脑白质病变临床特点与白质传导束关系研究进展

脑白质病变(WML)是脑小血管病的一种,与年龄、高血压等血管危险因素相关。WML与脑卒中、记忆、语言、步态及情绪等有密切联系,而且其进展预示着临床预后较差。利用MR微细结构成像技术了解到脑白质传导束的病变与其多样化的临床表现相关。MRI技术为WML的病理生理机制提供了依据,为进一步了解WML多样化临床表现提供了新视角。     

缺血性脑白质病变的研究进展

缺血性脑白质病变是最常见的白质脑病类型之一。文章就其危险因素、发病机制、遗传学、临床表现、影像学、治疗等方面的进展做一综述。     

White matter extension of the Melbourne Children's Regional Infant Brain atlas: M‐CRIB‐WM

Brain atlases providing standardised identification of neonatal brain regions are key in investigating neurological disorders of early childhood. Our previously developed Melbourne Children's Regional Infant Brain (M‐CRIB) and M‐CRIB 2.0 neonatal brain atlases provide standardised parcellation of 100 brain regions including cortical, subcortical, and cerebellar regions. The aim of this study was to extend M‐CRIB atlas coverage to include 54 white matter (WM) regions. Participants were 10 healthy term‐born neonates that were used to create the initial M‐CRIB atlas. WM regions were manually segmented based on T₂ images and co‐registered diffusion tensor imaging‐based, direction‐encoded colour maps. Our labelled regions imitate the Johns Hopkins University neonatal atlas, with minor anatomical modifications. All segmentations were reviewed and approved by a paediatric radiologist and a neurosurgery research fellow for anatomical accuracy. The resulting neonatal WM atlas comprises 54 WM regions: 24 paired regions, and six unpaired regions comprising five corpus callosum subdivisions, and one pontine crossing tract. Detailed protocols for manual WM parcellations are provided, and the M‐CRIB‐WM atlas is presented together with the existing M‐CRIB cortical, subcortical, and cerebellar parcellations in 10 individual neonatal MRI data sets. The novel M‐CRIB‐WM atlas, along with the M‐CRIB cortical and subcortical atlases, provide neonatal whole brain MRI coverage in the first multi‐subject manually parcellated neonatal atlas compatible with atlases commonly used at older time points. The M‐CRIB‐WM atlas is publicly available, providing a valuable tool that will help facilitate neuroimaging research into neonatal brain development in both healthy and diseased states.     

28例脑淀粉样血管病白质损害的临床特征

目的明确脑淀粉样血管病(CAA)患者白质损害的影像学特征,以及与其他脑小血管病(CSVD)标志物的相关性。方法回顾性分析2014年12月至2016年12月收集的28例很可能的CAA患者(CAA组)和56例合并CSVD危险因素的健康老年人(非CAA组)在临床信息,影像学标志物和白质损害之间的差异;白质损害分别从脑网络连接改变和定量白质高信号(WMH)体积的严重程度和分布特征(后-前部梯度)进行评估,以弥散张量成像中各向异性分数(FA)作为测量脑网络连接参数。分析CAA患者白质损害与脑微出血灶(CMBs)、血管周间隙(PVS)、CSVD积分等影像标志物的相关性。结果白质损害方面,与非CAA组比较,CAA组的全脑WMH体积(P0.001)和后-前部梯度(P=0.004)增加,FA后部均值(P=0.037)和后-前部梯度(P=0.004)降低。相关性分析表明:CAA组的全脑FA均值与WMH体积无相关性(P=0.151),而两组的后-前部梯度线性相关(P=0.029);全脑FA均值与脑叶CMBs数目(P=0.036)、CSVD积分(P=0.049)存在相关性,但这一相关性未在WMH体积中发现。结论脑网络连接下降、WMH体积增加是CAA白质损害的重要影像学标志物,具有后部分布为主的显著特征。脑网络连接下降可在一定程度上反映CAA的病理改变和疾病严重程度。     

Temporal Dynamics of Brain White Matter Plasticity in Sighted Subjects during Tactile Braille Learning: A Longitudinal Diffusion Tensor Imaging Study

