Association between white matter alterations and domain-specific cognitive impairment in cerebral small vessel disease: A meta-analysis of diffusion tensor imaging

Temporal changes and implications of diffusion tensor imaging metrics and cerebral white matter volume in patients undergoing carotid endarterectomy - a prospective study

AIMS

To test utility of diffusion MRI-derived indices in carotid endarterectomy (CEA), change of diffusion tensor imaging (DTI) metrics, cerebral white matter (WM) volumes were evaluated and predictors of overall mortality determined.

METHODS

Prospectively enrolled participants had preoperative, immediate and late postoperative DTI after CEA. WM volumes, DTI metrics (fractional anisotropy, FA; axial, radial, mean diffusivities; AD, RD, MD, respectively) were calculated for the index/contralateral hemispheres at all time points. Temporal changes, predictors of log2-transformed WM volumes, DTI values were analyzed using linear mixed model. Uni- and multivariable Cox proportional hazards models were used to identify predictors of mortality.

RESULTS

60 subjects (57% male, 69.5 ± 7.2years) were included. Significantly increased AD and MD was observed in both hemispheres comparing the preoperative and immediate postoperative DTI metrics (index AD: β = 0.02 [95%CI:0.01,0.02], p < 0.001; index MD: β = 0.02 [95%CI:0.01,0.03], p < 0.001; contralateral AD: β = 0.01 [95%CI:0.01,0.02], p = 0.001; contralateral MD: β = 0.02 [95%CI:0.01,0.03], p = 0.003). The index MD decreased (β = 0.01 [95%CI:0.01,0.001], p = 0.04), bilateral WM volumes (index WM: β = 0.04 [95%CI:0.02,0.07], p < 0.001; contralateral WM: β = 0.05 [95%CI:0.03,0.07], p < 0.001) decreased significantly between the immediate and late postoperative scans. Postoperative contralateral FA correlated significantly with lower mortality (HR = 0.001 [95%CI:0.001,0.19], p = 0.02); postoperative contralateral RD (HR = 3.74 × 104 [95%CI:1.62,8.60 × 108], p = 0.04) and MD (HR = 1.19 × 105 [95%CI:1.03,1.37 × 1010], p = 0.049) were significant predictors of mortality.

CONCLUSION

The increase of various DTI metrics from pre-to-postoperative may be indicative of microstructural deterioration following CEA. Temporal changes between the immediate and late postoperative scans suggest, however, reversal of detrimental WM changes and clearance of presumed subclinical WM edema. Our results also imply, that preserved cerebral properties are protective after CEA.

Retinal assessment in 143 patients with white matter lesions: the potential of OCTA as an evaluation tool

Background

The retina is a simple window to reflect the changes of brain nerves. The aim of this study was to investigate the association between retinal status and white matter lesions (WMLs) in 143 patients aged 50-80 years, utilizing Optical Coherence Tomography Angiography (OCTA) and the Fazekas Visual Scale for assessment.

Methods

A total of 143 subjects underwent MRI scanning to assess the degree of WMLs using the Fazekas scale. Retinal imaging was conducted utilizing OCTA. Multivariate logistic regression analysis was employed to determine the odds ratios and 95% confidence intervals associated with the Fazekas score for each factor. The relationship between cognitive function and various OCTA parameters was assessed using quadratic and cubic simulation curve models. Data following a normal distribution are presented as means, while non-normally distributed data are reported as medians. Qualitative data are expressed as percentages.

Results

As Fazekas grades increased, ILM-IPL thickness (OR = 3.267, OR = 8.436), vessel density in the parafoveal region of the macula, retinal vessel densities (OR = 2.058, OR = 2.363), and RNFL thickness significantly reduced (p < 0.05). With increasing Fazekas scores, the bilateral foveal avascular zone showed a significant increase (OR = 0.362, OR = 0.458) (p < 0.05). Retinal thickness and vascular density were negatively correlated with WMLs, and positively correlated with cognitive function (p < 0.05).

Conclusion

The severity of WMLs increases as retinal thickness and vascular density decrease. OCTA examination has a degree of role in screening for WMLs caused by cerebral microvascular disease. Its effectiveness in screening early asymptomatic individuals or those with mild cognitive impairment is somewhat limited.

White Matter Hyperintensities and Cognitive Functions in People With the R544C Variant of the NOTCH3 Gene Without Stroke or Dementia

BACKGROUND AND OBJECTIVES

NOTCH3 pathologic variants cause cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), which presents with stroke and dementia and is characterized by white matter hyperintensities (WMHs) on brain MRI. The R544C variant is a common pathologic variant in Taiwan, but not all carriers exhibit significant symptoms. We investigated whether WMHs occur before clinical symptoms in carriers with pathogenic variants, examined factors associated with WMHs, and explored their relationship with cognitive functions.

METHODS

We enrolled 63 R544C carriers without overt clinical disease (WOCD) and 37 age-matched and sex-matched noncarriers as controls from the Taiwan Precision Medicine Initiative data set. All participants underwent clinical interviews, comprehensive neuropsychological assessments, and brain MRI. We calculated total and regional WMH volumes, determined the age at which WMHs began increasing in carriers, and examined the relationship between WMHs and neuropsychological performance. Factors associated with WMH volumes were analyzed using multivariable linear regression models.

