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Membrane dysfunction in Andersen-Tawil syndrome assessed by velocity recovery cycles

Authors

  • S. Veronica Tan MD, FRCP,

    1. MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, United Kingdom
    2. Institute of Neurology, University College London, Queen Square, London WC1N 3BG, United Kingdom
    3. Department of Neurology and Neurophysiology, St Thomas' Hospital, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, United Kingdom
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  • Werner J. Z'Graggen MD,

    1. Clinical Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
    2. Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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  • Delphine BoËrio PhD,

    1. Clinical Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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  • Dipa L. Raja Rayan MA, MRCP,

    1. MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, United Kingdom
    2. Institute of Neurology, University College London, Queen Square, London WC1N 3BG, United Kingdom
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  • Robin Howard PhD, FRCP,

    1. MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, United Kingdom
    2. Institute of Neurology, University College London, Queen Square, London WC1N 3BG, United Kingdom
    3. Department of Neurology and Neurophysiology, St Thomas' Hospital, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, United Kingdom
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  • Michael G. Hanna MD, FRCP,

    1. MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, United Kingdom
    2. Institute of Neurology, University College London, Queen Square, London WC1N 3BG, United Kingdom
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  • Hugh Bostock PhD

    Corresponding author
    1. MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, United Kingdom
    • MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, United Kingdom
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Abstract

Introduction: Andersen-Tawil syndrome (ATS) due to Kir2.1mutations typically manifests as periodic paralysis, cardiac arrhythmias and developmental abnormalities but is often difficult to diagnose clinically. This study was undertaken to determine whether sarcolemmal dysfunction could be identified with muscle velocity recovery cycles (MVRCs). Methods: Eleven genetically confirmed ATS patients and 20 normal controls were studied. MVRCs were recorded with 1, 2, and 5 conditioning stimuli and with single conditioning stimuli during intermittent repetitive stimulation at 20 Hz, in addition to the long exercise test. Results: ATS patients had longer relative refractory periods (P < 0.0001) and less early supernormality, consistent with membrane depolarization. Patients had reduced enhancement of late supernormality with 5 conditioning stimuli (P < 0.0001), and less latency reduction during repetitive stimulation (P < 0.001). Patients were separated completely from controls by combining MVRC and repetitive stimulation. Conclusions: MVRCs combined with repetitive stimulation differentiated ATS patients from controls more effectively than the conventional long-exercise test. Muscle Nerve 46: 193–203, 2012

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