The white matter (WM) architecture of the human brain changes in response to training, though fine-grained temporal characteristics of training-induced white matter plasticity remain unexplored. We investigated white matter microstructural changes using diffusion tensor imaging at five different time points in 26 sighted female adults during 8 months of training on tactile braille reading. Our results show that training-induced white matter plasticity occurs both within and beyond the trained sensory modality, as reflected by fractional anisotropy (FA) increases in somatosensory and visual cortex, respectively. The observed changes followed distinct time courses, with gradual linear FA increase along the training in the somatosensory cortex and sudden visual cortex cross-modal plasticity occurring after braille input became linguistically meaningful. WM changes observed in these areas returned to baseline after the cessation of learning in line with the supply–demand model of plasticity. These results also indicate that the temporal dynamics of microstructural plasticity in different cortical regions might be modulated by the nature of computational demands. We provide additional evidence that observed FA training-induced changes are behaviorally relevant to tactile reading. Together, these results demonstrate that WM plasticity is a highly dynamic process modulated by the introduction of novel experiences.SIGNIFICANCE STATEMENT Throughout the lifetime the human brain is shaped by various experiences. Training-induced reorganization in white matter (WM) microstructure has been reported, but we know little about its temporal dynamics. To fill this gap, we scanned sighted subjects five times during tactile braille reading training. We observed different dynamics of WM plasticity in the somatosensory and visual cortices implicated in braille reading. The former showed a continuous increase in WM tissue anisotropy along with tactile training, while microstructural changes in the latter were observed only after the participants learned to read braille words. Our results confirm the supply–demand model of brain plasticity and provide evidence that WM reorganization depends on distinct computational demands and functional roles of regions involved in the trained skill.     

White matter microstructure alterations in bipolar disorder

Genetic, neuropathological and magnetic resonance imaging findings support the presence of diffuse white matter cytoarchitectural disruption in bipolar disorder. In this study, diffusion-weighted imaging (DWI) was applied to study cortical white matter microstructure organisation in 24 patients with DSM-IV bipolar disorder and 35 matched normal controls. DWI images were obtained using a 1.5 Tesla scanner and apparent diffusion coefficient (ADC) values were determined over regions of interest placed, bilaterally, in the frontal, temporal, parietal, and occipital white matter. Significantly increased ADC values were found in bipolar patients with respect to normal controls in the right temporal lobe, left parietal lobe and bilateral occipital lobes. ADC values did not associate significantly with age or with clinical variables (p>0.05). Diffuse cortical white matter alterations on DWI in bipolar disorder denote widespread disruption of white matter integrity and may be due to altered myelination and/or axonal integrity.     

White Matter Lesions in Children and Adolescents With Migraine

BackgroundThe etiology and clinical importance of white matter lesions in migraine remain poorly understood. To understand these issues more fully, we reviewed the brain magnetic resonance imaging scans of pediatric patients and assessed the relationships between white matter lesions, migraine type, patent foramen ovale, and right-to-left shunting.MethodsThe magnetic resonance imaging scans of a cohort of children (n = 89) and adolescents, ages 6 to 18 years, who participated in a study of migraine and patent foramen ovale were reviewed. All children in the cohort had undergone saline contrast transthoracic echocardiography and transcranial Doppler studies.ResultsWhite matter lesions were detected in 15 of the 89 patients (17%). White matter lesions were small (<5 mm) in the majority (10/15; 66%). We observed no relationship between the presence of white matter lesions and (1) migraine type (six patients with white matter lesions among 35 with migraine with aura [17%] vs. nine with white matter lesions among 54 without aura [17%]; P = 1.0); (2) patent foramen ovale (five with white matter lesions among 35 with patent foramen ovale [14%] vs. 10 with white matter lesions among 54 without patent foramen ovale [19%]; P = 0.77); or (3) shunt size (two large shunts in 15 with white matter lesions [13%] vs. nine large shunts among 72 without white matter lesions [13%]; P = 1.0).ConclusionsThese results indicate that small white matter lesions are not infrequent in children and adolescents with migraine. However, no relationships between white matter lesions and migraine type, patent foramen ovale, or degree of right-to-left shunting were observed.     

The Cholesterol Side-Chain Cleavage Complex in Human Brain White Matter

Specific antibodies obtained in rabbits after injection of bovine cholesterol side-chain cleavage enzymes cytochrome P-450scc, adrenodoxin and adrenodoxin-reductase were used for immunohistochemical studies in human brain. The three enzymes were co-localized in the white matter of the cerebellum. This observation strongly suggests the existence of steroidogenic activity in human oligodendrocytes, as previously reported in the rat, and suggests that the concept of 'neurosteroids' can be applied to Δ5–3ß-hydroxysteroid metabolites of cholesterol that accumulate in human brain.     

脑大动脉病变与脑白质高信号的相关性研究进展

脑大、小血管共同构成了脑的血管树,它们在结构和功能上有一定的相关性。近年来,脑 大血管病变与脑小血管病之间相关关系的研究逐渐受到重视。大动脉粥样硬化、动脉延长扩张及管 壁僵硬度增大从不同侧面反映了大血管病变的特点,脑白质高信号是脑小血管病重要的影像学表现。 本文对动脉粥样硬化、动脉延长扩张及僵硬度增大与脑白质高信号之间的相关性进行综述,以探讨 脑大血管病变与脑小血管病的关系。