Abnormalities of magnetic resonance spectroscopy and diffusion tensor imaging are correlated with executive dysfunction in patients with ischemic leukoaraiosis

Dynamic network properties of the superior temporal gyrus mediate the impact of brain age gap on chronic aphasia severity

Brain structure deteriorates with aging and predisposes an individual to more severe language impairments (aphasia) after a stroke. However, the underlying mechanisms of this relation are not well understood. Here we use an approach to model brain network properties outside the stroke lesion, network controllability, to investigate relations among individualized structural brain connections, brain age, and aphasia severity in 93 participants with chronic post-stroke aphasia. Controlling for the stroke lesion size, we observe that lower average controllability of the posterior superior temporal gyrus (STG) mediates the relation between advanced brain aging and aphasia severity. Lower controllability of the left posterior STG signifies that activity in the left posterior STG is less likely to yield a response in other brain regions due to the topological properties of the structural brain networks. These results indicate that advanced brain aging among individuals with post-stroke aphasia is associated with disruption of dynamic properties of a critical language-related area, the STG, which contributes to worse aphasic symptoms. Because brain aging is variable among individuals with aphasia, our results provide further insight into the mechanisms underlying the variance in clinical trajectories in post-stroke aphasia.

Disconnection of Network Hubs Underlying the Executive Function Deficit in Patients with Ischemic Leukoaraiosis

BACKGROUND

Cognitive impairment is the most common clinical manifestation of ischemic leukoaraiosis (ILA), but the underlying neurobiological pathways have not been well elucidated. Recently, it was thought that ILA is a "disconnection syndrome". Disorganized brain connectome were considered the key neuropathology underlying cognitive deficits in ILA patients.

OBJECTIVE

We aimed to detect the disruption of network hubs in ILA patients using a new analytical method called voxel-based eigenvector centrality (EC) mapping.

METHODS

Subjects with moderate to severe white matters hyperintensities (Fazekas score ≥3) and healthy controls (HCs) (Fazekas score = 0) were included in the study. The resting-state functional magnetic resonance imaging and the EC mapping approach were performed to explore the alteration of whole-brain network connectivity in ILA patients.

RESULTS

Relative to the HCs, the ILA patients exhibited poorer cognitive performance in episodic memory, information processing speed, and executive function (all ps < 0.0125). Additionally, compared with HCs, the ILA patients had lower functional connectivity (i.e., EC values) in the medial parts of default-mode network (i.e., bilateral posterior cingulate gyrus and ventral medial prefrontal cortex [vMPFC]). Intriguingly, the functional connectivity strength at the right vMPFC was positively correlated with executive function deficit in the ILA patients.

CONCLUSION

The findings suggested disorganization of the hierarchy of the default-mode regions within the whole-brain network in patients with ILA and advanced our understanding of the neurobiological mechanism underlying executive function deficit in ILA.

Sex Differences in Cerebral Small Vessel Disease: A Systematic Review and Meta-Analysis

Background: Cerebral small vessel disease (SVD) is a common cause of stroke, mild cognitive impairment, dementia and physical impairments. Differences in SVD incidence or severity between males and females are unknown. We assessed sex differences in SVD by assessing the male-to-female ratio (M:F) of recruited participants and incidence of SVD, risk factor presence, distribution, and severity of SVD features. Methods: We assessed four recent systematic reviews on SVD and performed a supplementary search of MEDLINE to identify studies reporting M:F ratio in covert, stroke, or cognitive SVD presentations (registered protocol: CRD42020193995). We meta-analyzed differences in sex ratios across time, countries, SVD severity and presentations, age and risk factors for SVD. Results: Amongst 123 relevant studies (n = 36,910 participants) including 53 community-based, 67 hospital-based and three mixed studies published between 1989 and 2020, more males were recruited in hospital-based than in community-based studies [M:F = 1.16 (0.70) vs. M:F = 0.79 (0.35), respectively; p < 0.001]. More males had moderate to severe SVD [M:F = 1.08 (0.81) vs. M:F = 0.82 (0.47) in healthy to mild SVD; p < 0.001], and stroke presentations where M:F was 1.67 (0.53). M:F did not differ for recent (2015-2020) vs. pre-2015 publications, by geographical region, or age. There were insufficient sex-stratified data to explore M:F and risk factors for SVD. Conclusions: Our results highlight differences in male-to-female ratios in SVD severity and amongst those presenting with stroke that have important clinical and translational implications. Future SVD research should report participant demographics, risk factors and outcomes separately for males and females. Systematic Review Registration: [PROSPERO], identifier [CRD42020193995].

