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Seven-Tesla MRI of Hippocampal Sclerosis: An In Vivo Feasibility Study With Histological Correlations

Stefanits, Harald MD*; Springer, Elisabeth MD; Pataraia, Ekaterina MD; Baumgartner, Christoph MD§; Hainfellner, Johannes A. MD; Prayer, Daniela MD; Weisstanner, Christian MD#; Czech, Thomas MD*; Trattnig, Siegfried MD

doi: 10.1097/RLI.0000000000000388
Original Articles
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Introduction Temporal lobe epilepsy (TLE) is the most frequent form of focal epilepsy in adults. Because approximately half of these patients develop drug resistance, epilepsy surgery designed to remove the epileptogenic zone is an excellent option in selected patients. Histopathological analyses of hippocampal specimens in TLE patients revealed 4 types of Ammon's horn sclerosis, which are correlated with long-term epileptological outcome. The aim of this study was the correlation of noninvasive, high-resolution, morphological magnetic resonance imaging (MRI) at an ultra-high-field (7 T) of the hippocampus in TLE patients with histopathological findings.

Methods High-resolution, T2-weighted FSE MRI in 14 patients with drug-resistant temporal lobe epilepsy was performed on a 7 T Magnetom using a 32-channel coil. Four independent investigators assessed the delineation and semiquantitative evaluation of volume, signal intensity, internal architecture, and overall grading of the hippocampal subfields CA1-4, as well as the presence of the dentate granule cell layer (DGCL), on MRI scans. Results were compared with semiquantitative evaluation of neuronal loss and astrogliosis in the histological sections of the surgical specimens.

Results Seven-tesla MR examinations were evaluable in 13 cases. Volume loss and signal intensity, as well as overall grading, showed a strong correlation between MRI and histology in individual CA regions. Furthermore, sensitivity and specificity values up to 100% were found for the detection of pathology in the CA subfields. The prediction of Ammon's horn sclerosis type was correct in up to 12 of 13 cases, whereas the dentate gyrus could not be delineated on MRI.

Discussion High-resolution, ultra-high-field MRI is a promising tool for the detection of subtle changes in the hippocampus in patients with temporal lobe epilepsy. Large cohorts will be necessary to confirm the predictive value of 7 T MRI in the preoperative evaluation of TLE patients.

From the *Department of Neurosurgery, Medical University of Vienna; †High-Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna and Christian Doppler Laboratory for Clinical Molecular MR Imaging; ‡Department of Clinical Neurology, Medical University of Vienna; §Department of Neurology, General Hospital Hietzing with Neurological Center Rosenhuegel; ∥Institute of Neurology, Medical University of Vienna; ¶Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Austria; and #University Institute for Diagnostic and Interventional Neuroradiology, University Hospital Bern and Inselspital, University of Bern, Bern, Switzerland.

Received for publication March 23, 2017; and accepted for publication, after revision, April 18, 2017.

Conflicts of interest and sources of funding: none declared.

Correspondence to: Siegfried Trattnig, MD, High-Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna and Christian Doppler Laboratory for Clinical Molecular MR Imaging, Waehringer Guertel 18-20, A-1090 Vienna, Austria. E-mail: siegfried.trattnig@meduniwien.ac.at.

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