The genetics of white matter lesions

White matter lesions contribute to motor and non-motor disorders in Parkinson's disease: a critical review

Parkinson's disease (PD) is a prevalent neurodegenerative disease, characterized by movement disorders and non-motor symptoms like cognitive impairment and depression. Degeneration of dopaminergic neurons in the substantia nigra and Lewy bodies have long been considered as main neuropathological changes. However, recent magnetic resonance imaging (MRI) studies have shown that white matter lesions (WMLs) were present in PD patients. WMLs are characterized by loss or impairment of myelin sheath in central nerve fibers, which are closely correlated with motor and cognitive dysfunction in PD. WMLs alterations precede nigrostriatal neuronal losses and can independently affect the clinical severity or characteristics of motor coordination in PD patients. Currently, the exact mechanism of WMLs involvement in the occurrence and development of PD remains unclear. It is speculated that WMLs may participate in the pathogenesis of PD by disrupting important connections in brain or promoting axonal degeneration. In this review, we will discuss the pathological changes and mechanisms of WMLs, elaborate the impact of WMLs on the progression of PD, clarify the importance of WMLs in PD pathogenesis, and thus provide novel targets for PD treatments.

CADASIL: A NOTCH3-associated cerebral small vessel disease

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common hereditary cerebral small vessel disease (CSVD), pathologically characterized by a non-atherosclerotic and non-amyloid diffuse angiopathy primarily involving small to medium-sized penetrating arteries and leptomeningeal arteries. In 1996, mutation in the notch receptor 3 gene (NOTCH3) was identified as the cause of CADASIL. However, since that time other genetic CSVDs have been described, including the HtrA serine peptidase 1 gene-associated CSVD and the cathepsin A gene-associated CSVD, that clinically mimic the original phenotype. Though NOTCH3-associated CSVD is now a well-recognized hereditary disorder and the number of studies investigating this disease is increasing, the role of NOTCH3 in the pathogenesis of CADASIL remains elusive.

AIM OF REVIEW

This review aims to provide insights into the pathogenesis and the diagnosis of hereditary CSVDs, as well as personalized therapy, predictive approach, and targeted prevention. In this review, we summarize the current progress in CADASIL, including the clinical, neuroimaging, pathological, genetic, diagnostic, and therapeutic aspects, as well as differential diagnosis, in which the role of NOTCH3 mutations is highlighted.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, CADASIL is revisited as a NOTCH3-associated CSVD along with other hereditary CSVDs.

Differential associations between abnormal cardiac left ventricular geometry types and cerebral white matter disease

OBJECTIVES

Reduced cardiac outflow due to left ventricular hypertrophy has been suggested as a potential risk factor for development of cerebral white matter disease. Our study aimed to examine the correlation between left ventricular geometry and white matter disease volume to establish a clearer understanding of their relationship, as it is currently not well-established.

METHODS

Consecutive patients from 2016 to 2021 who were ≥18 years and underwent echocardiography, cardiac MRI, and brain MRI within one year were included. Four categories of left ventricular geometry were defined based on left ventricular mass index and relative wall thickness on echocardiography. White matter disease volume was quantified using an automated algorithm applied to axial T2 FLAIR images and compared across left ventricular geometry categories.

RESULTS

We identified 112 patients of which 34.8 % had normal left ventricular geometry, 20.5 % had eccentric hypertrophy, 21.4 % had concentric remodeling, and 23.2 % had concentric hypertrophy. White matter disease volume was highest in patients with concentric hypertrophy and concentric remodeling, compared to eccentric hypertrophy and normal morphology with a trend-P value of 0.028. Patients with higher relative wall thickness had higher white matter disease volume (10.73 ± 10.29 cc vs 5.89 ± 6.46 cc, P = 0.003), compared to those with normal relative wall thickness.

CONCLUSION

Our results showed that abnormal left ventricular geometry is associated with higher white matter disease burden, particularly among those with abnormal relative wall thickness. Future studies are needed to explore causative relationships and potential therapeutic options that may mediate the adverse left ventricular remodeling and its effect in slowing white matter disease progression.

Genetic and Environmental Effects on the Development of White Matter Hyperintensities in a Middle Age Twin Population

Introduction: White matter hyperintensities (WMH) indicate white matter brain lesions in magnetic resonance imaging (MRI), which can be used as a marker for brain aging and cerebrovascular and neurodegenerative disorders. Twin studies revealed substantial but not uniform WMH heritability in elderly twins. The objective of our study was to investigate the genetic and environmental components of WMH, as well as their importance in a healthy twin population, utilizing 3T MRI scanners in a middle-aged twin population. Methods: Brain MRI was performed on 120 healthy adult twins from the Hungarian Twin Registry on a 3T scanner (86 monozygotic, MZ and 34 dizygotic, DZ twins; median age 50 ± 26.5 years, 72.5% female and 27.5% male). The count of WMH on FLAIR images was calculated using an automated volumetry pipeline (volBrain) and human processing. The age- and sex-adjusted MZ and DZ intra-pair correlations were determined and the total variance was decomposed into genetic, shared and unique environmental components using structural equation modeling. Results: Age and sex-adjusted MZ intrapair correlations were higher than DZ correlations, indicating moderate genetic influence in each lesion (rMZ = 0.466, rDZ = −0.025 for total count; rMZ = 0.482, rDZ = 0.093 for deep white matter count; rMZ = 0.739, rDZ = 0.39 for infratentorial count; rMZ = 0.573, rDZ = 0.372 for cerebellar count and rMZ = 0.473, rDZ = 0.19 for periventricular count), indicating a moderate heritability (A = 40.3%, A = 45%, A = 72.7% and A = 55.5%and 47.2%, respectively). The rest of the variance was influenced by unique environmental effects (E between 27.3% and 59.7%, respectively). Conclusions: The number of WMH lesions is moderately influenced by genetic effects, particularly in the infratentorial region in middle-aged twins. These results suggest that the distribution of WMH in various brain regions is heterogeneous.

Neuroimaging Pearls from the MDS Congress Video Challenge. Part 1: Genetic Disorders

We selected several "imaging pearls" presented during the Movement Disorder Society (MDS) Video Challenge for this review. While the event, as implicated by its name, was video-centered, we would like to emphasize the important role of imaging in making the correct diagnosis. We divided this anthology into two parts: genetic and acquired disorders. Genetic cases described herein were organized by the inheritance pattern and the focus was put on the imaging findings and differential diagnoses. Despite the overlapping phenotypes, certain described disorders have pathognomonic MRI brain findings that would provide either the "spot" diagnosis or result in further investigations leading to the diagnosis. Despite this, the diagnosis is often challenging with a broad differential diagnosis, and hallmark findings may be present for only a limited time.

