Effect of extracranial carotid artery stenosis and other risk factors for stroke on periventricular hyperintensity

Silent brain infarcts and white matter lesions in patients with asymptomatic carotid stenosis

The association of carotid atherosclerosis with silent brain infarcts (SBIs) and white matter lesions (WMLs) currently remains unknown. This study aims to compare SBIs, deep white matter lesions (DWMLs), and periventricular white matter lesions (PWMLs) in ipsilateral and contralateral hemispheres to internal carotid artery (ICA) stenosis, and investigate their association with stenosis grade in patients with asymptomatic ≥ 50% unilateral extracranial ICA stenosis. Patients without previous history of stroke and/or transient ischemic attack who had ≥ 50% stenosis in unilateral ICA on carotid color Doppler ultrasound were enrolled in the study. Patient demographics, vascular risk factors and ICA stenosis grades; number, location, and size of SBIs, DWMLs, and PWMLs in ICA territory were evaluated in both hemispheres using magnetic resonance imaging of the brain. Of the 69 patients, 53 had 50-69% (76.8%) and 16 had ≥ 70% (23.2%) unilateral ICA stenosis. There was no statistically significant difference in SBIs between ipsilateral and contralateral hemispheres to ≥ 50% ICA stenosis. Comparison of ICA stenoses as 50-69% and ≥ 70% revealed a greater number of patients with SBI in ipsilateral hemisphere to ≥ 70% stenosis compared to contralateral (p = 0.025). The number of SBIs was also higher in ipsilateral hemisphere to ≥ 70% stenosis compared to contralateral (p = 0.022). While DWMLs and PWMLs did not differ between hemispheres, frequency of Fazekas grade 1 DWMLs was lower in ipsilateral hemisphere to either 50-69% or ≥ 70% ICA stenosis compared to contralateral (p = 0.035 and p = 0.025, respectively). Results of the present study indicate that stenosis grade may be relevant in the association between asymptomatic carotid stenosis and SBIs, and ≥ 70% stenosis may pose a risk of SBI development.

Diabetic polyneuropathy, deep white matter lesions, and carotid atherosclerosis: is there any association?

The morphologic and functional damages of diabetes mellitus (DM) on microcirculation can play a role in the pathogenesis of both polyneuropathy and cerebral white matter lesions. The aim of this study is to investigate the relation between polyneuropathy and cerebral deep white matter lesions (DWMLs) and carotid atherosclerosis in patients with type 2 DM. Sixty-six patients with type 2 DM without any disorder that may cause polyneuropathy, and vascular risk factors except for DM and hyperlipidemia were included in the study. DWMLs and carotid atherosclerosis were investigated in patients with and without polyneuropathy. Forty patients (60.6%) had diabetic sensorimotor polyneuropathy. DWMLs were more frequent in patients with polyneuropathy compared to patients without polyneuropathy (p = 0.003). Logistic regression analysis confirmed association between polyneuropathy and DWMLs after adjusted for age (p = 0.013), duration of DM (p = 0.007), and both age and duration of DM (p = 0.016). No statistically significant difference was found between patients with and without polyneuropathy for carotid atherosclerosis. Among patients with polyneuropathy, those having DWMLs had higher mean age (p = 0.003) and longer symptom duration (p = 0.020) compared to patients without DWMLs. No association was found between DWMLs and carotid atherosclerosis. Polyneuropathy and cerebral DWMLs in type 2 DM patients may share common pathogenesis; presence and duration of polyneuropathy symptoms may predict ischemic white matter damage independent of carotid atherosclerosis.

