Language lateralization in temporal lobe epilepsy using functional MRI and probabilistic tractography

Purpose: Language functional magnetic resonance imaging (fMRI) is used to noninvasively assess hemispheric language specialization as part of the presurgical work-up in temporal lobe epilepsy (TLE). White matter asymmetries on diffusion tensor imaging (DTI) may be related to language specialization as shown in controls and TLE. To refine our understanding of the effect of epilepsy on the structure–function relationships, we focused on the arcuate fasciculus (ArcF) and the inferior occipitofrontal fasciculus (IOF) and tested the relationship between DTI- and fMRI-based lateralization indices in TLE.
Methods: fMRI with three language tasks and DTI were obtained in 20 patients (12 right and 8 left TLE). The ArcF, a major language-related tract, and the IOF were segmented bilaterally using probabilistic tractography to obtain fractional anisotropy (FA) lateralization indices. These were correlated with fMRI-based lateralization indices computed in the inferior frontal gyrus (Pearson's correlation coefficient).
Results: fMRI indices were left-lateralized in 16 patients and bilateral or right-lateralized in four. In the ArcF, FA was higher on the left than on the right side, reaching significance in right but not in left TLE. We found a positive correlation between ArcF anisotropy and fMRI-based lateralization indices in right TLE (p < 0.009), but not in left TLE patients. No correlation was observed for the IOF.
Conclusions: Right TLE patients with more left-lateralized functional activations also showed a leftward-lateralized arcuate fasciculus. The decoupling between the functional and structural indices of the ArcF underlines the complexity of the language network in left TLE patients.     

Possible remote functional reorganization in left temporal lobe epilepsy

Objective –  To provide functional magnetic resonance imaging-based insight into the impact of left temporal lobe epilepsy (TLE) on language-related functional re-organization.
Materials and methods –  Ten right-handed patients with left TLE were compared with 10 matched healthy controls. Regional brain activation during the language task was measured in the inferior frontal gyrus (IFG) and in the superior temporal gyrus (STG), and the regional inter-hemispheric lateralization index (LI) was calculated.
Results –  Left language lateralization was documented in all the patients and controls. Reduced lateralization in the IFG was due to decreased activity in the left frontal region rather than to increased activity in the right frontal region. The LI values in the STG correlated with the LI values in the IFG in the controls but not in the patients.
Conclusions –  The left IFG was most probably involved in the epileptogenesis and concomitant language-related cortical plasticity in patients with left TLE.     

累及Broca区低级别胶质瘤的BOLD—fMRI及语言功能区的可塑性研究（附15例分析）

目的探讨Bold—fMRI在功能区低级别胶质瘤中的应用及语言功能区的可塑性。方法对15例低级别胶质瘤及14例正常人行fMRI检查并作体素分析。病人在功能影像、术中电刺激指导下进行手术,结合语盲测评、影像评估及Karnofsky功能状态评分（KPS）等进行随访。结果病人较正常人半球激活指数（HAI）低,提示语言功能区重塑。肿瘤全切除11例,近全切除4例。术后短期内有不同程度失语7例,术后3个月均得以恢复。术后KPS评分较术前提高。结论Broca区低级别胶质瘤病人术前、术后语言功能区具有可塑性;应用术前功能影像及术中电刺激指导手术治疗,可提高肿瘤的切除程度,同时亦可保护语言功能。     

Correlation between white matter damage and gray matter lesions in multiple sclerosis patients