White matter integrity correlates with cognition and disease severity in Fabry disease

Cerebral white matter pathology is a common CNS manifestation of Fabry disease, visualized as white matter hyperintensities on MRI in 42-81% of patients. Diffusion tensor imaging (DTI) MRI is a sensitive technique to quantify microstructural damage within the white matter with potential value as a disease biomarker. We evaluated the pattern of DTI abnormalities in Fabry disease, and their correlations with cognitive impairment, mood, anxiety, disease severity and plasma lyso-Gb3 levels in 31 patients with genetically proven Fabry disease and 19 age-matched healthy control subjects. We obtained average values of fractional anisotropy and mean diffusivity within the white matter and performed voxelwise analysis with tract-based spatial statistics. Using a standardized neuropsychological test battery, we assessed processing speed, executive function, anxiety, depression and disease severity. The mean age (% male) was 44.1 (45%) for patients with Fabry disease and 37.4 (53%) for the healthy control group. In patients with Fabry disease, compared to healthy controls the mean average white matter fractional anisotropy was lower in [0.423 (standard deviation, SD 0.023) versus 0.446 (SD 0.016), P = 0.002] while mean average white matter mean diffusivity was higher (749 × 10-6 mm2/s (SD 32 × 10-6) versus 720 × 10-6 mm2/s (SD 21 × 10-6), P = 0.004]. Voxelwise statistics showed that the diffusion abnormalities for both fractional anisotropy and mean diffusivity were anatomically widespread. A lesion probability map showed that white matter hyperintensities also had a wide anatomical distribution with a predilection for the posterior centrum semiovale. However, diffusion abnormalities in Fabry disease were not restricted to lesional tissue; compared to healthy controls, the normal appearing white matter in patients with Fabry disease had reduced fractional anisotropy [0.422 (SD 0.022) versus 0.443 (SD 0.017) P = 0.003] and increased mean diffusivity [747 × 10-6 mm2/s (SD 26 × 10-6) versus 723 × 10-6 mm2/s (SD 22 × 10-6), P = 0.008]. Within patients, average white matter fractional anisotropy and white matter lesion volume showed statistically significant correlations with Digit Symbol Coding Test score (r = 0.558, P = 0.001; and r = -0.633, P ≤ 0.001, respectively). Average white matter fractional anisotropy correlated with the overall Mainz Severity Score Index (r = -0.661, P ≤ 0.001), while average white matter mean diffusivity showed a strong correlation with plasma lyso-Gb3 levels (r = 0.559, P = 0.001). Our findings using DTI confirm widespread areas of microstructural white matter disruption in Fabry disease, extending beyond white matter hyperintensities seen on conventional MRI. Moreover, diffusion measures show strong correlations with cognition (processing speed), clinical disease severity and a putative plasma biomarker of disease activity, making them promising quantitative biomarkers for monitoring Fabry disease severity and progression.

Integrated analysis of microRNA and mRNA expression profiling identifies BAIAP3 as a novel target of dysregulated hsa-miR-1972 in age-related white matter lesions

White matter lesions known as leukoaraiosis (LA) are cerebral white matter hyperintensities observed in elderly individuals. Currently, no reliable molecular biomarkers are available for monitoring their progression over time. To identify biomarkers for the onset and progression of LA, we analyzed whole blood-based, microRNA expression profiles of leukoaraiosis, validated those exhibiting significant microRNA changes in clinical subjects by means of quantitative real-time polymerase chain reactions and determined the function of miRNA in cell lines by means of microRNA mimic transfection assays. A total of seven microRNAs were found to be significantly down-regulated in leukoaraiosis. Among the microRNAs, hsa-miR-1972 was downregulated during the early onset phase of leukoaraiosis, as confirmed in independent patients, and it was found to target leukoaraiosis-dependent BAIAP3, decreasing its expression in 293T cell lines. Functional enrichment analysis revealed that significantly dysregulated miRNAs-mRNAs changes associated with the onset of leukoaraiosis were involved in neurogenesis, neuronal development, and differentiation. Taken together, the study identified a set of candidate microRNA biomarkers that may usefully monitor the onset and progression of leukoaraiosis. Given the enrichment of leukoaraiosis-associated microRNAs and mRNAs in neuron part and membrane system, BAIAP3 could potentially represent a novel target of hsa-miR-1972 in leukoaraiosis through which microRNAs are involved in the pathogenesis of white matter lesions.

Vascular depression for radiology: A review of the construct, methodology, and diagnosis

Vascular depression (VD) as defined by magnetic resonance imaging (MRI) has been proposed as a unique subtype of late-life depression. The VD hypothesis posits that cerebrovascular disease, as characterized by the presence of MRI-defined white matter hyperintensities, contributes to and increases the risk for depression in older adults. VD is also accompanied by cognitive impairment and poor antidepressant treatment response. The VD diagnosis relies on MRI findings and yet this clinical entity is largely unfamiliar to neuroradiologists and is rarely, if ever, discussed in radiology journals. The primary purpose of this review is to introduce the MRI-defined VD construct to the neuroradiology community. Case reports are highlighted in order to illustrate the profile of VD in terms of radiological, clinical, and neuropsychological findings. A secondary purpose is to elucidate and elaborate on the measurement of cerebrovascular disease through visual rating scales and semi- and fully-automated volumetric methods. These methods are crucial for determining whether lesion burden or lesion severity is the dominant pathological contributor to VD. Additionally, these rating methods have implications for the growing field of computer assisted diagnosis. Since VD has been found to have a profile that is distinct from other types of late-life depression, neuroradiologists, in conjunction with psychiatrists and psychologists, should consider VD in diagnosis and treatment planning.

The Associations of PMF1, ICAM1, AGT, TRIM65, FBF1, and ACOX1 Variants With Leukoaraiosis in Chinese Population

Background: Leukoaraiosis (LA) is shown as white matter hyperintensities on T2-weighted magnetic resonance imaging brain scans. Together with candidate gene association studies (CGAS), multiple genome-wide association studies (GWAS) have reported large numbers of single nucleotide polymorphisms (SNPs) to be associated with LA in European populations. To date, no replication studies have been reported in independent Chinese samples.

