Related Experiment Video
Updated: Dec 27, 2025
High-resolution In Vivo Manual Segmentation Protocol for Human Hippocampal Subfields Using 3T Magnetic Resonance Imaging
Published on: November 10, 2015
Hippocampal subfield measurement and ILAE hippocampal sclerosis subtype classification with in vivo 4.7 tesla MRI
Trevor A Steve1, Justine Gargula1, Ehsan Misaghi1
1Division of Neurology, Department of Medicine, University of Alberta, 11350 83 Ave NW, Edmonton, AB, T6G 2G3, Canada.
Insights
This study shows that in vivo MRI can reliably diagnose hippocampal sclerosis (HS) subtypes, revealing variability along the hippocampus. This may enable preoperative diagnosis of ILAE HS subtypes.
Area of Science:
- Neuroimaging
- Epilepsy Research
- Pathology
Background:
- Hippocampal sclerosis (HS) has three subtypes (ILAE types 1-3), currently diagnosed via post-surgical or autopsy tissue analysis.
- In vivo diagnosis of HS subtypes could enhance understanding of hippocampal variants.
Purpose of the Study:
- To assess the reliability of a histology-derived segmentation protocol for in vivo MRI.
- To characterize HS subtype variability along the hippocampal long axis in epilepsy patients.
Main Methods:
- Compared 11 unilateral HS subjects with 10 healthy controls using 4.7 T MRI.
- Determined in vivo HS subtypes via hippocampal subfield volumetry and subfield area analysis.
Main Results:
- Segmentation showed excellent reliability; volumetry identified abnormalities in all HS patients.
- Six patients had type 1 HS; five had atypical HS (types 2 or 3) in the symptomatic hippocampus.
- Five patients showed type 3 HS in the contralateral hippocampus; variability was noted along the hippocampal axis.
Conclusions:
- In vivo MRI shows potential for preoperative diagnosis of ILAE HS subtypes.
- Observed heterogeneity along the hippocampal axis aligns with autopsy findings.
- Further research is needed to correlate neuroimaging findings with pathological correlates.
Objective:
Neuropathological studies indicate that hippocampal sclerosis (HS) consists of three subtypes (ILAE types 1-3 HS). However, HS subtypes currently can only be diagnosed by pathological analysis of hippocampal tissue resected during epilepsy surgery or at autopsy. In vivo diagnosis of HS subtypes holds potential to improve our understanding of these variants in the ipsilateral as well as contralateral hippocampus. In this study, we aimed to: i) evaluate the reliability of our histology-derived segmentation protocol when applied to in vivo MRI; and ii) characterize variability of HS subtypes along the hippocampal long axis in patients with epilepsy.
Methods:
Eleven subjects with unilateral HS were compared with ten healthy controls. We used 4.7 T MRI to acquire high resolution MR Images of the hippocampus in each subject. In vivo MRI-based diagnoses of HS subtypes were then determined in each patient by two methods: i) hippocampal subfield volumetry of the entire hippocampal body; and ii) subfield area analysis at multiple thin slices throughout the hippocampal body.
Results:
Hippocampal body subfield segmentation demonstrated excellent reliability and volumetry of the symptomatic hippocampus revealed abnormalities in all eleven patients. Six subjects demonstrated findings consistent with type 1 HS while five subjects had volumetry-defined atypical HS (two with type 2 HS & three with type 3 HS) in the symptomatic hippocampus, while five subjects were found to have type 3 HS in the contralateral hippocampus. Subfield area analyses demonstrated remarkable variability of HS subtypes along the hippocampal long axis, both ipsilateral and contralateral to the seizure focus.
Significance:
Our results provide preliminary evidence that determining HS Subtype using in vivo MRI may allow preoperative diagnosis of ILAE HS subtypes. Further studies are essential to determine the pathological correlates of these neuroimaging findings. The heterogeneity of abnormalities observed along the long axis of the hippocampus is consistent with previous autopsy studies and highlights the necessity of studying the entire hippocampus both ipsilateral and contralateral to the seizure focus in these future studies.
