Influence of electrode site and size on variability of magnetic evoked potentials

Authors

  • Robert J.W. Dunnewold MD,

    1. Department of Neurology and Clinical Neurophysiology, Leiden University Hospital, P.O. Box 9600, 2300 RC Leiden, The Netherlands
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  • Wim van der Kamp MD,

    1. Department of Neurology and Clinical Neurophysiology, Leiden University Hospital, P.O. Box 9600, 2300 RC Leiden, The Netherlands
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  • Antoinette Maassen van den Brink,

    1. Department of Neurology and Clinical Neurophysiology, Leiden University Hospital, P.O. Box 9600, 2300 RC Leiden, The Netherlands
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  • Marion Stijl REEGT,

    1. Department of Neurology and Clinical Neurophysiology, Leiden University Hospital, P.O. Box 9600, 2300 RC Leiden, The Netherlands
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  • J. Gert van Dijk MD, PhD

    Corresponding author
    1. Department of Neurology and Clinical Neurophysiology, Leiden University Hospital, P.O. Box 9600, 2300 RC Leiden, The Netherlands
    • Department of Neurology and Clinical Neurophysiology, Leiden University Hospital, P.O. Box 9600, 2300 RC Leiden, The Netherlands
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Abstract

Successive magnetic evoked potentials (MEPs) concern varying motor neurons. We investigated whether this MEP-specific source of variability depends on electrode site and size. Amplitude variability (standard deviation) was largest over the center of the hypothenar muscles. Latencies were longer at distal and proximal sites than at the center site. Large electrodes (10 cm2) did not decrease this source of amplitude variability compared with EEG electrodes, in contrast to other sources of variability. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21: 1779–1782, 1998

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