Reversible reorganisation of the motor cortical representation of the hand in cervical dystonia

Authors

  • Gary W. Thickbroom PhD,

    Corresponding author
    1. Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Nedlands WA, Australia
    • Brain Research Laboratory, Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands WA 6009, Australia
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  • Michelle L. Byrnes PhD,

    1. Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Nedlands WA, Australia
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  • Rick Stell MB, BS,

    1. Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Nedlands WA, Australia
    2. Department of Neurology and Clinical Neurophysiology, Sir Charles Gairdner Hospital, Nedlands WA, Australia
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  • Frank L. Mastaglia MD

    1. Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Nedlands WA, Australia
    2. Department of Neurology and Clinical Neurophysiology, Sir Charles Gairdner Hospital, Nedlands WA, Australia
    3. Department of Medicine, University of Western Australia, Nedlands WA, Australia
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Abstract

Previous work has suggested that there may be a widespread disturbance of motor control mechanisms in patients with cervical dystonia. In the present study, we used transcranial magnetic stimulation to investigate the topography of the corticomotor projection to the abductor pollicis brevis (APB) muscle in 10 subjects with idiopathic torticollis. Threshold-adjusted stimuli were delivered at multiple scalp sites during a low-level voluntary contraction of the APB, and maps were generated of motor evoked potential amplitude versus scalp site. The cortical maps for the APB on the side opposite to the direction of head rotation were displaced laterally or posteriorly in all subjects and reverted to a more normal position after botulinum toxin injection of the cervical muscles in 5 subjects. The findings point to a reversible reorganisation of the corticomotor representation of the hand on the same side as the sternocleidomastoid (SCM) muscle that is involved in producing the dystonia. These results provide further evidence for the involvement of cortical centres and for a more widespread abnormality of motor control mechanisms in focal dystonia. The findings also support the notion that head turning is chiefly mediated by the hemisphere ipsilateral to the direction of the head rotation by means of a corticomotor projection to the contralateral SCM. © 2003 Movement Disorder Society

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