Impaired motor imagery in patients with essential tremor: A case control study

Authors

  • Yew-Long Lo MD,

    1. Department of Neurology, Singapore General Hospital, Singapore
    2. Department of Neurology, National Neuroscience Institute, Singapore
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  • Elan D. Louis MD, MSc,

    1. G H Sergievsky Center and Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, USA
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  • Stephanie Fook-Chong MSc,

    1. Department of Clinical Research, Singapore General Hospital, Singapore
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  • Eng-King Tan MD, FRCP

    Corresponding author
    1. Department of Neurology, Singapore General Hospital, Singapore
    2. Department of Neurology, National Neuroscience Institute, Singapore
    3. Division of Research, SingHealth, Singapore
    • Movement Disorders Program, Department of Neurology, Singapore General Hospital, Outram Road, Singapore 169608
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Abstract

Motor imagery (MI), which refers to the process of mental representation of movements, has not been studied in patients with essential tremor (ET). We investigated the presence of impaired MI in ET patients compared with healthy controls. A group of drug-naive and nondemented ET patients and age-matched controls were studied using transcranial magnetic stimulation, while they were specifically instructed to try and imagine themselves performing two motor tasks. The various clinical and electrophysiological variables were evaluated and compared. Repeated measures ANOVA demonstrated a significant difference between ET patients and controls with respect to mean motor-evoked potential (MEP) amplitudes (F(1,38) = 31.92, P < 0.005) during MI. The process of MI effectively facilitated MEP amplitude in controls but not in ET patients, regardless of side of stimulation or motor tasks. We provide evidence to demonstrate impairment of MI in a group of ET patients compared with healthy controls. The basis for this novel finding is unclear, and further studies are warranted to determine whether it is related to cerebellar or motor cortical dysfunction. © 2007 Movement Disorder Society

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