Neuroimaging Anomalies in Community-Dwelling Asymptomatic Adults With Very Early-Stage White Matter Hyperintensity

White matter hyperintensity (WMH) is common in healthy adults in their 60s and can be seen as early as in their 30s and 40s. Alterations in the brain structural and functional profiles in adults with WMH have been repeatedly studied but with a focus on late-stage WMH. To date, structural and functional MRI profiles during the very early stage of WMH remain largely unexplored. To address this, we investigated multimodal MRI (structural, diffusion, and resting-state functional MRI) profiles of community-dwelling asymptomatic adults with very early-stage WMH relative to age-, sex-, and education-matched non-WMH controls. The comparative results showed significant age-related and age-independent changes in structural MRI-based morphometric measures and resting-state fMRI-based measures in a set of specific gray matter (GM) regions but no global white matter changes. The observed structural and functional anomalies in specific GM regions in community-dwelling asymptomatic adults with very early-stage WMH provide novel data regarding very early-stage WMH and enhance understanding of the pathogenesis of WMH.

Disrupted Structural Brain Connectome Is Related to Cognitive Impairment in Patients With Ischemic Leukoaraiosis

Ischemic leukoaraiosis (ILA) is related to cognitive impairment and vascular dementia in the elderly. One possible mechanism could be the disruption of white matter (WM) tracts and network function that connect distributed brain regions involved in cognition. The purpose of this study was to investigate the relationship between structural connectome and cognitive functions in ILA patients. A total of 89 patients with ILA (Fazekas score ≥ 3) and 90 healthy controls (HCs) underwent comprehensive neuropsychological examinations and diffusion tensor imaging scans. The tract-based spatial statistics approach was employed to investigate the WM integrity. Graph theoretical analysis was further applied to construct the topological architecture of the structural connectome in ILA patients. Partial correlation analysis was used to investigate the relationships between network measures and cognitive performances in the ILA group. Compared with HCs, the ILA patients showed widespread WM integrity disruptions. The ILA group displayed increased characteristic path length (L _p) and decreased global network efficiency at the level of the whole brain relative to HCs, and reduced nodal efficiencies, predominantly in the frontal-subcortical and limbic system regions. Furthermore, these structural connectomic alterations were associated with cognitive impairment in ILA patients. The association between WM changes (i.e., fractional anisotropy and mean diffusivity measures) and cognitive function was mediated by the structural connectivity measures (i.e., local network efficiency and L _p). In conclusion, cognitive impairment in ILA patients is related to microstructural disruption of multiple WM fibers and topological disorganization of structural networks, which have implications in understanding the relationship between ILA and the possible attendant cognitive impairment.

Cognitive impairment in sporadic cerebral small vessel disease: A systematic review and meta-analysis

This paper is a proposal for an update on the characterization of cognitive impairments associated with sporadic cerebral small vessel disease (SVD). We pose a series of questions about the nature of SVD-related cognitive impairments and provide answers based on a comprehensive review and meta-analysis of published data from 69 studies. Although SVD is thought primarily to affect executive function and processing speed, we hypothesize that SVD affects all major domains of cognitive ability. We also identify low levels of education as a potentially modifiable risk factor for SVD-related cognitive impairment. Therefore, we propose the use of comprehensive cognitive assessments and the measurement of educational level both in clinics and research settings, and suggest several recommendations for future research.

Use of Multimodal Magnetic Resonance Imaging Techniques to Explore Cognitive Impairment in Leukoaraiosis

Leukoaraiosis, also referred to as white-matter hyperintensities (WMHs) or age-related white matter changes, is the most frequently seen lesion on brain magnetic resonance images (MRI) in the elderly. LA is a subject of intense research interest, and is correlated with stroke, cognitive impairment or dementia, disturbances, affective disorders, and poor prognoses. Rapid advances in neuroimaging have enabled greater understanding of LA associated with aging-related cognitive decline or dementia. Recently, the techniques of multimodal MRI, such as structural MRI (sMRI), resting-state functional MRI (rs-MRI), cerebrovascular reactivity (CVR), diffusion tensor imaging (DTI), magnetic resonance spectroscopy (MRS), and dynamic contrast-enhanced MRI (DCE-MRI), have been used to explore the underlying mechanism of cognitive impairment in patients with LA. These multimodal MRI techniques may provide further insights into the structural and functional changes of LA with cognitive dysfunction.