Methods: Here, we performed a candidate gene association study comprising 220 Chinese subjects with LA and 50 controls. Thirty-nine polymorphisms on 32 risk genes were selected from previous studies, and they were genotyped through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Genetic association analysis was firstly performed in all subjects with LA. Then, the same analysis was conducted in the six random sampling cohorts of 50 LA patients, respectively. Data analyses on the associations of SNPs with LA risk were evaluated through Pearson’s χ² and multivariate logistic regression tests.

Results: We found that eight polymorphisms in six genes (PMF1, ICAM1, TRIM65, AGT, FBF1, and ACOX1) were significantly associated with LA in the genetic association tests. Except for those eight gene variants, 24 other polymorphisms were not found to be significantly associated with LA in general genetic model, dominant model, recessive model, or multiplicative model. Among those eight polymorphisms, rs2984613 in PMF1 showed significant association with LA in the cohort of 220 LA subjects, and such significant association remained in both general genetic model (OR: 0.262, 95% CI: 0.091–0.752, p_adj = 0.030) and recessive model (OR: 0.323, 95% CI: 0.119–0.881, p_adj = 0.038) when controlling for clinical variables. Seven other significant variants (rs5498 in ICAM1, rs699 in AGT, rs2305913 in FBF1, rs1135640 in ACOX1, and rs3760128, rs7214628, and rs7222757 in TRIM65) were identified in those six random sampling tests that were conducted in the adjusted cohorts of 50 LA patients. In addition, except for rs699 which showed detrimental effect and represented a risk variant for LA, seven other polymorphisms seemed to exert protective effects on LA and to reduce the risk of LA. It is necessary to confirm these associations in an independent cohort.

Conclusions: This first replication study on multiple genes in an independent Chinese population did not replicate any risk polymorphisms for LA other than rs 699 in AGT but revealed the significantly negative associations of PMF1, ICAM1, TRIM65, FBF1, and ACOX1 polymorphisms with LA. It not only supported the strong ethnic differences in the genetics of LA but also indicated that those six identified genes may be involved in Chinese white matter lesions. Larger scales of CGAS and GWAS are necessary to confirm and decipher those ethnic-Han specific risk genes for LA in China.

Retinal and Cerebral Microvasculopathy: Relationships and Their Genetic Contributions

Purpose

Retinal microvasculopathy may reflect small vessel disease in the brain. Here we test the relationships between retinal vascular parameters and small vessel disease, the influence of cardiovascular risk factors on these relationships, and their common genetic background in a monozygotic twin cohort.

Methods

We selected 134 cognitively healthy individuals (67 monozygotic twin pairs) aged ≥60 years from the Netherlands Twin Register for the EMIF-AD PreclinAD study. We measured seven retinal vascular parameters averaged over both eyes using fundus images analyzed with Singapore I Vessel Assessment. Small vessel disease was assessed on MRI by a volumetric measurement of periventricular and deep white matter hyperintensities. We calculated associations between RVPs and WMH, estimated intratwin pair correlations, and performed twin-specific analyses on relationships of interest.

Results

Deep white matter hyperintensities volume was positively associated with retinal tortuosity in veins (P = 0.004) and fractal dimension in arteries (P = 0.001) and veins (P = 0.032), periventricular white matter hyperintensities volume was positively associated with retinal venous width (P = 0.028). Intratwin pair correlations were moderate to high for all small vessel disease/retinal vascular parameter variables (r = 0.49-0.87, P < 0.001). Cross-twin cross-trait analyses showed that retinal venous tortuosity of twin 1 could predict deep white matter hyperintensities volume of the co-twin (r = 0.23, P = 0.030). Within twin-pair differences for retinal venous tortuosity were associated with within twin-pair differences in deep white matter hyperintensities volume (r = 0.39, P = 0.001).

Conclusions

Retinal arterial fractal dimension and venous tortuosity have associations with deep white matter hyperintensities volume. Twin-specific analyses suggest that retinal venous tortuosity and deep white matter hyperintensities volume have a common etiology driven by both shared genetic factors and unique environmental factors, supporting the robustness of this relationship.

Advances in biomarkers of cerebral small vessel disease

Cerebral small vessel disease (CSVD) refers to a type of syndrome caused by lesions in perforating arteries, small veins, small arteries, or capillaries, resulting in clinical, imaging, or pathological alterations. The occurrence and development of CSVD are related to various cerebrovascular risk factors, such as metabolism and genetic factors. CSVD is diagnosed based on brain imaging biomarkers; however, biomarkers capable of predicting and diagnosing CSVD early in its progression have not been found. Exploring biomarkers closely related to disease progression is of great significance for early diagnosis, prognosis, prevention, and treatment of CSVD. This article examines the research progress of CSVD biomarkers, from inflammatory biomarkers, coagulation and fibrinolysis markers, biomarkers of endothelial dysfunction, biomarkers related to cerebrospinal fluid, and gene markers.

Incidence and risk factors of leukoaraiosis from 4683 hospitalized patients: A cross-sectional study

Leukoaraiosis (LA) refers to white matter hyperintensities or white matter lesions (WMLs) on magnetic resonance imaging (MRI) scans of the brain; this disease is associated with an increased risk of stroke, dementia, and cognitive decline. The aims of the study are to assess the incidence of LA and its associated risk factors in a Chinese population.A hospital-based cross-sectional study was conducted that included 4683 patients who were 40 years or older. Data collected included age, sex, hypertension, diabetes, smoking, drinking, homocysteine (HCY), and low-density lipoprotein cholesterol (LDL-C) levels in the blood in addition to brain MRI information. We examined the relationship of those putative risk factors with LA, LA occurrence, and LA progression through single-factor and multivariate analyses.Of the total subjects, 58.3% (2731/4683 cases) suffered from LA. LA was more frequent amongst elderly females, particularly in those older than 60, compared to men. The incidence of LA increased with age. Age, sex, hypertension, diabetes, smoking, and HCY levels all were risk factors for LA. Amongst those risk factors, both smoking and high HCY levels were associated with the onset process of LA. Moreover, the multivariate logistic analysis revealed that both drinking and abnormal LDL-C levels were positive regulators in the progression process of LA.This study revealed that the incidence of LA is high in hospitalized patients in China; moreover, age, sex, hypertension, diabetes mellitus, smoking, drinking, and abnormal HCY and LDL-C levels were found to be associated with overall LA risk, LA onset, or LA progression. These results provide insight into strategies for the prevention and treatment of LA.

