Prolonged cortical silent period but normal sensorimotor plasticity in spinocerebellar ataxia 6

Authors

  • James T.H. Teo MA, MRCP, MPhil,

    Corresponding author
    1. Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
    • Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
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  • Susanne A. Schneider MD,

    1. Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
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  • Binith J. Cheeran MRCP, MPhil,

    1. Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
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  • Miguel Fernandez-del-Olmo PhD,

    1. INEF Galicia, Institute of Physical Education and Sport, A Coruña, Spain
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  • Paola Giunti MD, PhD,

    1. Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
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  • John C. Rothwell PhD,

    1. Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
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  • Kailash P. Bhatia MD, DM, FRCP

    1. Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
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Abstract

Spinocerebellar ataxia 6 (SCA6) is a hereditary disease characterized by a trinucleotide repeat expansion in the CACNA1A gene and late-onset bilateral cerebellar atrophy. It is unclear if there is significant pathology outside of the cerebellum. We used transcranial magnetic stimulation to assess sensorimotor cortical circuits and cortical plasticity in 8 SCA6 patients and 8 age-matched controls. Behavioral performance was assessed using a rhythmic tapping task. Neurophysiological measures of SCA6 patients showed a prolonged cortical silent period (CSP) but normal MEP recruitment curve, short-latency afferent inhibition, long-latency afferent inhibition and ipsilateral silent period. Paired-associative stimulation induction also increased motor-evoked potentials normally. SCA6 patients had greater variability with cued rhythmic tapping than normals and deteriorated when the cue was removed; in comparison, normal subjects had similar variability between cued and uncued rhythmic tapping. Analysis using a Wing–Kristofferson timing model indicated that both clock variance and motor delay variance were abnormal. Conclusion. In SCA6, the circuits for sensorimotor integration and the mechanisms for LTP-like plasticity in the sensorimotor cortex are unimpaired. A prolonged CSP in SCA6 just like in other cerebellar atrophies would suggest that this neurophysiological change typifies cerebellar dysfunction. © 2007 Movement Disorder Society

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