Investigation of hippocampal substructures in focal temporal lobe epilepsy with and without hippocampal sclerosis at 7T

Brendan G Santyr; Maged Goubran; Jonathan C Lau; Benjamin Y M Kwan; Fateme Salehi; Donald H Lee; Seyed M Mirsattari; Jorge G Burneo; David A Steven; Andrew G Parrent; Sandrine de Ribaupierre; Robert R Hammond; Terry M Peters; Ali R Khan

doi:10.1002/jmri.25447

Investigation of hippocampal substructures in focal temporal lobe epilepsy with and without hippocampal sclerosis at 7T

J Magn Reson Imaging. 2017 May;45(5):1359-1370. doi: 10.1002/jmri.25447. Epub 2016 Aug 26.

Authors

Brendan G Santyr¹, Maged Goubran^{1

2}, Jonathan C Lau³, Benjamin Y M Kwan^{1

2}, Fateme Salehi^{1

2}, Donald H Lee^{1

2}, Seyed M Mirsattari³, Jorge G Burneo³, David A Steven³, Andrew G Parrent³, Sandrine de Ribaupierre³, Robert R Hammond⁴, Terry M Peters^{1

2}, Ali R Khan^{1

2}

Affiliations

¹ Schulich School of Medicine and Dentistry - Western University, London, Ontario, Canada.
² Departments of Medical Biophysics and Medical Imaging - Western University, London, Ontario, Canada.
³ Department of Clinical Neurological Sciences - London Health Sciences Centre, London, Ontario, Canada.
⁴ Department of Pathology and Laboratory Medicine - London Health Sciences Centre, London, Ontario, Canada.

PMID: 27564217
DOI: 10.1002/jmri.25447

Abstract

Purpose: To provide a more detailed investigation of hippocampal subfields using 7T magnetic resonance imaging (MRI) for the identification of hippocampal sclerosis in temporal lobe epilepsy (TLE).

Materials and methods: Patients (n = 13) with drug-resistant TLE previously identified by conventional imaging as having hippocampal sclerosis (HS) or not (nine without HS, four HS) and 20 age-matched healthy controls were scanned and compared using a 7T MRI protocol. Using a manual segmentation scheme to delineate hippocampal subfields, subfield-specific volume changes and apparent transverse relaxation rate ( R2*) were studied between the two groups. In addition, qualitative assessment at 7T and clinical outcomes were correlated with measured subfield changes.

Results: Volumetry of the hippocampus at 7T in HS patients revealed significant ipsilateral subfield atrophy in CA1 (P = 0.001) and CA4+DG (P < 0.001). Volumetry also uncovered subfield atrophy in 33% of patients without HS, which had not been detected using conventional imaging. R2* was significantly lower in the CA4+DG subfields (P = 0.001) and the whole hippocampus (P = 0.029) of HS patients compared to controls but not significantly lower than the group without HS (P = 0.077, P = 0.109). No correlation was found between quantitative volumetry and qualitative assessment as well as surgical outcomes (Sub, P = 0.495, P = 0.567, P = 0.528; CA1, P = 0.104 ± 0.171, P = 0.273, P = 0.554; CA2+CA3, P = 0.517, P = 0.952, P = 0.130 ± 0.256; CA4+DG, P = 0.052 ± 0.173, P = 0.212, P = 0.124 ± 0.204; WholeHipp, P = 0.187, P = 0.132 ± 0.197, P = 0.628).

Conclusion: These preliminary findings indicate that hippocampal subfield volumetry assessed at 7T is capable of identifying characteristic patterns of hippocampal atrophy in HS patients; however, difficulty remains in using imaging to identify hippocampal pathologies in cases without HS.

Level of evidence: 2 J. MAGN. RESON. IMAGING 2017;45:1359-1370.

Keywords: hippocampal subfields; temporal lobe epilepsy; ultrahigh-field MR; volumetry.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Atrophy / pathology
Case-Control Studies
Epilepsy, Temporal Lobe / diagnostic imaging*
Epilepsy, Temporal Lobe / pathology*
Female
Hippocampus / diagnostic imaging*
Hippocampus / pathology*
Humans
Image Processing, Computer-Assisted
Magnetic Resonance Imaging*
Male
Middle Aged
Sclerosis
Treatment Outcome
Young Adult

Grants and funding

CIHR/Canada