Division of Neurology, Department of Medicine, University of Alberta, 11350 83 Ave NW, Edmonton, AB, T6G 2G3, Canada.
Division of Neurology, Department of Medicine, University of Alberta, 11350 83 Ave NW, Edmonton, AB, T6G 2G3, Canada.
Epilepsy Res. 2020 Mar;161:106279. doi: 10.1016/j.eplepsyres.2020.106279. Epub 2020 Jan 16.
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.
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.
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.
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.
神经病理学研究表明，海马硬化（HS）由三个亚型（ILAE 1-3 型 HS）组成。然而，HS 亚型目前只能通过癫痫手术或尸检中切除的海马组织的病理分析来诊断。HS 亚型的体内诊断有可能提高我们对同侧和对侧海马中这些变体的理解。在这项研究中，我们旨在：i）评估我们的组织学衍生分割方案应用于体内 MRI 的可靠性；ii）描述癫痫患者沿海马长轴的 HS 亚型变异性。
将 11 例单侧 HS 患者与 10 例健康对照进行比较。我们使用 4.7T MRI 对每位患者的海马进行高分辨率 MRI 采集。然后，通过两种方法在每位患者中确定基于体内 MRI 的 HS 亚型诊断：i）整个海马体的海马亚区容积测量；ii）在整个海马体的多个薄片上进行亚区面积分析。
海马体亚区分割显示出极好的可靠性，症状性海马体的容积测量显示所有 11 例患者均存在异常。6 例患者表现出与 1 型 HS 一致的发现，而 5 例患者的症状性海马体有容积定义的非典型 HS（2 例为 2 型 HS，3 例为 3 型 HS），而 5 例患者在对侧海马体中发现 3 型 HS。亚区面积分析表明，在癫痫灶同侧和对侧的海马长轴上，HS 亚型存在显著的变异性。
我们的结果初步证明，使用体内 MRI 确定 HS 亚型可能允许术前诊断 ILAE HS 亚型。进一步的研究对于确定这些神经影像学发现的病理相关性至关重要。沿海马长轴观察到的异常的异质性与之前的尸检研究一致，突出了在这些未来的研究中对癫痫灶同侧和对侧的整个海马进行研究的必要性。