Multiple Factors Involved in the Pathogenesis of White Matter Lesions

White matter lesions (WMLs), also known as leukoaraiosis (LA) or white matter hyperintensities (WMHs), are characterized mainly by hyperintensities on T2-weighted or fluid-attenuated inversion recovery (FLAIR) images. With the aging of the population and the development of imaging technology, the morbidity and diagnostic rates of WMLs are increasing annually. WMLs are not a benign process. They clinically manifest as cognitive decline and the subsequent development of dementia. Although WMLs are important, their pathogenesis is still unclear. This review elaborates on the advances in the understanding of the pathogenesis of WMLs, focusing on anatomy, cerebral blood flow autoregulation, venous collagenosis, blood brain barrier disruption, and genetic factors. In particular, the attribution of WMLs to chronic ischemia secondary to venous collagenosis and cerebral blood flow autoregulation disruption seems reasonable. With the development of gene technology, the effect of genetic factors on the pathogenesis of WMLs is gaining gradual attention.

The association between leukoaraiosis and carotid atherosclerosis: a systematic review and meta-analysis

The association between large-artery atherosclerosis and leukoaraiosis (LA) has been increasingly reported with inconsistent conclusion. This systematic review examines the relationship between LA and carotid atherosclerosis, manifested as atherosclerotic stenosis, plaques and increased intima-media thickness (IMT). PubMed, Embase, and Web of Science were searched for articles published up to February 2014. Thirty-two studies that examined the relationship between LA and carotid atherosclerosis were included. All statistical analysis was conducted with Review Manager 5.2.4. Finally, 32 studies including 17,721 patients were identified. There were 7 (30%) out of 23 studies reporting significant association between LA and carotid stenosis; 11 (79%) out of 14 studies reporting significant association between LA and carotid plaque; all 9 studies reporting significant association between LA and carotid IMT; one study showing an association between LA and CAWT (similar to the role of the IMT). The quantitative meta-analysis of 10 studies showed that carotid atherosclerosis was not associated with LA (OR: 1.10; 95% CI: 0.61-1.98). A significant association was found between LA and carotid plaque (OR = 3.53; 95% CI = 1.83-6.79), and the result of IMT group showed that IMT increased risk of LA (MD = 0.11; 95% CI = 0.01-0.22). This systematic review suggested that LA has a tendency of association with carotid plaques but no association with simple carotid stenosis.

Lack of association of white matter lesions with ipsilateral carotid artery stenosis

Background

White matter lesions (WML) are commonly seen on brain MRI and are generally considered a marker of tissue damage from cerebral small vessel disease. WML are associated with increasing age and vascular risk factors, but their precise cause is unknown. A role for carotid artery atherothromboemboli has been suggested. If this is the case, more WML would be expected ipsilateral to increasing degrees of carotid stenosis.

Methods

We recruited patients with ischaemic stroke from two large, separate prospective stroke studies, assessed with brain MRI and carotid Doppler ultrasound. We scored hemispheric WML visually in periventricular and deep locations. We assessed the association between carotid stenosis asymmetry and WML asymmetry, and vice versa. Further, we assessed the association between carotid stenosis and ipsilateral WML, before and after adjusting for vascular risk factors, and tested associations between ipsilateral and contralateral stenoses and WML.

Results

We recruited 247 (Study 1) and 253 (Study 2) patients. In Study 1 and Study 2, 36 (15%) and 29 (11%) patients had ≥50% carotid stenosis, and 27 (11%) and 15 (6%) had ≥70% stenosis, respectively. Carotid stenosis was asymmetric in 28 (11%) and 26 (10%) patients and WML were asymmetric in 22 (9%) and 11 (4%) patients in Study 1 and Study 2, respectively. We found no association between carotid stenosis and ipsilateral WML score, before or after adjusting for vascular risk factors or sidedness, but WML were strongly associated with increasing age (p < 0.001).

Conclusion

In two large cohorts of ischaemic stroke patients, we found no association between carotid stenosis and ipsi- or contralateral WML. There is now substantial evidence that atherothromboemboli are unlikely to cause most WML or other forms of cerebral small vessel lesions. Future studies should focus on determining what causes the intrinsic small vessel pathological changes that appear to underlie most WML.