We observed the characteristics of white matter fibers and gray matter in multiple sclerosis patients, to identify changes in diffusion tensor imaging fractional anisotropy values following white matter fiber injury. We analyzed the correlation between fractional anisotropy values and changes in whole-brain gray matter volume. The participants included 20 patients with relapsing-remitting multiple sclerosis and 20 healthy volunteers as controls. All subjects underwent head magnetic resonance imaging and diffusion tensor imaging. Our results revealed that fractional anisotropy values decreased and gray matter volumes were reduced in the genu and splenium of corpus callosum, left anterior thalamic radiation, hippocampus, uncinate fasciculus, right corticospinal tract, bilateral cingulate gyri, and inferior longitudinal fasciculus in multiple sclerosis patients. Gray matter volumes were significantly different between the two groups in the right frontal lobe(superior frontal, middle frontal, precentral, and orbital gyri), right parietal lobe(postcentral and inferior parietal gyri), right temporal lobe(caudate nucleus), right occipital lobe(middle occipital gyrus), right insula, right parahippocampal gyrus, and left cingulate gyrus. The voxel sizes of atrophic gray matter positively correlated with fractional anisotropy values in white matter association fibers in the patient group. These findings suggest that white matter fiber bundles are extensively injured in multiple sclerosis patients. The main areas of gray matter atrophy in multiple sclerosis are the frontal lobe, parietal lobe, caudate nucleus, parahippocampal gyrus, and cingulate gyrus. Gray matter atrophy is strongly associated with white matter injury in multiple sclerosis patients, particularly with injury to association fibers.     

Reduced structural connectivity of a major frontolimbic pathway in generalized anxiety disorder

CONTEXT Emotion regulation deficits figure prominently in generalized anxiety disorder (GAD) and in other anxiety and mood disorders. Research examining emotion regulation and top-down modulation has implicated reduced coupling of the amygdala with prefrontal cortex and anterior cingulate cortex, suggesting altered frontolimbic white matter connectivity in GAD. OBJECTIVES To investigate structural connectivity between ventral prefrontal cortex or anterior cingulate cortex areas and the amygdala in GAD and to assess associations with functional connectivity between those areas. DESIGN Participants underwent diffusion-tensor imaging and functional magnetic resonance imaging. SETTING University magnetic resonance imaging facility. PARTICIPANTS Forty-nine patients with GAD and 39 healthy volunteer control subjects, including a matched subset of 21 patients having GAD without comorbid Axis I diagnoses and 21 healthy volunteers matched for age, sex, and education. MAIN OUTCOME MEASURES The mean fractional anisotropy values in the left and right uncinate fasciculus, as measured by tract-based analysis for diffusion-tensor imaging data. RESULTS Lower mean fractional anisotropy values in the bilateral uncinate fasciculus indicated reduced frontolimbic structural connectivity in patients with GAD. This reduction in uncinate fasciculus integrity was most pronounced for patients without comorbidity and was not observed in other white matter tracts. Across all participants, higher fractional anisotropy values were associated with more negative functional coupling between the pregenual anterior cingulate cortex and the amygdala during the anticipation of aversion. CONCLUSIONS Reduced structural connectivity of a major frontolimbic pathway suggests a neural basis for emotion regulation deficits in GAD. The functional significance of these structural differences is underscored by decreased functional connectivity between the anterior cingulate cortex and the amygdala in individuals with reduced structural integrity of the uncinate fasciculus.     

A qualitative and quantitative review of diffusion tensor imaging studies in reading and dyslexia

In this review paper we address whether deficits in reading (i.e. developmental dyslexia) are rooted in neurobiological anomalies in white matter tracts. Diffusion tensor imaging (DTI) offers an index of the connections between brain regions (via tractography) and of the white matter properties of these connections (via fractional anisotropy, FA). The reported studies generally show that lower FA values in left temporoparietal and frontal areas are indicative of poorer reading ability or dyslexia. Second, most studies have indicated that these regions coincide with the left arcuate fasciculus and corona radiata, with fewer studies suggesting a role for the posterior part of the corpus callosum or for more ventral tracts such as the inferior longitudinal fasciculus or the inferior fronto-occipital fasciculus. Finally, a quantitative activation likelihood estimation (ALE) meta-analysis on all reported studies that used a voxel-based approach reveals a cluster located close to the left temporoparietal region (x=-29, y=-17, z=26). Fibertracking through this cluster demonstrates that this region hosts both the left arcuate fasciculus and the left corona radiata.     

