Clinical Epileptology and Experimental Neurophysiology Unit, IRCCS Foundation Neurological Institute "C. Besta,", Milan, Italy; Department of Neuropathology, University Hospital Erlangen, Germany.
Epilepsia. 2014 Dec;55(12):2003-16. doi: 10.1111/epi.12828. Epub 2014 Nov 3.
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.
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.
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.
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.
海马硬化（HS）是颞叶癫痫（TLE）患者的主要结构性脑损伤。然而，在 1.5 或 3T 磁共振成像（MRI）下，其内部解剖结构仍然难以识别，这既无法识别特定的病理模式，也无法预测其对术后结果、认知障碍或潜在病因的价值。我们旨在通过与相应的组织学切片对比，在 7T MRI 上识别切除的 TLE 样本中的特定 HS 亚型。
对 15 例非硬化和 18 例硬化的海马进行离体研究，使用实验性 7T MRI 扫描仪。获取 T2 加权图像（T2wi）和弥散张量成像（DTI）数据，并通过对海马前-后轴上相同标本的系统组织学分析进行验证。
在非硬化的海马中，MR 强度的差异可以分配给七个可识别的层和解剖边界，这一点通过组织学得到了证实。通过三维成像和斜冠状平面，也可以在海马头部观察到所有海马亚区。在经组织病理学证实为 HS 的标本中，只识别出四个可辨别的层。所有硬化的海马均表现出明显的萎缩和沿锥体细胞层的信号强度增加。DTI 参数的变化，如平均弥散度的增加，允许将国际抗癫痫联盟（ILAE）HS 1 型与 2 型区分开来。虽然 T2wi 信号强度的增加不能归因于特定的组织病理学基质，即神经元减少或神经胶质细胞密度增加，但在 HS 标本中，海马内投射和纤维束发生扭曲，表明细胞成分、纤维网络以及细胞外基质的复杂紊乱。
我们的数据进一步证明，高分辨率 MRI 是一种有用且有前途的诊断工具，可用于研究 TLE 中海马的前-后延伸的病理，也可用于其他神经和神经退行性疾病。