Associations between executive function impairment and biochemical abnormalities in bipolar disorder with suicidal ideation

BACKGROUND

Executive dysfunction and biochemical abnormalities using proton magnetic resonance spectroscopy (¹H-MRS) have been reported in bipolar disorder (BD). Much less is known about the information from BD with suicidal ideation (SI). This study aimed to assess alterations of execution function and biochemical metabolism in BD with SI, in BD without SI, and in healthy controls. The associations between execution function and biochemical metabolism in the two BD patient groups were also been studied.

METHODS

92 patients with bipolar disorder during a depressive episode (50 with current SI, and 42 without SI), as well as, 43 healthy controls were recruited in our study. Executive function was assessed by Wisconsin Card Sorting Test (WCST). Bilateral metabolite levels of prefrontal cortex (PFC), anterior cingulated cortex (ACC), lenticular nucleus (LN) of basal ganglia and thalamus were obtained by ¹H-MRS at 3.0 T, then determined the ratios of N-acetyl aspartate (NAA), choline-containing compounds (Cho), myo-inositol (mI) to creatine (Cr).

RESULTS

Number of categories completed (CC) in BD with SI was significantly less than healthy controls. NAA/Cr ratios of left PFC in the two BD patient groups (with or without SI) were significantly lower than healthy controls, and NAA/Cr ratios of left thalamus were significantly higher than healthy controls. Moreover, NAA/Cr ratio of right LN in BD without SI was higher than BD with SI and healthy controls. For BD with SI, NAA/Cr ratio of left thalamus was negatively correlated with number of CC.

CONCLUSIONS

These results suggested that BD with or without SI may have abnormal NAA metabolism, and NAA/Cr ratio of right LN may distinguish SI from the BD patients. Further, BD with SI may have executive function impairment, which may be associated with the abnormal NAA metabolism in the left thalamus.

Predicting the Development of Normal-Appearing White Matter With Radiomics in the Aging Brain: A Longitudinal Clinical Study

Background: Normal-appearing white matter (NAWM) refers to the normal, yet diseased tissue around the white matter hyperintensities (WMH) on conventional MR images. Radiomics is an emerging quantitative imaging technique that provides more details than a traditional visual analysis. This study aims to explore whether WMH could be predicted during the early stages of NAWM, using a textural analysis in the general elderly population.

Methods: Imaging data were obtained from PACS between 2012 and 2017. The subjects (≥60 years) received two or more MRI exams on the same scanner with time intervals of more than 1 year. By comparing the baseline and follow-up images, patients with noted progression of WMH were included as the case group (n = 51), while age-matched subjects without WMH were included as the control group (n = 51). Segmentations of the regions of interest (ROIs) were done with the ITK software. Two ROIs of developing NAWM (dNAWM) and non-developing NAWM (non-dNAWM) were drawn separately on the FLAIR images of each patient. dNAWM appeared normal on the baseline images, yet evolved into WMH on the follow-up images. Non-dNAWM appeared normal on both the baseline and follow-up images. A third ROI of normal white matter (NWM) was extracted from the control group, which was normal on both baseline and follow-up images. Textural features were dimensionally reduced with ANOVA+MW, correlation analysis, and LASSO. Three models were built based on the optimal parameters of dimensional reduction, including Model 1 (NWM vs. dNAWM), Model 2 (non-dNAWM vs. dNAWM), and Model 3 (NWM vs. non-dNAWM). The ROC curve was adopted to evaluate the classification validity of these models.

Results: Basic characteristics of the patients and controls showed no significant differences. The AUC of Model 1 in training and test groups were 0.967 (95% CI: 0.831–0.999) and 0.954 (95% CI: 0.876–0.989), respectively. The AUC of Model 2 were 0.939 (95% CI: 0.856–0.982) and 0.846 (95% CI: 0.671–0.950). The AUC of Model 3 were 0.713 (95% CI: 0.593–0.814) and 0.667 (95% CI: 0.475–0.825).

Conclusion: Radiomics textural analysis can distinguish dNAWM from non-dNAWM on FLAIR images, which could be used for the early detection of NAWM lesions before they develop into visible WHM.

Texture Analysis of T1-Weighted and Fluid-Attenuated Inversion Recovery Images Detects Abnormalities That Correlate With Cognitive Decline in Small Vessel Disease

Supplemental Digital Content is available in the text.