MCP-1-mediated activation of microglia promotes white matter lesions and cognitive deficits by chronic cerebral hypoperfusion in mice

Microglia activation played a vital role in the pathogenesis of white matter lesions (WMLs) by chronic cerebral hypoperfusion. In addition, hypoxia induced up-regulated expression of MCP-1, promotes the activation of microglia. However, the role of MCP-1-mediated microglia activation in chronic cerebral ischemia is still unknown. To explore that, chronic cerebral hypoperfusion model was established by permanent stenosis of bilateral common carotid artery in mice. The activation of microglia and the related signal pathway p38MAPK/PKC in white matter, and working memory of mice were observed. We found that stenosis of common carotid arteries could induce MCP-1-mediated activation of microglia through p38MAPK/PKC pathway and white matter lesions. Taken together, our findings represent a novel mechanism of MCP-1 involved in activation of microglia and provide a novel therapeutical strategy for chronic cerebral hypoperfusion.

Analysis of genetic polymorphisms associated with leukoaraiosis in the southern Chinese population: A case-control study

Leukoaraiosis (LA) is a frequent neuroimaging finding commonly observed on brain MRIs of elderly people with prevalence ranging from 50% to 100%. Multiple susceptibility genes or genetic risk factors for LA have been identified in subjects of European descent. Here, we report the first replication study on several common and novel genetic variations in the Chinese population. In this study, a total of 244 subjects (201 LA patients and 43 controls) were enrolled according to our new and strict definition for LA. Subsequently, 6 genetic variants at 5 genes, rs3744028 in TRIM65, rs1055129 in TRIM47, rs1135889 in FBF1, rs1052053 in PMF1, and rs1801133 (C677T) and rs1801131(A1298C) in MTHFR, were selected for genotyping using polymerase chain reaction (PCR)-based pyrosequencing and restriction fragment length polymorphism (RFLP) together with capillary electrophoresis (CE) and agarose gel electrophoresis. Finally, Pearson's χ and multivariate logistic regression tests were used to examine the associations between the genotypes and LA. Among these candidate polymorphisms, except for rs1052053 and rs1801131, rs1135889 (P = 0.012) showed significant associations with LA in the dominant model, and the other 3 SNPs, rs3744028 (P = 0.043), rs1055129 (P = 0.038), and rs1801133 (P = 0.027), showed significant associations with LA in the recessive model. However, these differences no longer remained significant after adjusting for age, gender, hypertension, and diabetes mellitus and applying Bonferroni correction or Sidak correction for multiple testing. These results suggest that the above-mentioned genetic variants are not associated with LA risk. In summary, the study did not replicate the susceptibility of rs3744028, rs1055129, and rs1135889 at the Chr17q25 locus for LA nor did it find any other significant results for rs1052053, rs1801133, and rs1801131 in the Chinese population. It strongly indicated the ethnic differences in the genetics of LA. However, the associations of rs3744028 (TRIM65), rs1055129 (TRIM47), rs1135889 (FBF1), and rs1801133 (MTHFR) with LA before Bonferroni correction and Sidak correction for multiple testing are worth highlighting. Thus, we believe that a genome-wide association study and candidate gene association studies are needed to reassess the previous findings and screen novel risk genes for LA in China.

White Matter Hyperintensities Are Under Strong Genetic Influence

BACKGROUND AND PURPOSE

The genetic basis of white matter hyperintensities (WMH) is still unknown. This study examines the heritability of WMH in both sexes and in different brain regions, and the influence of age.

METHODS

Participants from the Older Australian Twins Study were recruited (n=320; 92 monozygotic and 68 dizygotic pairs) who volunteered for magnetic resonance imaging scans and medical assessments. Heritability, that is, the ratio of the additive genetic variance to the total phenotypic variance, was estimated using the twin design.

RESULTS

Heritability was high for total WMH volume (0.76), and for periventricular WMH (0.64) and deep WMH (0.77), and varied from 0.18 for the cerebellum to 0.76 for the occipital lobe. The genetic correlation between deep and periventricular WMH regions was 0.85, with one additive genetics factor accounting for most of the shared variance. Heritability was consistently higher in women in the cerebral regions. Heritability in deep but not periventricular WMH declined with age, in particular after the age of 75.

CONCLUSIONS

WMH have a strong genetic influence but this is not uniform through the brain, being higher for deep than periventricular WMH and in the cerebral regions. The genetic influence is higher in women, and there is an age-related decline, most markedly for deep WMH. The data suggest some heterogeneity in the pathogenesis of WMH for different brain regions and for men and women.

Candidate-gene analysis of white matter hyperintensities on neuroimaging

BACKGROUND

White matter hyperintensities (WMH) are a common radiographic finding and may be a useful endophenotype for small vessel diseases. Given high heritability of WMH, we hypothesised that certain genotypes may predispose individuals to these lesions and consequently, to an increased risk of stroke, dementia and death. We performed a meta-analysis of studies investigating candidate genes and WMH to elucidate the genetic susceptibility to WMH and tested associated variants in a new independent WMH cohort. We assessed a causal relationship of WMH to methylene tetrahydrofolate reductase (MTHFR).

METHODS

Database searches through March 2014 were undertaken and studies investigating candidate genes in WMH were assessed. Associated variants were tested in a new independent ischaemic cohort of 1202 WMH patients. Mendelian randomization was undertaken to assess a causal relationship between WMH and MTHFR.

RESULTS

We identified 43 case-control studies interrogating eight polymorphisms in seven genes covering 6,314 WMH cases and 15,461 controls. Fixed-effects meta-analysis found that the C-allele containing genotypes of the aldosterone synthase CYP11B2 T(-344)C gene polymorphism were associated with a decreased risk of WMH (OR=0.61; 95% CI, 0.44 to 0.84; p=0.003). Using mendelian randomisation the association among MTHFR C677T, homocysteine levels and WMH, approached, but did not reach, significance (expected OR=1.75; 95% CI, 0.90-3.41; observed OR=1.68; 95% CI, 0.97-2.94). Neither CYP11B2 T(-344)C nor MTHFR C677T were significantly associated when tested in a new independent cohort of 1202 patients with WMH.