Arcuate fasciculus asymmetry has a hand in language function but not handedness

The importance of relationships between handedness, language lateralization and localization, and white matter tracts for language performance is unclear. The goal of the study was to investigate these relationships by examining arcuate fasciculus (AF) structural asymmetry (DTI) and functional asymmetry (fMRI) in language circuits, handedness, and linguistic performance. A large sample of right‐handed (n = 158) and atypical‐handed (n = 82) healthy adults underwent DTI at 3 T to assess number of streamlines and fractional anisotropy (FA) of the AF, and language fMRI. Language functions were assessed using standard tests of vocabulary, naming, verbal fluency, and complex ideation. Laterality indices (LIs) illustrated degree of asymmetry and lateralization patterns for the AF (streamlines and FA) and verb generation fMRI. Both handedness groups showed leftward lateralization bias for streamline and fMRI LIs and symmetry for FA LI. The proportion of subjects with left, right, or symmetric lateralization were similar between groups if based on AF LIs, but differed if based on fMRI LIs (p = 0.0016). Degree of right‐handedness was not associated with AF lateralization, but was associated with fMRI language lateralization (p = 0.0014). FA LI was not associated with performance on language assessments, but streamline LI was associated with better vocabulary and complex ideation performance in atypical‐handed subjects (p = 0.022 and p = 0.0098, respectively), and better semantic fluency in right‐handed subjects (p = 0.047); however, these did not survive multiple comparisons correction. We provide evidence that AF asymmetry is independent of hand preference, and while degree of right‐handedness is associated with hemispheric language lateralization, the majority of atypical‐handed individuals are left‐lateralized for language. Hum Brain Mapp 37:3297–3309, 2016. © 2016 Wiley Periodicals, Inc .     

Decreased integrity of the fronto-temporal fibers of the left inferior occipito-frontal fasciculus associated with auditory verbal hallucinations in schizophrenia

Auditory verbal hallucinations (AVH) have been proposed to result from altered connectivity between frontal speech production regions and temporal speech perception regions. Whilst the dorsal language pathway, serviced by the arcuate fasciculus, has been extensively studied in relation to AVH, the ventral language pathway, serviced by the inferior occipito-frontal fasciculus (IOFF) has been rarely studied in relation to AVH. This study examined whether structural changes in anatomically defined subregions of the IOFF were associated with AVH in patients with schizophrenia. Diffusion tensor imaging scans and clinical data were obtained from the Australian Schizophrenia Research Bank for 113 schizophrenia patients, of whom 39 had lifetime experience of AVH (18 had current AVH, 21 had remitted AVH), 74 had no lifetime experience of AVH, and 40 healthy controls. Schizophrenia patients with a lifetime experience of AVH exhibited reduced fractional anisotropy (FA) in the fronto-temporal fibers of the left IOFF compared to both healthy controls and schizophrenia patients without AVH. In contrast, structural abnormalities in the temporal and occipital regions of the IOFF were observed bilaterally in both patient groups, relative to the healthy controls. These results suggest that while changes in the structural integrity of the bilateral IOFF are associated with schizophrenia per se, integrity reductions in the fronto-temporal fibers of the left IOFF may be specifically associated with AVH.     

Lateralization of the arcuate fasciculus from childhood to adulthood and its relation to cognitive abilities in children

The arcuate fasciculus is a major white matter tract involved in language processing that has also been repeatedly implicated in intelligence and reasoning tasks. Language in the human brain is lateralized in terms of both function and structure, and while the arcuate fasciculus reflects this asymmetry, its pattern of lateralization is poorly understood in children and adolescents. We used diffusion tensor imaging (DTI) and tractography to examine arcuate fasciculus lateralization in a large (n = 183) group of healthy right‐handed volunteers aged 5–30 years; a subset of 68 children aged 5–13 years also underwent cognitive assessments. Fractional anisotropy and number of streamlines of the arcuate fasciculus were both significantly higher in the left hemisphere than the right hemisphere in most subjects, although some subjects (10%) were right lateralized. Age and gender effects on lateralization were not significant. Children receiving cognitive assessments were divided into three groups: a “left‐only” group in whom only the left side of the arcuate fasciculus could be tracked, a left‐lateralized group, and a right‐lateralized group. Scores on the Peabody Picture Vocabulary Test (PPVT) and NEPSY Phonological Processing task differed significantly among groups, with left‐only subjects outperforming the right‐lateralized group on the PPVT, and the left‐lateralized children scoring significantly better than the right‐lateralized group on phonological processing. In summary, DTI tractography demonstrates leftward arcuate fasciculus lateralization in children, adolescents, and young adults, and reveals a relationship between structural white matter lateralization and specific cognitive abilities in children. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.     