MRI is a sensitive marker of subtle white matter pathology in hypoperfused mice

White matter (WM) abnormalities, possibly resulting from hypoperfusion, are key features of the aging human brain. It is unclear, however, whether in vivo magnetic resonance imaging (MRI) approaches, such as diffusion tensor and magnetization transfer MRI are sufficiently sensitive to detect subtle alterations to WM integrity in mouse models developed to study the aging brain. We therefore investigated the use of diffusion tensor and magnetization transfer MRI to measure structural changes in 4 WM tracts following 1 month of moderate hypoperfusion, which results in diffuse WM pathology in C57Bl/6J mice. Following MRI, brains were processed for evaluation of white and gray matter pathology. Significant reductions in fractional anisotropy were observed in the corpus callosum (p = 0.001) and internal capsule (p = 0.016), and significant decreases in magnetization transfer ratio were observed in the corpus callosum (p = 0.023), fimbria (p = 0.032), internal capsule (p = 0.046) and optic tract (p = 0.047) following hypoperfusion. Hypoperfused mice demonstrated diffuse axonal and myelin pathology which was essentially absent in control mice. Both fractional anisotropy and magnetization transfer ratio correlate with markers of myelin integrity/degradation and not axonal pathology. The study demonstrates that in vivo MRI is a sensitive measure of diffuse, subtle WM changes in the murine brain.

Correlation between ventricular enlargement and white matter changes

The clinical significance of white matter changes including periventricular hyperintensity (PVH) and deep white matter hyperintensity (DWMH) on MRI in patients with normal pressure hydrocephalus is unclear. We investigated the correlation between ventricular size and white matter changes in healthy individuals. We performed MRI in 683 (mean age 59; 55% men) neurologically normal adults without a history or radiological findings of brain disease or trauma, who were undergoing brain health screening. The correlation between Evans' index and severity of white matter changes was analyzed. Multiple linear regression analysis was used to identify the main clinical factors influencing ventricular enlargement and white matter changes. Evans' index was 0.248+/-0.026 (mean+/-SD). Incidence of PVH was 40% and DWMH was 29%. Evans' index was weakly correlated with PVH grading (rho=0.24; P<.01) and DWMH grading (rho=0.24; P<.01). Multiple linear regression analysis showed that age (beta=0.034; SE=0.003) diastolic blood pressure (0.004; 0.002), Evans' index (0.019; 0.009), and a history of hypertension (0.173; 0.053) had a significant impact on PVH grade, whereas age (0.030; 0.003) and history of hypertension (0.224; 0.049) were related to DWMH grade. It was suggested that there is an independent correlation between ventricular enlargement and PVH in normal adults. This finding in a normal population could be due to the presence of preclinical disease, but its bearing on the changes that occur in normal pressure hydrocephalus remain uncertain at the present time.

Intracranial carotid artery calcification on head CT and its association with ischemic changes on brain MRI in patients presenting with stroke-like symptoms: retrospective analysis

INTRODUCTION

Our purpose was to study the association between the intracranial arterial calcifications observed on head CT and brain infarcts demonstrated by MRI in patients presenting with acute stroke symptoms.

METHODS

Institutional review board approval was obtained for this retrospective study which included 65 consecutive patients presenting acutely who had both head CT and MRI. Arterial calcifications of the vertebrobasilar system and the intracranial cavernous carotid arteries (intracranial carotid artery calcification, ICAC) were assigned a number (1 to 4) in the bone window images from CT scans. These four groups were then combined into high calcium (grades 3 and 4) and low calcium (grades 1 and 2) subgroups. Brain MRI was independently evaluated to identify acute and chronic large-vessel infarcts (LVI) and small-vessel infarcts (SVI). The relationship between ICAC and infarcts was evaluated before and after adjusting for demographics and cardiovascular risk factors.

RESULTS

Statistical analysis could not be performed for the vertebrobasilar system due to an insufficient number of patients in the high calcium group. Of the 65 patients, 46 (71%) had a high ICAC grade on head CT. They were older and had a higher prevalence of cardiovascular risk factors. Acute SVI (P = 0.006), chronic SVI (P = 0.006) and acute LVI (P = 0.04) were associated with a high ICAC grade. After adjustment for age and other risk factors, only acute SVI was associated with a high ICAC grade (P = 0.002).