Background and Purpose—

Magnetic resonance imaging may be useful to assess disease severity in cerebral small vessel disease (SVD), identify those individuals who are most likely to progress to dementia, monitor disease progression, and act as surrogate markers to test new therapies. Texture analysis extracts information on the relationship between signal intensities of neighboring voxels. A potential advantage over techniques, such as diffusion tensor imaging, is that it can be used on clinically obtained magnetic resonance sequences. We determined whether texture parameters (TP) were abnormal in SVD, correlated with cognitive impairment, predicted cognitive decline, or conversion to dementia.

Methods—

In the prospective SCANS study (St George’s Cognition and Neuroimaging in Stroke), we assessed TP in 121 individuals with symptomatic SVD at baseline, 99 of whom attended annual cognitive testing for 5 years. Conversion to dementia was recorded for all subjects during the 5-year period. Texture analysis was performed on fluid-attenuated inversion recovery and T1-weighted images. The TP obtained from the SVD cohort were cross-sectionally compared with 54 age-matched controls scanned on the same magnetic resonance imaging system.

Results—

There were highly significant differences in several TP between SVD cases and controls. Within the SVD population, TP were highly correlated to other magnetic resonance imaging parameters (brain volume, white matter lesion volume, lacune count). TP correlated with executive function and global function at baseline and predicted conversion to dementia, after controlling for age, sex, premorbid intelligence quotient, and magnetic resonance parameters.

Conclusions—

TP, which can be obtained from routine clinical images, are abnormal in SVD, and the degree of abnormality correlates with executive dysfunction and global cognition at baseline and decline during 5 years. TP may be useful to assess disease severity in clinically collected data. This needs testing in data clinically acquired across multiple sites.

Diffusion magnetic resonance imaging in cerebral small vessel disease

Cerebral small vessel disease (SVD) is frequent in the elderly, and accounts for a wide spectrum of clinical and radiological manifestations. This report summarizes the most important findings obtained using diffusion MRI (DWI) in SVD. With DWI and apparent diffusion coefficient (ADC) maps, recent ischemic lesions can easily be detected after acute stroke in SVD, while even multiple simultaneous lesions may be observed. Microstructural changes are frequent in SVD, with increases in diffusivity and decreases in anisotropy being the most reliable findings observed, mainly in white matter. These tissue changes are associated with clinical severity and especially executive dysfunction. They can also precede the usual MRI markers of SVD, such as white matter hyperintensities, microbleeds and lacunes. Thus, DWI may reveal surrogate markers of SVD progression and offer a better understanding of their underlying mechanisms.

Correlation of retinopathy with leukoaraiosis in patients with anterior circulation infarcts

Although retinal and cerebral microvessels share similar embryological, anatomical and physiological characteristics, the correlation between retinopathy and leukoaraiosis (LA), a type of brain microvascular disease, is unclear. In the present study, the sample included 213 patients admitted to the department of neurology from January 2012 through October 2012. MRI and retinal photography were performed within 48hours of hospitalization, and patient demographics, comorbidities, preadmission medications and laboratory data were collected. MRI images were used to divide the patients into LA and non-LA groups. Using multivariate binary logistic regression, the effects of retinopathy on LA were investigated. Of the 213 patients enrolled, 168 were included in this study (LA, n=108; non-LA, n=60). Hypertension, coronary heart disease and carotid artery plaque were more common in the LA group, and these patients showed higher blood levels of C-reactive protein, homocysteine and triglycerides. The incidence of retinopathy was significantly increased in the LA group compared with the non-LA group, and there was a significant correlation between the severity of LA and incidence of retinopathy. Retinopathy is an independent risk factor for LA and can significantly increase the risk of LA when combined with age, coronary heart disease, C-reactive protein, carotid artery plaque or systolic pressure. Taken together, retinopathy is associated with LA in patients with anterior circulation infarcts. Retinopathy is an independent risk factor for LA and an increase the risk of LA, and thus facilitating the evaluation of LA.

Assessment of severity of leukoaraiosis: a diffusional kurtosis imaging study

OBJECTIVE

The objective was to investigate the capabilities of diffusional kurtosis imaging (DKI) in detection of age-related white matter (WM) changes in elderly patients with leukoaraiosis.

MATERIAL AND METHODS

Fractional anisotropy (FA), kurtosis, and diffusion parameters in the frontal lobe and parietal lobe were compared between 14 patients at Fazekas scale 0 and 1, and 15 patients at Fazekas scale 2 and 3.

RESULTS

FA and DKI parameters were significantly altered in the ischemic lesions vs normal regions of WM in the severe patients.