CONCLUSIONS

There is a genetic basis to WMH but anonymous genome wide and exome studies are more likely to provide novel loci of interest.

Genetic associations of leukoaraiosis indicate pathophysiological mechanisms in white matter lesions etiology

Leukoaraiosis (LA), also called white matter lesions (WMLs) and white matter hyperintensities (WMHs), is a frequent neuroimaging finding commonly seen on magnetic resonance imaging brain scans of elderly people with prevalence ranging from 50% to 100%. Although it remains asymptomatic, LA is not considered to be benign, and it is showed to be related to a host of poor clinical outcomes and increases the risk of disability, dementia, depression, stroke, and the overall morbidity and mortality. Pathologically, LA is characterized by loss of myelin and axons, patchy demyelination, and denudation of ependyma in regions of WMH. Age and hypertension are the most importantly established risk factors for LA. However, the precise pathogenic mechanisms remain unclear. Together with the previous findings, our recent genetic results strongly supported that LA is associated with immune response and neuroinflammation. Therefore, we confidently hypothesized that LA was not only a common neuroimaging phenomenon in the elderly but also an emerging neuroinflammatory disorder in the central nervous system. This article focusing on neuroimaging classification, genetics basis, and putative molecular mechanism introduced the basic knowledge and current status of LA and put forward some of our research ideas and results from our molecular genetics research, which may pave the way for deciphering the putative pathogenic mechanism, risk factor, epigenetic index, and its application in diagnostic agents or drug target for prevention and treatment. Thus, it could provide clinicians and researchers with a specific and modern overview of LA to enable the understanding of recent progress and future directions in this illness.

Neurocognitive intra-individual variability in mood disorders: effects on attentional response time distributions

BACKGROUND

Attentional impairment is a core cognitive feature of major depressive disorder (MDD) and bipolar disorder (BD). However, little is known of the characteristics of response time (RT) distributions from attentional tasks. This is crucial to furthering our understanding of the profile and extent of cognitive intra-individual variability (IIV) in mood disorders.

METHOD

A computerized sustained attention task was administered to 138 healthy controls and 158 patients with a mood disorder: 86 euthymic BD, 33 depressed BD and 39 medication-free MDD patients. Measures of IIV, including individual standard deviation (iSD) and coefficient of variation (CoV), were derived for each participant. Ex-Gaussian (and Vincentile) analyses were used to characterize the RT distributions into three components: mu and sigma (mean and standard deviation of the Gaussian portion of the distribution) and tau (the 'slow tail' of the distribution).

RESULTS

Compared with healthy controls, iSD was increased significantly in all patient samples. Due to minimal changes in average RT, CoV was only increased significantly in BD depressed patients. Ex-Gaussian modelling indicated a significant increase in tau in euthymic BD [Cohen's d = 0.39, 95% confidence interval (CI) 0.09-0.69, p = 0.011], and both sigma (d = 0.57, 95% CI 0.07-1.05, p = 0.025) and tau (d = 1.14, 95% CI 0.60-1.64, p < 0.0001) in depressed BD. The mu parameter did not differ from controls.

CONCLUSIONS

Increased cognitive variability may be a core feature of mood disorders. This is the first demonstration of differences in attentional RT distribution parameters between MDD and BD, and BD depression and euthymia. These data highlight the utility of applying measures of IIV to characterize neurocognitive variability and the great potential for future application.

Optimization of a Clinically Relevant Model of White Matter Stroke in Mice: Histological and Functional Evidences

BACKGROUND AND PURPOSE

White matter (WM) injury during stroke increases the risk of disability and gloomy prognosis of post-stroke rehabilitation. However, modeling of WM loss in rodents has proven to be challenging.

METHODS

We report improved WM injury models in male C57BL/6 mice. Mice were given either endothelin-1 (ET-1) or L-N5-(1-iminoethyl)ornitine (L-NIO) into the periventricular white matter (PVWM), in the corpus callosum (CC), or in the posterior limb of internal capsule (PLIC). Anatomical and functional outcomes were quantified on day 7 post injection.

RESULTS

Injection of ET-1 or L-NIO caused a small focal lesion in the injection site in the PVWM. No significant motor function deficits were observed in the PVWM lesion model. We next targeted the PLIC by using single or double injections of L-NIO and found that this strategy induced small focal infarction. Interestingly, injection of L-NIO in the PLIC also resulted in gliosis, and significant motor function deficits.

CONCLUSIONS

By employing different agents, doses, and locations, this study shows the feasibility of inducing brain WM injury accompanied with functional deficits in mice. Selective targeting of the injury location, behavioral testing, and the agents chosen to induce WM injury are all keys to successfully develop a mouse model and subsequent testing of therapeutic interventions against WM injury.

Considerations for the Optimization of Induced White Matter Injury Preclinical Models

White matter (WM) injury in relation to acute neurologic conditions, especially stroke, has remained obscure until recently. Current advances in imaging technologies in the field of stroke have confirmed that WM injury plays an important role in the prognosis of stroke and suggest that WM protection is essential for functional recovery and post-stroke rehabilitation. However, due to the lack of a reproducible animal model of WM injury, the pathophysiology and mechanisms of this injury are not well studied. Moreover, producing selective WM injury in animals, especially in rodents, has proven to be challenging. Problems associated with inducing selective WM ischemic injury in the rodent derive from differences in the architecture of the brain, most particularly, the ratio of WM to gray matter in rodents compared to humans, the agents used to induce the injury, and the location of the injury. Aging, gender differences, and comorbidities further add to this complexity. This review provides a brief account of the techniques commonly used to induce general WM injury in animal models (stroke and non-stroke related) and highlights relevance, optimization issues, and translational potentials associated with this particular form of injury.

