Effect of epilepsy magnetic source imaging on intracranial electrode placement

Authors

  • Robert C. Knowlton MD, MSPH,

    Corresponding author
    1. University of Alabama at Birmingham Epilepsy Center, Department of Neurology, University of Alabama at Birmingham, School of Medicine
    • UAB Epilepsy Center, 312 Civitan International Research Center, 1719 6th Avenue South, Birmingham, AL 35294-0001
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  • Shantanu N. Razdan MBBS,

    1. University of Alabama at Birmingham School of Public Health, University of Alabama at Birmingham; Birmingham, AL
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  • Nita Limdi PhD, MSPH,

    1. University of Alabama at Birmingham Epilepsy Center, Department of Neurology, University of Alabama at Birmingham, School of Medicine
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  • Rotem A. Elgavish MD, PhD,

    1. University of Alabama at Birmingham Epilepsy Center, Department of Neurology, University of Alabama at Birmingham, School of Medicine
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  • Jeff Killen RT(MR),

    1. University of Alabama at Birmingham Epilepsy Center, Department of Neurology, University of Alabama at Birmingham, School of Medicine
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  • Jeffrey Blount MD,

    1. Epilepsy Programme, Department of Clinical Neurological Sciences, University of Western Ontario, London, Ontario, Canada
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  • Jorge G. Burneo MD, MSPH,

    1. Division of Pediatric Neurology, Department of Pediatrics, University of Alabama at Birmingham School of Medicine; Birmingham, AL
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  • Lawrence Ver Hoef MD,

    1. University of Alabama at Birmingham Epilepsy Center, Department of Neurology, University of Alabama at Birmingham, School of Medicine
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  • Lebron Paige MD,

    1. University of Alabama at Birmingham Epilepsy Center, Department of Neurology, University of Alabama at Birmingham, School of Medicine
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  • Edward Faught MD,

    1. University of Alabama at Birmingham Epilepsy Center, Department of Neurology, University of Alabama at Birmingham, School of Medicine
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  • Pongkiat Kankirawatana MD,

    1. Division of Pediatric Neurology, Department of Pediatrics, University of Alabama at Birmingham School of Medicine; Birmingham, AL
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  • Al Bartolucci PhD,

    1. University of Alabama at Birmingham School of Public Health, University of Alabama at Birmingham; Birmingham, AL
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  • Kristen Riley MD,

    1. Division of Neurosurgery, Department of Surgery, University of Alabama at Birmingham School of Medicine; Birmingham, AL
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  • Ruben Kuzniecky MD

    1. New York University Comprehensive Epilepsy Center, New York University Medical School, New York, NY
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  • Potential conflict of interest: Nothing to report.

Abstract

Objective

Intracranial electroencephalography (ICEEG) with chronically implanted electrodes is a costly invasive diagnostic procedure that remains necessary for a large proportion of patients who undergo evaluation for epilepsy surgery. This study was designed to evaluate whether magnetic source imaging (MSI), a noninvasive test based on magnetoencephalography source localization, can supplement ICEEG by affecting electrode placement to improve sampling of the seizure onset zone(s).

Methods

Of 298 consecutive epilepsy surgery candidates (between 2001 and 2006), 160 patients were prospectively enrolled by insufficient localization from seizure monitoring and magnetic resonance imaging results. Before presenting MSI results, decisions were made whether to proceed with ICEEG, and if so, where to place electrodes such that the hypothetical seizure-onset zone would be sampled. MSI results were then provided with allowance of changes to the original plan.

Results

MSI indicated additional electrode coverage in 18 of 77 (23%) ICEEG cases. In 39% (95% confidence interval, 16.4–61.4), seizure-onset ICEEG patterns involved the additional electrodes indicated by MSI. Sixty-two patients underwent surgical resection based on ICEEG recording of seizures. Highly localized MSI was significantly associated with seizure-free outcome (mean, 3.4 years; minimum, >1 year) for the entire surgical population (n = 62).

Interpretation

MSI spike localization increases the chance that the seizure-onset zone is sampled when patients undergo ICEEG for presurgical epilepsy evaluations. The clinical impact of this effect, improving diagnostic yield of ICEEG, should be considered in surgery candidates who do not have satisfactory indication of epilepsy localization from seizure semiology, electroencephalogram, and magnetic resonance imaging. Ann Neurol 2009;65:716–723

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