CONCLUSION

Although age emerged as the most important determinant of ischemic cerebral changes, there were rather complex interactions among multiple risk factors with different infarct types. A high ICAC grade demonstrated a correlation with acute SVI in our patients independent of these risk factors.

Advances in magnetic resonance imaging methods for the evaluation of bipolar disorder

This article reviews the current state of magnetic resonance imaging techniques as applied to bipolar disorder. Addressed are conventional methods of structural neuroimaging and recently developed techniques. This latter group comprises volumetric analysis, voxel-based morphometry, the assessment of T2 white matter hyperintensities, shape analysis, cortical surface-based analysis, and diffusion tensor imaging. Structural analysis methods used in magnetic resonance imaging develop exponentially, and now present opportunities to identify disease-specific neuroanatomic alterations. Greater acuity and complementarity in measuring these alterations has led to the generation of further hypotheses regarding the pathophysiology of bipolar disorder. Included in the summary of findings is consideration of a resulting neuroanatomic model. Integrative issues and future directions in this relatively young field, including multi-modal approaches enabling us to produce more comprehensive results, are discussed.

Neuroimaging in drug and substance abuse part II: opioids and solvents

The central nervous system is one of the primary targets for the detrimental effects of drugs of abuse. Diagnostic imaging, especially MRI, plays an important role in the detection of complications associated with drug abuse. We present the imaging findings associated with the abuse of opioids and other morphine derivatives, as well, as solvents. Of the morphine derivatives, heroin is the most commonly abused. Several CNS pathologic effects have been described in association with its abuse. These include neurovascular complications such as microvascular ischemic changes or ischemic stroke. A rare form of leukoencephalopathy has been described in those abusers who inhale heroin vapors. Other neurologic complications include atrophy and various infectious processes. Solvent inhalation is a common practice among adolescents and young adults secondary to its ease of access and low cost. The most important component of industrial solvents is toluene. Complications of toluene abuse may be either acute, showing no neuroradiological changes, or chronic, characterized by cerebral and cerebellar demyelination as well as atrophy.

Relationship of deep white matter hyperintensities and cerebral blood flow in severe carotid artery stenosis

Leukoaraiosis (LA) has been associated with abnormalities of both large and small blood vessels. This study attempts to clarify the pathogenesis of LA by testing the hypothesis that increased frequency of LA with occlusive extra-cranial arterial disease results directly from global reduction in cerebral blood flow (CBF). Thirty-five normal subjects and 55 patients with carotid stenosis (>70%) were studied using MR. CBF was measured using phase contrast MR angiography and LA was scored using previously validated scoring system. Patients were divided into those with evidence of previous infarction on MRI and those without. LA was more severe in patients than in normal subjects (P<0.01) and correlated with age in normal subjects but not in patients. CBF in patients with (809+/-214 ml/min) and without infarction (mean 792+/-181 ml/min) was significantly lower than in normal subjects (mean 1073+/-194 ml/min). There was no correlation between the severity of LA and measured CBF in any group. The severity of LA is greater in patients with severe carotid stenosis but is not correlated to reductions in CBF. This suggests that microvascular abnormality is the dominant pathogenetic factor in LA even in the presence of severe stenotic/occlusive large vessel disease.

White matter lesions in watershed territories studied with MRI and parenchymography: a comparative study