Genetics of microstructure of the corpus callosum in older adults

The current study sought to examine the relative influence of genetic and environmental factors on corpus callosum (CC) microstructure in a community sample of older adult twins. Analyses were undertaken in 284 healthy older twins (66% female; 79 MZ and 63 DZ pairs) from the Older Australian Twins Study. The average age of the sample was 69.82 (SD = 4.76) years. Brain imaging scans were collected and DTI measures were estimated for the whole CC as well as its five subregions. Parcellation of the CC was performed using Analyze. In addition, white matter lesion (WMLs) burden was estimated. Heritability and genetic correlation analyses were undertaken using the SOLAR software package. Age, sex, scanner, handedness and blood pressure were considered as covariates. Heritability (h²) analysis for the DTI metrics of whole CC, indicated significant h² for fractional anisotropy (FA) (h² = 0.56; p = 2.89×10⁻¹⁰), mean diffusivity (MD) (h² = 0.52; p = 0.30×10⁻⁶), radial diffusivity (RD) (h² = 0.49; p = 0.2×10⁻⁶) and axial diffusivity (AD) (h² = 0.37; p = 8.15×10⁻⁵). We also performed bivariate genetic correlation analyses between (i) whole CC DTI measures and (ii) whole CC DTI measures with total brain WML burden. Across the DTI measures for the whole CC, MD and RD shared 84% of the common genetic variance, followed by MD- AD (77%), FA - RD (52%), RD - AD (37%) and FA – MD (11%). For total WMLs, significant genetic correlations indicated that there was 19% shared common genetic variance with whole CC MD, followed by CC RD (17%), CC AD (16%) and CC FA (5%). Our findings suggest that the CC microstructure is under moderate genetic control. There was also evidence of shared genetic factors between the CC DTI measures. In contrast, there was less shared genetic variance between WMLs and the CC DTI metrics, suggesting fewer common genetic variants.

Renin-angiotensin system genetic polymorphisms and brain white matter lesions in older Australians

BACKGROUND

White matter lesions (WMLs), seen as hyperintensities on T2-weighted magnetic resonance imaging brain scans, are common in the brains of healthy older individuals. They are thought to be related to cerebral small vessel disease and to have a genetic component to their aetiology, and hypertension is thought to be an important risk factor. Genetic polymorphisms in hypertension-related genes may therefore be associated with the formation of WMLs.

METHODS

In this study, a sample of 445 Australians aged 60-65 years was drawn from a larger longitudinal epidemiological study, the Personality and Total Health Through Life Project. The associations of single nucleotide polymorphisms (SNPs) in the genes encoding angiotensinogen (AGT, rs699), angiotensin-converting enzyme (ACE, rs4362), and angiotensin II receptor type 1 (AGTR1, rs5182) with WMLs were examined.

RESULTS

No individual SNPs showed a significant association with WMLs for the whole sample. When the cohort was stratified by sex, ACE rs4362 and AGT rs699 showed significant associations with WMLs in men only (P = 0.01 and P = 0.03, respectively), and remained significant after controlling for hypertension. Although the AGTR1 SNP did not show any association with WMLs, the interaction of the AGT rs699 and AGTR1 rs5182 SNPs with WMLs was significant before (P = 0.03) and after adjustment for hypertension (P = 0.045).

CONCLUSIONS

The results provide evidence for association of polymorphisms in the renin-angiotensin system genes with WMLs, independent of hypertension. Male-only associations with WMLs were found for the AGT rs699 and ACE rs362 polymorphisms. Moreover, for the entire sample an interaction between AGT and AGTR1 rs5182 genotypes on WMLs was observed.

Impairments in Episodic-Autobiographical Memory and Emotional and Social Information Processing in CADASIL during Mid-Adulthood

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) - is the most common genetic source of vascular dementia in adults, being caused by a mutation in NOTCH3 gene. Spontaneous de novo mutations may occur, but their frequency is largely unknown. Ischemic strokes and cognitive impairments are the most frequent manifestations, but seizures affect up to 10% of the patients. Herein, we describe a 47-year-old male scholar with a genetically confirmed diagnosis of CADASIL (Arg133Cys mutation in the NOTCH3 gene) and a seemingly negative family history of CADASIL illness, who was investigated with a comprehensive neuropsychological testing battery and neuroimaging methods. The patient demonstrated on one hand severe and accelerated deteriorations in multiple cognitive domains such as concentration, long-term memory (including the episodic-autobiographical memory domain), problem solving, cognitive flexibility and planning, affect recognition, discrimination and matching, and social cognition (theory of mind). Some of these impairments were even captured by abbreviated instruments for investigating suspicion of dementia. On the other hand the patient still possessed high crystallized (verbal) intelligence and a capacity to put forth a façade of well-preserved intellectual functioning. Although no definite conclusions can be drawn from a single case study, our findings point to the presence of additional cognitive changes in CADASIL in middle adulthood, in particular to impairments in the episodic-autobiographical memory domain and social information processing (e.g., social cognition). Whether these identified impairments are related to the patient's specific phenotype or to an ascertainment bias (e.g., a paucity of studies investigating these cognitive functions) requires elucidation by larger scale research.

The single nucleotide polymorphism rs2208454 confers an increased risk for ischemic stroke: a case-control study

AIM

A recent genome-wide association study identified a strong association of covert magnetic resonance imaging infarcts with the single nucleotide polymorphism (SNP) rs2208454. The aim of this study was to determine whether the rs2208454 polymorphism is associated with an increased risk for ischemic stroke (IS).

METHODS

Ischemic stroke patients (n = 712) and control subjects (n = 774) from a southern Chinese Han population were included. The snapshot technique was used for genotype analysis.

RESULTS

Compared with the GT+GG or GG genotype, the frequency of the TT genotype was significantly higher in IS than in controls. After adjusting for age, gender, family history of IS, hypertension history, and history of diabetes mellitus, a significant correlation between the TT genotype and IS persisted (TT vs. GT+GG: adjusted OR = 1.79, 95% CI: 1.16-2.77; TT vs. GG: adjusted OR = 1.88, 95% CI: 1.20-2.94). In subgroup analyses, SNP rs2208454 was significantly associated with large artery atherosclerosis (LAA) (TT vs. GG: adjusted OR = 2.16, 95% CI: 1.19-3.93), but failed to show significant association with small-artery occlusion or cardioembolism IS subtypes.

CONCLUSIONS

Single nucleotide polymorphism rs2208454 confers an increased risk for IS in a southern Chinese Han population. When the IS subtype was examined, the effect of the SNP was restricted to LAA.