Multiparametric mapping of white matter reorganizations in patients with frontal glioma-related epilepsy

Aims

Epilepsy is a common symptom in diffuse lower-grade glioma (DLGG). The specific role of white matter (WM) alteration in patients with glioma-related epilepsy (GRE) is largely unknown. This study aims to investigate the reorganization of WM tracts and changes in structural networks related to GRE.

Methods

Diffusion-weighted images were collected from 70 patients with left frontal DLGG (GRE = 33, non-GRE = 37) and 41 healthy controls (HC). Tractometry with TractSeg was applied to segment tracts and quantify fractional anisotropy (FA) along each tract. Structural network was constructed using constrained spherical deconvolution and probabilistic tractography. FA and network properties were compared among three groups.

Results

Compared with HC, both GRE and non-GRE showed decreased FA in contralateral inferior fronto-occipital fasciculus, superior longitudinal fasciculus II and arcuate fasciculus, increased nodal efficiency in contralateral nodes of frontal–parietal and limbic networks, whereas decreased degree centrality and betweenness centrality in nodes of dorsal temporal lobe and rostral middle frontal gyrus (rMFG). Additionally, when compared GRE with non-GRE, increased FA in contralateral corticospinal tract (CST) and lower betweenness centrality in paracentral lobule (PCL) in GRE (all p < 0.05 after Bonferroni correction).

Conclusion

This study indicates that patients with left frontal DLGG exhibit complex WM reorganization, and the altered regions mainly concentrated in the language, frontal–parietal and limbic networks. Moreover, the preserved integrity in contralateral CST and server decreased nodal betweenness in PCL may be potential neuroimaging markers underlying the occurrence of presurgical seizures of GRE.     

Is the left uncinate fasciculus essential for language?

Despite a better understanding of the anatomy of the uncinate fasciculus (UF), its function remains poorly known. Our aim was to study the exact role of UF in language, and the possible existence of parallel distributed language networks within the “ventral stream”, underlaid by distinct subcortical tracts – namely the inferior occipito-temporal fasciculus (IOF) and UF. We report a series of 13 patients operated on awake for a glioma involving the left anterior temporal lobe or the orbitofrontal area. We used intraoperative electrostimulation, to perform accurate and reliable anatomofunctional correlations both at cortical and subcortical levels. Using postoperative MRI, we correlated these functional findings with the anatomical locations of the sites where language disturbances were elicited by stimulation. Intraoperative cortical stimulation found perilesional language sites in all cases. Subcortically, semantic paraphasia were induced in the 13 patients by stimulating the IOF, and phonological paraphasia were generated in 6 patients by stimulating the arcuate fasciculus. Interestingly, subcortical stimulation never elicited any language disturbances when performed at the level of the UF. Moreover, after a transient postoperative language deficit, all patients recovered, despite the removal of at least one part of the UF, as confirmed by control MRI. We suggest that UF is not systematically essential for language. It can be explained by the fact that the “semantic ventral stream” might be constituted by at least two parallel pathways, i. e. a direct pathway underlaid by the IOF, crucial for language semantics, and an indirect pathway subserved by UF, which can be functionally compensated. However, we have to underline the fact not all language functions can be probed during surgery, and that more sensitive tasks have now to be added.     

