7T MRI features in control human hippocampus and hippocampal sclerosis: An ex vivo study with histologic correlations

Roland Coras, Gloria Milesi, Ileana Zucca, Alfonso Mastropietro, Alessandro Scotti, Matteo Figini, Angelika Mühlebner, Andreas Hess, Wolfgang Graf, Giovanni Tringali, Ingmar Blümcke, Flavio Villani, Giuseppe Didato, Carolina Frassoni, Roberto Spreafico, Rita Garbelli

Research output: Contribution to journalArticlepeer-review


Objective Hippocampal sclerosis (HS) is the major structural brain lesion in patients with temporal lobe epilepsy (TLE). However, its internal anatomic structure remains difficult to recognize at 1.5 or 3 Tesla (T) magnetic resonance imaging (MRI), which allows neither identification of specific pathology patterns nor their proposed value to predict postsurgical outcome, cognitive impairment, or underlying etiologies. We aimed to identify specific HS subtypes in resected surgical TLE samples on 7T MRI by juxtaposition with corresponding histologic sections. Methods Fifteen nonsclerotic and 18 sclerotic hippocampi were studied ex vivo using an experimental 7T MRI scanner. T2-weighted images (T2wi) and diffusion tensor imaging (DTI) data were acquired and validated using a systematic histologic analysis of same specimens along the anterior-posterior axis of the hippocampus. Results In nonsclerotic hippocampi, differences in MR intensity could be assigned to seven clearly recognizable layers and anatomic boundaries as confirmed by histology. All hippocampal subfields could be visualized also in the hippocampal head with three-dimensional imaging and angulated coronal planes. Only four discernible layers were identified in specimens with histopathologically confirmed HS. All sclerotic hippocampi showed a significant atrophy and increased signal intensity along the pyramidal cell layer. Changes in DTI parameters such as an increased mean diffusivity, allowed to distinguish International League Against Epilepsy (ILAE) HS type 1 from type 2. Whereas the increase in T2wi signal intensities could not be attributed to a distinct specific histopathologic substrate, that is, decreased neuronal or increased glial cell densities, intrahippocampal projections and fiber tracts were distorted in HS specimens suggesting a complex disorganization of the cellular composition, fiber networks, as well as its extracellular matrix. Significance Our data further advocate high-resolution MRI as a helpful and promising diagnostic tool for the investigation of hippocampal pathology along the anterior-posterior extent in TLE, as well as in other neurologic and neurodegenerative disorders.

Original languageEnglish
Pages (from-to)2003-2016
Number of pages14
Issue number12
Publication statusPublished - Dec 1 2014


  • Diffusion tensor imaging
  • High resolution 7T MRI
  • Hippocampal sclerosis
  • Hippocampus
  • Neuropathology

ASJC Scopus subject areas

  • Clinical Neurology
  • Neurology
  • Medicine(all)


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