Associations of white matter integrity and cortical thickness in patients with schizophrenia and healthy controls

Typical brain development includes coordinated changes in both white matter (WM) integrity and cortical thickness (CT). These processes have been shown to be disrupted in schizophrenia, which is characterized by abnormalities in WM microstructure and by reduced CT. The aim of this study was to identify patterns of association between WM markers and cortex-wide CT in healthy controls (HCs) and patients with schizophrenia (SCZ). Using diffusion tensor imaging and structural magnetic resonance imaging data of the Mind Clinical Imaging Consortium study (130 HC and 111 SCZ), we tested for associations between (a) fractional anisotropy in selected manually labeled WM pathways (corpus callosum, anterior thalamic radiation, and superior longitudinal fasciculus) and CT, and (b) the number of lesion-like WM regions ("potholes") and CT. In HC, but not SCZ, we found highly significant negative associations between WM integrity and CT in several pathways, including frontal, temporal, and occipital brain regions. Conversely, in SCZ the number of WM potholes correlated with reduced CT in the left lateral temporal gyrus, left fusiform, and left lateral occipital brain area. Taken together, we found differential patterns of association between WM integrity and CT in HC and SCZ. Although the pattern in HC can be explained from a developmental perspective, the reduced gray matter CT in SCZ patients might be the result of focal but spatially heterogeneous disruptions of WM integrity.

Cognitive dysfunction and depression in Fabry disease: a systematic review

BACKGROUND

Fabry disease, an X-linked lysosomal storage disorder, leads to multi-organ dysfunction, including cerebrovascular disease and psychological disorders. However, the prevalence and pattern of associated cognitive dysfunction is not well understood.

OBJECTIVES

To investigate whether there is reliable evidence for neuropsychological impairment in patients with Fabry disease and which cognitive domains are affected. To estimate the prevalence of and factors associated with depression in patients with Fabry disease.

METHOD

Qualitative systematic review of the literature of studies conducting neuropsychological assessment or measuring the prevalence of depression in adults with Fabry disease using the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines where appropriate.

RESULTS

There is some evidence for neuropsychological impairment in Fabry disease in executive functioning, information processing speed and attention, with preservation of: general intellectual functioning, memory, naming, perceptual functioning and global cognitive functioning. Prevalence rates of depression in Fabry disease ranged from 15% to 62%, with the largest study to date reporting a prevalence rate of 46%. The most common factor associated with depression was neuropathic pain, both directly and indirectly by affecting social and adaptive functioning.

CONCLUSION

Our review suggests that Fabry disease may be associated with a characteristic pattern of cognitive deficits and a high prevalence of psychological disorders such as depression but highlights the limited available data. Exploring the nature of cognitive impairment in Fabry disease using standardised neuropsychological assessment, brain imaging and measures of depression is an important task for future research.

The contribution of twins to the study of cognitive ageing and dementia: the Older Australian Twins Study

The Older Australian Twins Study (OATS) is a major longitudinal study of twins, aged ≥ 65 years, to investigate genetic and environmental factors and their interactions in healthy brain ageing and neurocognitive disorders. The study collects psychiatric, neuropsychological, cardiovascular, metabolic, biochemical, neuroimaging, genomic and proteomic data, with two-yearly assessments, and is currently in its third wave. The initial cohort comprises 623 individuals (161 monozygotic and 124 dizygotic twin pairs; 1 MZ triplets; 27 single twins and 23 non-twin siblings), of whom 426 have had wave 2 assessment. A number of salient findings have emerged thus far which assist in the understanding of genetic contributions to cognitive functions such as processing speed, executive ability and episodic memory, and which support the brain reserve hypothesis. The heritability of brain structures, both cortical and subcortical, brain spectroscopic metabolites and markers of small vessel disease, such as lacunar infarction and white matter hyperintensities, have been examined and can inform future genetic investigations. Work on amyloid imaging and functional magnetic resonance imaging is proceeding and epigenetic studies are progressing. This internationally important study has the potential to inform research into cognitive ageing in the future, and offers an excellent resource for collaborative work.

Clinical neurogenetics: stroke

Understanding the genetic architecture of cerebrovascular disease holds promise of novel stroke prevention strategies and therapeutics that are both safe and effective. Apart from a few single-gene disorders associated with cerebral ischemia or intracerebral hemorrhage, stroke is a complex genetic phenotype that requires careful ascertainment and robust association testing for discovery and validation analyses. The recently uncovered shared genetic contribution between clinically manifest stroke syndromes and closely related intermediate cerebrovascular phenotypes offers effective and efficient approaches to complex trait analysis.

Multifocal white matter lesions associated with the D313Y mutation of the α-galactosidase A gene

White matter lesions (WML) are clinically relevant since they are associated with strokes, cognitive decline, depression, or epilepsy, but the underlying etiology in young adults without classical risk factors still remains elusive. Our aim was to elucidate the possible clinical diagnosis and mechanisms leading to WML in patients carrying the D313Y mutation in the α-galactosidase A (GLA) gene, a mutation that was formerly described as nonpathogenic. Pathogenic GLA mutations cause Fabry disease, a vascular endothelial glycosphingolipid storage disease typically presenting with a symptom complex of renal, cardiac, and cerebrovascular manifestations. We performed in-depths clinical, biochemical and genetic examinations as well as advanced magnetic resonance imaging analyses in a pedigree with the genetically determined GLA mutation D313Y. We detected exclusive neurologic manifestations of the central nervous system of the “pseudo”-deficient D313Y mutation leading to manifest WML in 7 affected adult family members. Furthermore, two family members that do not carry the mutation showed no WML. The D313Y mutation resulted in a normal GLA enzyme activity in leukocytes and severely decreased activities in plasma. In conclusion, our results provide evidence that GLA D313Y is potentially involved in neural damage with significant WML, demonstrating the necessity of evaluating patients carrying D313Y more thoroughly. D313Y might broaden the spectrum of hereditary small artery diseases of the brain, which preferably occur in young adults without classical risk factors. In view of the existing causal therapy regime, D313Y should be more specifically taken into account in these patients.