Alterations in white matter pathways in Angelman syndrome

Aim Angelman syndrome is a neurogenetic disorder characterized by severe intellectual disability, absent speech, seizures, and outbursts of laughter. The aim of this study was to utilize diffusion tensor imaging (DTI) to examine alterations in white matter pathways in Angelman syndrome, with an emphasis on correlations with clinical severity. Method DTI was used to examine the arcuate fasciculus (AF), uncinate fasciculus (UF), inferior longitudinal fasciculus (ILF), inferior fronto‐occipital fasciculus (IFOF), and the corpus callosum (CC). We enrolled 14 children aged 8 to 17 years (mean age 10y 8mo; SD 2y 7mo) with Angelman syndrome (seven male; seven female) and 13 typically developing children, aged 8 to 17 years, for comparison (five male; eight female; mean age 12y; SD 2y 9mo). Individuals with Angelman syndrome were assessed using standardized measures of development, language, and behaviour. Results The children with Angelman syndrome exhibited lower fractional anisotropy and increased radial diffusivity values than the comparison group for the AF, UF, ILF, and CC (p<0.006 corrected for multiple comparisons). They also had lower fractional anisotropy values for the IFOF and higher radial diffusivity values for the left IFOF (p<0.006). Additionally, children with Angelman syndrome had significantly higher apparent diffusion coefficient values in the AF, CC, ILF, and the left IFOF (p<0.006). Significant correlations were noted between DTI parameters and some of the clinical assessment outcomes (e.g. language, socialization, cognition) for three of the temporal pathways (AF, UF, ILF; p<0.05). Interpretation Changes in DTI parameters in individuals with Angelman syndrome suggest decreased/delayed myelination, decreased axonal density or diameter, or aberrant axonal organization. Our findings suggest a generalized white matter alteration throughout the brain in those with Angelman syndrome; however, only the alterations in temporal white matter pathways were associated with language and cognitive and social functioning.     

Reorganization of the right arcuate fasciculus following left arcuate fasciculus resection in children with intractable epilepsy

The authors evaluated postsurgical reorganization of the arcuate fasciculus longitudinally using diffusion tensor imaging in 10 children with intractable epilepsy, whose resections included the left arcuate fasciculus. Evaluation of fractional anisotropy before and after surgery (mean follow-up: 7.5 months) showed a significant increase (P = .002) in the right arcuate fasciculus during follow-up. There was marked enlargement of the right arcuate fasciculus postsurgically in 8 patients. The change in right arcuate fasciculus fractional anisotropy values showed a positive correlation with interval between resection and postsurgical magnetic resonance imaging (MRI) (P = .044). Comparison of 10 age-matched controls to patients pre- and postsurgery showed significantly reduced presurgery fractional anisotropy in the left (P = .018) and right (P = .036) arcuate fasciculus and no difference in postsurgery fractional anisotropy in the right arcuate fasciculus (P = .399) in patients. These findings suggest a compensatory reorganization in the right arcuate fasciculus in children with intractable epilepsy following left arcuate fasciculus resection.     

Aphasia induced by gliomas growing in the ventrolateral frontal region: assessment with diffusion MR tractography, functional MR imaging and neuropsychology

IntroductionLesions in the ventrolateral region of the dominant frontal lobe have been historically associated with aphasia. Recent imaging results suggest that frontal language regions extend beyond classically defined Broca’s area to include the ventral precentral gyrus (VPCG) and the arcuate fasciculus (AF). Frontal gliomas offer a unique opportunity to identify structures that are essential for speech production. The aim of this prospective study was to investigate the correlation between language deficits and lesion location in patients with gliomas.MethodsNineteen patients with glioma and 10 healthy subjects were evaluated with diffusion tensor imaging magnetic resonance (MR) tractography, functional MR (verb generation task) and the Aachener Aphasie Test. Patients were divided into two groups according to lesion location with respect to the ventral precentral sulcus: (i) anterior (n = 8) with glioma growing in the inferior frontal gyrus (IFG) and underlying white matter; (ii) posterior (n = 11) with glioma growing in the VPCG and underlying white matter. Virtual dissection of the AF, frontal intralobar tract, uncinate fasciculus (UF) and inferior frontal occipital fasciculus (IFOF) was performed with a deterministic approach.ResultsSeven posterior patients showed aphasia classified as conduction (4), Broca (1), transcortical motor (1) and an isolated deficit of semantic fluency; one anterior patient had transcortical mixed aphasia. All posterior patients had invasion of the VPCG, however only patients with aphasia had also lesion extension to the AF as demonstrated by tractography dissections. All patients with language deficits had high grade glioma. Groups did not differ regarding tumour volume. A functional pars opercularis was identified with functional MR imaging (fMRI) in 17 patients.ConclusionsGliomas growing in the left VPCG are much more likely to cause speech deficits than gliomas infiltrating the IFG, including Broca’s area. Lesion extension to the AF connecting frontal to parietal and temporal regions is an important mechanism for the appearance of aphasia.     

