical Neurology, Amsterdam University Medical Centre, Amsterdam, The Netherlands
    • Department of Neurology H2-222, Academic Medical Centre, University of Amsterdam, PO BOX 22660, 1100 DD Amsterdam, The Netherlands
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  • Alex Münchau MD,

    1. Sobell Department of Neurophysiology, The Institute of Neurology, Queen Square, London, United Kingdom
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  • John F. Marsden MSc, MCSP,

    1. Sobell Department of Neurophysiology, The Institute of Neurology, Queen Square, London, United Kingdom
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  • Andrew Lees MD FRCP,

    1. National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom
    2. Reta Lila Weston Institute of Neurological Studies, University College, London, United Kingdom
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  • Kailash P. Bhatia MD, DM,

    1. National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom
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  • Peter Brown MD, FRCP

    1. Sobell Department of Neurophysiology, The Institute of Neurology, Queen Square, London, United Kingdom
    2. National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom
    3. Reta Lila Weston Institute of Neurological Studies, University College, London, United Kingdom
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Abstract

It was reported recently that specific features in the frequency analysis of electromyographic (EMG) activity in the sternocleidomastoid (SCM) and splenius (SPL) muscles were able to distinguish between rotational idiopathic cervical dystonia (CD) and voluntary torticollis in individual subjects. Those with CD showed an abnormal drive to muscles at 5 to 7 Hz and an absence of the normal 10 to 12 Hz peak in the autospectrum of SPL. We sought to determine whether the same abnormalities in the frequency domain are found in complex CD, in which the head is displaced in more than two planes. EMG activity was recorded in the SCM, SPL, trapezius, and levator scapulae muscles bilaterally in 10 patients with complex CD. Frequency analysis of EMG was compared with conventional clinical and polymyographic assessment. The autospectrum of SPL during free dystonic contraction showed an absence of a significant peak at 10 to12 Hz in 8 of the 10 patients. The presence of a 5 to 7 Hz frequency drive showed a significant association with muscle pairs determined as dystonic by means of polymyography (P < 0.005). The neck posture predicted blindly, based on the low-frequency drive, correlated significantly with the clinical assessment of posture (P < 0.01). Conventional assessment and the results of frequency analysis correlated, suggesting that a low-frequency drive to neck muscle may be a general feature of simple rotational and more complex cervical dystonia. The pattern of coherence between the EMG in different neck muscles may provide a means of identifying leading dystonic muscles, especially in patients with complex cervical dystonia. © 2002 Movement Disorder Society

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