Associations between T1 white matter lesion volume and regional white matter microstructure in aging

White matter lesions, typically manifesting as regions of signal intensity abnormality (WMSA) on MRI, increase in frequency with age. However, the role of this damage in cognitive decline and disease is still not clear, as lesion volume has only loosely been associated with clinical status. Diffusion tensor imaging (DTI) has been used to examine the quantitative microstructural integrity of white matter, and has applications in the examination of subtle changes to tissue that appear visually normal on conventional imaging. The primary goal of this study was to determine whether major macrostructural white matter damage, (total WMSA volume), is associated with microstructural integrity of normal appearing white matter, and if these macrostructural changes fully account for microstructural changes. Imaging was performed in 126 nondemented individuals, ages 43-85 years, with no history of cerebrovascular disease. Controlling for age, greater WMSA volume was associated with decreased fractional anisotropy (FA) in widespread brain regions. Patterns were similar for FA and radial diffusivity but in contrast, WMSA was associated with axial diffusivity in fewer areas. Age was associated with FA in several regions, and many of these effects remained even when controlling for WMSA volume, suggesting the etiology of WMSAs does not fully account for all age-associated white matter deterioration. These results provide evidence that WMSA volume is associated with the integrity of normal-appearing white matter. In addition, our results suggest that overt lesions may not account for the association of increasing age with decreased white matter tissue integrity.

T2 hyperintensity of medial lemniscus: higher threshold application to ROI measurements is more accurate in predicting small vessel disease

BACKGROUND

Medial lemniscus T2 hyperintensity (MLH) has been recently demonstrated as potential imaging marker for small vessel disease (SVD). Our purpose in this study is to improve accuracy of regions of interest (ROI) analysis for this imaging finding.

METHODS AND METHODS

Two neuroradiologists retrospectively reviewed 103 consecutive outpatient brain MRI. Medial lemniscus signal in dorsal pons was evaluated; visually on FLAIR and with ROI on T2. Original MRI interpretations were divided into three categories; SVD, multiple sclerosis (MS), and nonspecific WM changes (non).

RESULTS

Thirty-seven patients had SVD, 14 patients had MS, 52 had Non. Visual MLH was seen exclusively with SVD and was generally bilateral. Patients with visual MLH belonged to advanced SVD by imaging and clinical parameters. Compared to visual data, ROI analyses of MLH has been known to be compounded by false positives and negatives at low threshold (20% of adjacent to normal brainstem signal). With application of higher ROI threshold (25%), false positives were eliminated but false negatives increased. ROI analyses of MLH by experienced neuroradiologist were more reliable.

CONCLUSION

MLH seen on high threshold ROI analysis is a reliable radiologic marker in predicting SVD. ROI analysis of MLH should be performed by an experienced neuroradiologist.

T2 hyperintensity of medial lemniscus is an indicator of small-vessel disease

OBJECTIVE

Small-vessel disease is a common MRI finding that can be difficult to differentiate from other white matter (WM) diseases because of the lack of a specific pattern of brain involvement. The purpose of our study was to evaluate medial lemniscus hyperintensity seen on FLAIR images as an imaging marker for small-vessel disease.

MATERIALS AND METHODS

Two blinded neuroradiologists retrospectively reviewed 103 consecutive outpatient brain MRI studies. Medial lemniscus signal in the dorsal pons was evaluated visually on FLAIR images and after placing regions of interest (ROIs) on T2-weighted images. On the basis of the original interpretations, scans were divided into three categories: small-vessel disease, multiple sclerosis (MS), and normal or nonspecific WM changes. Cardiovascular risk factors were recorded. Analysis of variance and Fisher exact tests were used to determine group differences, and kappa statistics was used to determine interrater agreement.

RESULTS

Thirty-seven patients had small-vessel disease, 14 patients had MS, and 52 had nonspecific WM changes. Medial lemniscus hyperintensity was seen in about 20% of patients with small-vessel disease and was generally bilateral. Although ROI analyses identified a slightly higher number of patients with medial lemniscus signal > 20% of adjacent to normal-appearing brainstem, interrater reliability was moderate, and there were false-positive and false-negative cases in comparison with visual data. When small-vessel disease patients were further subdivided into mild or advanced subgroups, medial lemniscus hyperintensity was selectively seen in advanced small-vessel disease. Patients with medial lemniscus hyperintensity were older (p < 0.001) and had higher prevalence of diabetes (p = 0.03), hypertension (p = 0.009), and hypercholesterolemia (p = 0.03).

CONCLUSION

Medial lemniscus hyperintensity seen on FLAIR images is a reliable radiologic marker of advanced small-vessel disease.

Heterozygote genotypes at rs2222823 and rs2811712 SNP loci are associated with cerebral small vessel disease in Han Chinese population

AIMS

With developments of etiology of cerebral small vessel disease (CSVD) and genome-wide association study (GWAS) of stroke, the genetic studies of CSVD are focused on genes related to blood-brain barrier (BBB) and aging. The project aims to investigate the association between CSVD and susceptibility loci and candidate genes.

METHODS

All study subjects admitted Beijing Tiantan Hospital from June 2009 to September 2010 including 197 cerebral small vessel disease patients(S), 198 large artery atherosclerosis control individuals (vascular stenotic rate ≥50% diameter reduction) (L), 200 hypertensive intracerebral hemorrhage control individuals (H) and 197 stroke-free control individuals (C). 15 SNPs in 4 genes (MYLK, AQP4, NINJ2, and INK4/ARF) were genotyped using Multiplex Snapshot assay. Each SNP was first examined between the groups S and C in different genetic models (codominant, dominant, recessive, overdominant, and log-additive). Permutation correction was used to adjust for multiple testing. The significant SNP loci were further analyzed in comparing S with L and H, respectively. Subgroup analysis was also performed for each risk-factor category.

RESULTS

Among the 15 SNPs, rs2222823 and rs2811712 were found to be significantly associated with CSVD after multiple-testing adjustment. The heterozygote (A/T) of rs2222823 of MYLK has an odds ratio of 0.52 (95% CI =[0.35, 0.79], P= 0.002, adjusted P= 0.031) when compared with homozygotes. The heterozygote (C/T) of rs2811712 of INK4/ARF has an odds ratio of 1.75 (95% CI =[1.13-2.71], P= 0.004, adjusted P= 0.050). The SNP rs2222823 was significant (P= 0.035) in comparing S with H. In comparing S versus L, it is significant for the subgroups of patients without diabetes (P= 0.012) and drinking (P= 0.018). rs2811712 was significant in comparing S with L for the subgroups of patients with hyperlipidemia (P= 0.029) and drinking (P= 0.04).

CONCLUSION

The heterozygotes (T/A) at the rs2222823 SNP locus of MYLK gene decreases the risk of having cerebral small vessel disease, while the heterozygotes (C/T) at the rs2811712 SNP locus of INK4/ARF gene increases the risk, suggesting that the MYLK and INK4/ARF are the associated genes of cerebral small vessel disease in Han Chinese population.