Proposal for a magnetic resonance imaging protocol for the detection of epileptogenic lesions at early outpatient stages

Authors

  • Jörg Wellmer,

    Corresponding author
    1. Ruhr-Epileptology, Department of Neurology, University Hospital Knappschaftskrankenhaus, Bochum, Germany
    • Address correspondence to Jörg Wellmer, Ruhr-Epileptology, Department of Neurology, University Hospital Knappschaftskrankenhaus, In der Schornau 23-25, 44892 Bochum, Germany. E-mail: joerg.wellmer@kk-bochum.de

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    • Members of the ad hoc commission “Structural Imaging” of the German Section of the International League Against Epilepsy (ILAE).

  • Carlos M. Quesada,

    1. Department of Epileptology & Life and Brain Institute, University Hospital Bonn, Bonn, Germany
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  • Lars Rothe,

    1. Ruhr-Epileptology, Department of Neurology, University Hospital Knappschaftskrankenhaus, Bochum, Germany
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  • Christian E. Elger,

    1. Department of Epileptology & Life and Brain Institute, University Hospital Bonn, Bonn, Germany
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  • Christian G. Bien,

    1. Epilepsy Center Bethel, Krankenhaus Mara, Bielefeld, Germany
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  • Horst Urbach

    1. Department of Neuroradiology, University Hospital Freiburg, Freiburg, Germany
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    • Members of the ad hoc commission “Structural Imaging” of the German Section of the International League Against Epilepsy (ILAE).


Summary

Purpose

Magnetic resonance imaging (MRI) is a key technology in the presurgical evaluation of patients with epilepsy. Already at early outpatient stages it can contribute to the identification of patients who are, in the case of pharmacoresistance, good candidates for epilepsy surgery. Yet, “standard head” MRI examinations often fail to displaying therapeutically relevant epileptogenic lesions. The purpose of this study is to identify an epilepsy-specific MRI protocol, which is likewise sensitive for even small epileptogenic lesions and economical enough to be applied outside specialized epilepsy centers.

Methods

Based on a large European presurgical epilepsy program comprising 2,740 patients we identified the spectrum of common epileptogenic lesions and determine the set of MRI sequences that are required for their reliable detection. Relying on a series of small, therapeutically particularly relevant lesions we determined the required slices thickness, slice angulations, and orientations for an epilepsy-specific MRI protocol.

Key Findings

Indispensable for early outpatient epilepsy specific MRI are fluid attenuated inversion recovery (FLAIR), T2-weighted, T1-weighted, and hemosiderin/calcification-sensitive sequences. Slice thickness for T2 and FLAIR must not exceed 3 mm. The T1 image should be acquired in three-dimensional technique at 1 mm isotropic voxels size. For T2 and FLAIR, at least two slice orientations each must be demanded in hippocampal angulation. We suggest no adaption to a clinical focus hypothesis. The resulting “essential 6” sequence protocol allows the detection of virtually all common epileptogenic lesion entities.

Significance

The creation of a broadly accepted and abundantly applied MRI protocol for epilepsy outpatients can contribute to improved and earlier identification of potential candidates for epilepsy surgery. Our systematic analysis of MRI requirements for the detection of epileptogenic lesions can serve as basis for protocol negotiations between epileptologists, radiologists, and health care funders.

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