MEG imaging of recurrent gliomas reveals functional plasticity of hemispheric language specialization

In patients with gliomas, changes in hemispheric specialization for language determined by magnetoencephalography (MEG) were analyzed to elucidate the impact of treatment and tumor recurrence on language networks. Demonstration of reorganization of language networks in these patients has significant implications on the prevention of postoperative functional loss and recovery. Whole‐brain activity during an auditory verb generation task was estimated from MEG recordings in a group of 73 patients with recurrent gliomas. Hemisphere of language dominance was estimated using the language laterality index (LI), a measure derived from the task. The initial scan was performed prior to resection; patients subsequently underwent surgery and adjuvant treatment. A second scan was performed upon recurrence prior to repeat resection. The relationship between the shift in LI between scans and demographics, anatomic location, pathology, and adjuvant treatment was analyzed. Laterality shifts were observed between scans; the median percent change was 29.1% across all patients. Laterality shift magnitude and relative direction were associated with the initial position of language dominance; patients with increased lateralization experienced greater shifts than those presenting more bilateral representation. A change in LI from left or right to bilateral (or vice versa) occurred in 23.3% of patients; complete switch occurred in 5.5% of patients. Patients with tumors within the language‐dominant hemisphere experienced significantly greater shifts than those with contralateral tumors. The majority of patients with glioma experience shifts in language network organization over time which correlate with the relative position of language lateralization and tumor location.     

Disrupted white matter integrity of corticopontine-cerebellar circuitry in schizophrenia

Evidence for white matter abnormalities in patients with schizophrenia is increasing. Decreased fractional anisotropy (FA) in interhemispheric commissural fibers as well as long-ranging fronto-parietal association fibers belongs to the most frequent findings. The present study used tract-based spatial statistics to investigate white matter integrity in 35 patients with schizophrenia and 35 healthy volunteers. We found that patients exhibited significantly decreased FA relative to healthy subjects in the corpus callosum, the cerebral peduncle, the left inferior fronto-occipital fasciculus, the anterior thalamic radiation, the right posterior corona radiata, the middle cerebellar peduncle, and the right superior longitudinal fasciculus. Increased FA was detectable in the inferior sections of the corticopontine-cerebellar circuit. Present data indicate extended cortical-subcortical alterations of white matter integrity in schizophrenia using advanced data analysis strategies. They corroborate preceding findings of white matter structural deficits in mainly long-ranging association fibers and provide first evidence for neuroplastic changes in terms of an increased directionality in more inferior fiber tracts.     

Regional and hemispheric determinants of language laterality: Implications for preoperative fMRI

Language is typically a function of the left hemisphere but the right hemisphere is also essential in some healthy individuals and patients. This inter‐subject variability necessitates the localization of language function, at the individual level, prior to neurosurgical intervention. Such assessments are typically made by comparing left and right hemisphere language function to determine “language lateralization” using clinical tests or fMRI. Here, we show that language function needs to be assessed at the region and hemisphere specific level, because laterality measures can be misleading. Using fMRI data from 82 healthy participants, we investigated the degree to which activation for a semantic word matching task was lateralized in 50 different brain regions and across the entire cortex. This revealed two novel findings. First, the degree to which language is lateralized across brain regions and between subjects was primarily driven by differences in right hemisphere activation rather than differences in left hemisphere activation. Second, we found that healthy subjects who have relatively high left lateralization in the angular gyrus also have relatively low left lateralization in the ventral precentral gyrus. These findings illustrate spatial heterogeneity in language lateralization that is lost when global laterality measures are considered. It is likely that the complex spatial variability we observed in healthy controls is more exaggerated in patients with brain damage. We therefore highlight the importance of investigating within hemisphere regional variations in fMRI activation, prior to neuro‐surgical intervention, to determine how each hemisphere and each region contributes to language processing. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.     

