Department of Psychiatry, University of California, San Diego, California.
Center for Multimodal Imaging and Genetics, University of California, San Diego, California.
Epilepsia. 2019 May;60(5):935-947. doi: 10.1111/epi.14736. Epub 2019 Apr 25.
Temporal lobe epilepsy (TLE) is known to affect large-scale gray and white matter networks, and these network changes likely contribute to the verbal memory impairments observed in many patients. In this study, we investigate multimodal imaging patterns of brain alterations in TLE and evaluate the sensitivity of different imaging measures to verbal memory impairment.
Diffusion tensor imaging (DTI), volumetric magnetic resonance imaging (vMRI), and resting-state functional MRI (rs-fMRI) were evaluated in 46 patients with TLE and 33 healthy controls to measure patterns of microstructural, structural, and functional alterations, respectively. These measurements were obtained within the white matter directly beneath neocortex (ie, superficial white matter [SWM]) for DTI and across neocortex for vMRI and rs-fMRI. The degree to which imaging alterations within left medial temporal lobe/posterior cingulate (LMT/PC) and left lateral temporal regions were associated with verbal memory performance was evaluated.
Patients with left TLE and right TLE both demonstrated pronounced microstructural alterations (ie, decreased fractional anisotropy [FA] and increased mean diffusivity [MD]) spanning the entire frontal and temporolimbic SWM, which were highly lateralized to the ipsilateral hemisphere. Conversely, reductions in cortical thickness in vMRI and alterations in the magnitude of the rs-fMRI response were less pronounced and less lateralized than the microstructural changes. Both stepwise regression and mediation analyses further revealed that FA and MD within SWM in LMT/PC regions were the most robust predictors of verbal memory, and that these associations were independent of left hippocampal volume.
These findings suggest that microstructural loss within the SWM is pronounced in patients with TLE, and injury to the SWM within the LMT/PC region plays a critical role in verbal memory impairment.
已知颞叶癫痫（TLE）会影响大脑的灰质和白质大网络，这些网络变化可能导致许多患者出现言语记忆障碍。本研究旨在探讨 TLE 患者大脑改变的多模态影像学模式，并评估不同影像学测量方法对言语记忆障碍的敏感性。
对 46 例 TLE 患者和 33 名健康对照者进行弥散张量成像（DTI）、容积磁共振成像（vMRI）和静息态功能磁共振成像（rs-fMRI）检查，分别测量微观结构、结构和功能改变的模式。这些测量是在皮质下的白质（即浅表白质[SWM]）内进行 DTI 测量，在皮质内进行 vMRI 和 rs-fMRI 测量。评估左侧内侧颞叶/后扣带回（LMT/PC）和左侧颞叶外侧区域内的影像学改变与言语记忆表现的相关性。
左侧 TLE 和右侧 TLE 患者均表现出广泛的微观结构改变（即各向异性分数[FA]降低和平均扩散度[MD]升高），横跨整个额颞叶 SWM，高度向同侧半球偏侧化。相比之下，vMRI 中皮质厚度的减少和 rs-fMRI 响应幅度的改变比微观结构变化程度小，且偏侧化程度低。逐步回归和中介分析进一步表明，LMT/PC 区域 SWM 内的 FA 和 MD 是言语记忆的最有力预测因子，并且这些关联独立于左侧海马体积。
这些发现表明，TLE 患者的 SWM 内微观结构丢失明显，LMT/PC 区域的 SWM 损伤在言语记忆障碍中起着关键作用。