CONCLUSION

DKI can provide sensitive imaging biomarkers for assessing the severity of leukoaraiosis in reference to Fazekas score.

Secondary damage in left-sided frontal white matter detected by diffusion tensor imaging is correlated with executive dysfunction in patients with acute infarction at the ipsilateral posterior corona radiata

BACKGROUND

Executive dysfunction has been observed in patients with left-sided anterior corona radiata infarction. However, whether left-sided posterior corona radiata infarction could cause executive dysfunction is unclear. Also, whether secondary damage in the left frontal white matter following ipsilateral posterior corona radiata infarct is causal or not and contributes to the occurrence and development of executive dysfunction, is still uncertain.

METHODS

Twelve patients with posterior corona radiata infarction underwent diffusion tensor imaging (DTI) and an executive functional assessment at week 1 (W1), week 4 (W4), and week 12 (W12) after onset. Color duplex sonography and Transcranial Duplex Scanning (TCD) were performed at W1 and W12. Twelve healthy volunteers of similar ages and educational histories were examined as controls and assessed once.

RESULTS

In the patients, we observed an increased mean diffusivity (MD) and a decreased fractional anisotropy (FA) in the left frontal white matter from W1 to W12. There were no significant changes in cerebral blood flow in patients between W1 and W12 according to the result of Color duplex sonography and TCD. Patients showed progressively impaired executive function during 12 weeks. Significant correlations were found between increased MD and decreased FA in the left frontal white matter with impaired degree of executive function.

CONCLUSIONS

This study demonstrates that DTI detected secondary damage in left-sided frontal white matter in patients with acute infarction at the ipsilateral posterior corona radiata. This change may be correlated with executive functional changes in these patients.

Regional MRI perfusion measures predict motor/executive function in patients with clinically isolated syndrome

Background. Patients with clinically isolated syndrome (CIS) demonstrate brain hemodynamic changes and also suffer from difficulties in processing speed, memory, and executive functions. Objective. To explore whether brain hemodynamic disturbances in CIS patients correlate with executive functions. Methods. Thirty CIS patients and forty-three healthy subjects, matched for age, gender, education level, and FSIQ, were administered tests of visuomotor learning and set shifting ability. Cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) values were estimated in normal-appearing white matter (NAWM) and normal-appearing deep gray Matter (NADGM) structures, using a perfusion MRI technique. Results. CIS patients showed significantly elevated reaction time (RT) on both tasks, while their CBV and MTT values were globally increased, probably due to inflammatory vasodilation. Significantly, positive correlation coefficients were found between error rates on the inhibition condition of the visuomotor learning task and CBV values in occipital, periventricular NAWM and both thalami. On the set shifting condition of the respective task significant, positive associations were found between error rates and CBV values in the semioval center and periventricular NAWM bilaterally. Conclusion. Impaired executive function in CIS patients correlated positively with elevated regional CBV values thought to reflect inflammatory processes.

Periventricular white matter integrity and cortisol levels in healthy controls and in euthymic patients with bipolar disorder: an exploratory analysis

BACKGROUND

Bipolar disorder is associated with both white matter abnormalities and hypothalamo-pituitary-adrenal axis dysfunction. In a post-hoc analysis of diffusion tensor data, the relationship between cortisol levels and white matter structural integrity was explored in healthy controls and in euthymic patients with bipolar disorder.

METHODS

Healthy control subjects and patients with bipolar disorder, prospectively verified as euthymic, underwent diffusion tensor MRI: fractional anisotropy and mean diffusivity data in fifteen regions of interest were obtained. Morning and evening salivary cortisol levels (SCLs) were measured.

RESULTS

Significant negative partial correlations were found between fractional anisotropy and evening SCLs in control subjects in four periventricular regions. This pattern was absent in bipolar patients, possibly due to the presence of an excess of extracellular fluid manifested as a significant increase in mean diffusivity in those regions.

LIMITATIONS

This is an exploratory, post-hoc analysis of data with relatively small sample sizes. Lithium treatment and past substance abuse in the bipolar group are potentially confounding factors in this study.

CONCLUSIONS

These preliminary data show an inverse relationship between evening cortisol levels and a measure of periventricular white matter integrity in healthy controls. This relationship appears disrupted in bipolar patients, possibly due to periventricular osmoregulatory dysfunction, the effects of medication or past substance use. Future research should further investigate the influences of cortisol on oligodendrocyte function, white matter integrity and brain osmoregulation in bipolar disorder.