Oscillatory and structural signatures of language plasticity in brain tumor patients: A longitudinal study

Recent evidence suggests that damage to the language network triggers its functional reorganization. Yet, the spectro‐temporal fingerprints of this plastic rearrangement and its relation to anatomical changes is less well understood. Here, we combined magnetoencephalographic recordings with a proxy measure of white matter to investigate oscillatory activity supporting language plasticity and its relation to structural reshaping. First, cortical dynamics were acquired in a group of healthy controls during object and action naming. Results showed segregated beta (13–28 Hz) power decreases in left ventral and dorsal pathways, in a time‐window associated to lexico‐semantic processing (~250–500 ms). Six patients with left tumors invading either ventral or dorsal regions performed the same naming task before and 3 months after surgery for tumor resection. When longitudinally comparing patients'' responses we found beta compensation mimicking the category‐based segregation showed by controls, with ventral and dorsal damage leading to selective compensation for object and action naming, respectively. At the structural level, all patients showed preoperative changes in white matter tracts possibly linked to plasticity triggered by tumor growth. Furthermore, in some patients, structural changes were also evident after surgery and showed associations with longitudinal changes in beta power lateralization toward the contralesional hemisphere. Overall, our findings support the existence of anatomo‐functional dependencies in language reorganization and highlight the potential role of oscillatory markers in tracking longitudinal plasticity in brain tumor patients. By doing so, they provide valuable information for mapping preoperative and postoperative neural reshaping and plan surgical strategies to preserve language function and patient''s quality of life.     

皮质下缺血性血管病患者联络纤维的扩散张量成像分析和认知功能相关研究

【摘要】 目的 运用磁共振成像（magnetic resonance imaging,MRI）基于白质地图的扩散张量成像（diffusion tensor imaging,DTI）技术研究皮质下缺血性血管病（subcortical ischemic vascular disease,SIVD）患者联络纤维的超微结构改变,并分析DTI参数与认知功能的关系。 方法 连续入选40例SIVD患者,分为血管性认知障碍组18例,无认知障碍组22例,另设立20例正常老年人为对照组。对三组进行MRI检查并对其白质改变进行评分,对联络纤维进行基于白质地图分析（atlase based analysis,ABA）DTI成像,比较组间部分各向异性指数（fractional anisotrophy,FA）、平均扩散率（mean diffusivity,MD）差异,并对SIVD患者DTI参数与蒙特利尔认知评估量表（Montreal Cognitive Assessment,MoCA）得分进行相关性分析。 结果 无认知障碍组较正常组在右侧矢状层（下纵束/下额枕束）、右侧扣带（海马部）及左侧上额枕束的FA值减低;认知障碍组较正常组存在广泛的联络纤维FA值降低,差异均具有显著性。无认知障碍组与正常组比较,仅左侧扣带海马部及左侧上纵束MD值无显著差异,余联络纤维的MD值均显著增高;认知障碍组较正常组存在广泛的联络纤维MD值增高,差异均具有显著性。与无认知功能障碍组比较,认知功能障碍组在双侧矢状层（下纵束/下额枕束）、双侧扣带扣带回部、海马部、双侧上纵束、双侧上额枕束及双侧钩束的FA值减低,MD值增高,差异具有显著性。SIVD患者双侧矢状层（下纵束/下额枕束）、扣带扣带回部、上纵束、上额枕束及钩束和左侧扣带海马部的FA值与MoCA评分呈正相关,MD值与MoCA评分呈负相关。 结论 SIVD患者联络纤维的FA值减低,MD值增高,且DTI参数与其认知功能密切相关。     

A sensitive diffusion tensor imaging quantification method to detect language laterality in children: correlation with the Wada test

Using diffusion tensor imaging tractography and color-coded anisotropy map quantification, we investigated asymmetry of the arcuate fasciculus to determine language laterality in children and compared it with the Wada test. Arcuate fasciculus volume and fractional anisotropy were measured after tractography. We also quantified the fiber orientation distribution in the arcuate fasciculus region, ie, the fraction of arcuate fasciculus fibers oriented in the anteroposterior and mediolateral directions. A Laterality Index was calculated for each of the measured parameters. Volumetric analysis of the arcuate fasciculus showed asymmetry favoring the language dominant hemisphere (P = .02), while fractional anisotropy showed no significant asymmetry (P = .07). The mean anteroposterior and mediolateral components on the language dominant side were significantly higher than on the nondominant side (P = .003 and .002, respectively). The Laterality Index values were concordant with the Wada test results except for 1 case. Fractional anisotropy also falsely lateralized language in 1 case.