RESULTS

Compared with controls, R544C carriers WOCD had increased WMH volume, except in the occipital and midbrain areas, and showed a rapid increase in WMHs starting at age 48. They scored lower on the Mini-Mental State Examination (median = 28.4 vs 29.0, p = 0.048), Montreal Cognitive Assessment (MoCA) (median = 28.3 vs 29.0, p = 0.013), and memory and executive function tests than controls. After adjusting for age, sex, and education, MoCA scores were associated with whole-brain (r = -0.387, padj = 0.008) and regional WMHs (all padj < 0.05) except in the midbrain area. Age (β = 0.034, 95% CI 0.021-0.046, p < 0.001), hypercholesterolemia (β = 0.375, 95% CI 0.097-0.653, p = 0.009), and the vascular risk factor (VRF) index (β = 0.132, 95% CI 0.032-0.242, p = 0.019) were associated with the WMH severity in carriers.

DISCUSSION

Our study revealed that WMHs are extensively distributed in R544C carriers WOCD. They exhibited a rapid increase in WMHs beginning at age 48, approximately 7 years earlier than the reported age at symptomatic onset. Age was the strongest predictive factor of WMHs, and VRF, particularly hypercholesterolemia, might be modifying factors of WMHs.

Diffusion tensor imaging in cerebral small vessel disease applications: opportunities and challenges

Cerebral small vessel disease (CSVD) is a syndrome of pathology, imaging, and clinical manifestations caused primarily by a variety of functional or structural lesions in the small blood vessels of the brain. CSVD contributes to approximately 45% of dementia and 25% of ischemic strokes worldwide and is one of the most important causes of disability. The disease progresses insidiously, and patients often have no typical symptoms in the early stages, but have an increased risk of stroke, death, and poor long-term prognosis. Therefore, early diagnosis of CSVD is particularly important. Neuroimaging is the most important diagnostic tool used for CSVD. Therefore, it is important to explore the imaging mechanisms of CSVD for its early diagnosis and precise treatment. In this article, we review the principles and analysis methods of DTI, analyze the latest DTI studies on CSVD, clarify the disease-lesion mapping relationships between cerebral white matter (WM) microstructural damage and CSVD, explore the pathogenic mechanisms and preclinical imaging features of CSVD, and summarize the latest research directions of CSVD and research methods to provide a comprehensive and objective imaging basis for the diagnosis and treatment of CSVD.

Intermittent theta-burst stimulation alleviates hypoxia-ischemia-caused myelin damage and neurologic disability

Neonatal hypoxia-ischemia (HI) results in behavioral deficits, characterized by neuronal injury and retarded myelin formation. To date, limited treatment methods are available to prevent or alleviate neurologic sequelae of HI. Intermittent theta-burst stimulation (iTBS), a non-invasive therapeutic procedure, is considered a promising therapeutic tool for treating some neurocognitive disorders and neuropsychiatric diseases. Hence, this study aims to investigate whether iTBS can prevent the negative behavioral manifestations of HI and explore the mechanisms for associations. We exposed postnatal day 10 Sprague-Dawley male and female rats to 2 h of hypoxia (6% O2) following right common carotid artery ligation, resulting in oligodendrocyte (OL) dysfunction, including reduced proliferation and differentiation of oligodendrocyte precursor cells (OPCs), decreased OL survival, and compromised myelin in the corpus callosum (CC) and hippocampal dentate gyrus (DG). These alterations were concomitant with cognitive dysfunction and depression-like behaviors. Crucially, early iTBS treatment (15 G, 190 s, seven days, initiated one day post-HI) significantly alleviated HI-caused myelin damage and mitigated the neurologic sequelae both in male and female rats. However, the late iTBS treatment (initiated 18 days after HI insult) could not significantly impact these behavioral deficits. In summary, our findings support that early iTBS treatment may be a promising strategy to improve HI-induced neurologic disability. The underlying mechanisms of iTBS treatment are associated with promoting the differentiation of OPCs and alleviating myelin damage.

Memory deficit in patients with cerebral small vessel disease: evidence from eye tracking technology

Cerebral small vessel disease is the one of the most prevalent causes of vascular cognitive impairment. We aimed to find objective and process-based indicators related to memory function to assist in the detection of memory impairment in patients with cerebral small vessel disease. Thirty-nine cerebral small vessel disease patients and 22 healthy controls were invited to complete neurological examinations, neuropsychological assessments, and eye tracking tasks. Eye tracking indicators were recorded and analyzed in combination with imaging features. The cerebral small vessel disease patients scored lower on traditional memory task and performed worse on eye tracking memory task performance compared to the healthy controls. The cerebral small vessel disease patients exhibited longer visit duration and more visit count within areas of interest and targets and decreased percentage value of total visit duration on target images to total visit duration on areas of interest during decoding stage among all levels. Our results demonstrated the cerebral small vessel disease patients performed worse in memory scale and eye tracking memory task, potentially due to their heightened attentional allocation to nontarget images during the retrieval stage. The eye tracking memory task could provide process-based indicators to be a beneficial complement to memory assessment and new insights into mechanism of memory impairment in cerebral small vessel disease patients.