Brain aging affects an increasing segment of the population and the role of chronic cerebrovascular disease is considered to be one of the main parameters involved. For this purpose we compared retrospectively MRI data with digitized subtraction angiography (DSA) data in a group of 50 patients focusing onto the watershed area of the carotid artery vascular territories. In order to evaluate the presence of white matter lesions (WML) in the hemispheric watershed areas, coronal fluid-attenuated inversion-recovery or axial T2 weighted MRI images of patients with symptomatic cerebrovascular insufficiency areas were compared with the capillary phase of DSA studies in anterior-posterior projection. Presence of cerebrovascular occlusive disease was evaluated on DSA using North American symptomatic carotid endarterectomy trial criteria and including evaluation of collateral vascular supply. Pathological MRI findings in the region of the watershed territories correlated overall in 66% of cases with a defect or delayed filling on DSA. In the case of asymmetrical MRI findings, there was a pathological finding of the capillary phase in the watershed area in 92% of DSA studies. Hypoperfusion in the capillary phase of the watershed area as seen on DSA correlated with the stenosis degree of the concerned carotid artery. Our findings suggest that asymmetrical findings of WML in the watershed areas as seen on MRI are caused by hemodynamic effect and a differentiation between small vessel disease and a consequence of distant stenosis may be possible under such conditions.

Evaluation of extracranial carotid artery duplex ultrasound scanning parameters in cerebral ischemic or nonischemic patients without significant cervical carotid artery stenosis

Although extracranial carotid artery duplex ultrasound scanning (ECADUS) is frequently used to detect cervical carotid artery stenosis, the method for interpreting the parameters obtained by ECADUS is not well established when cervical carotid artery stenosis does not exist. We retrospectively studied the parameters obtained from 180 patients without significant cervical carotid artery stenosis. The peak systolic velocity (PSV), end diastolic velocity (EDV), pulsatility index (PI) and diameter of the cervical internal carotid artery, and intima media thickness (IMT) of the common carotid artery were obtained bilaterally. These parameters were evaluated according to the side and the patient's sex, age, and cerebral ischemic symptoms. No significant effects of the side or sex were observed on any parameters. Aging affected the IMT and PI positively and the EDV negatively. The PI correlated positively with the IMT. In the symptomatic group the PSV and EDV decreased; this was still observed after adjustments for age. These results confirm the effects of aging. PI seems to be another indicator of cerebral atherosclerosis, because it correlates well with IMT, a well-recognized indicator. Cerebral ischemic symptoms may be affected by reduced velocity more than by atherosclerotic progression. This phenomenon requires further evaluation.

White matter hyperintensities in subjects with cocaine and opiate dependence and healthy comparison subjects

The prevalence, severity, and location of white matter signal hyperintensities (WMH) on brain magnetic resonance images were compared in patients with cocaine or opiate dependence and healthy subjects. Patients with cocaine (n=32) and opiate dependence (n=32), whose diagnoses were confirmed with the Structured Clinical Interview for DSM-IV, and age- and sex-matched healthy subjects (n=32) were scanned using a 1.5 T whole body GE magnetic resonance scanner. Axial proton-density and T2-weighted images were obtained as well as fluid-attenuated inversion recovery axial images. The severity of WMH was assessed separately for deep (and insular) and periventricular WMH, using a modified composite version of the rating scales of Fazekas and Coffey. The cocaine-dependent group had greater severity of WMH than the opiate-dependent group, which in turn had greater severity of WMH than the healthy comparison group (odds ratios=2.54 and 2.90, respectively). The cocaine-dependent group had greater lesion severity of deep and insular WMH than the opiate-dependent group and the healthy comparison group (odds ratio>3.25 for deep WMH; odds ratio>4.38 for insular WMH). For periventricular WMH, there were no significant differences between the three groups. The frontal lobes were the predominant locations of WMH in both substance-dependent groups. The greater prevalence and severity of WMH in cocaine-dependent subjects than in opiate-dependent subjects may reflect the fact that cocaine induces more ischemia via vasoconstriction than opiates. Also, there was a trend for lower WMH severity in substance-dependent women relative to the healthy comparison group, possibly due to estrogen's protective effect against cerebrovascular accidents.

Characterization of cerebral microangiopathy using 3 Tesla MRI: correlation with neurological impairment and vascular risk factors

PURPOSE

To investigate whether clinical and neuropsychological impairment in cerebral small-vessel disease (CSVD) can be evaluated by means of morphological magnetic resonance imaging (MRI).

MATERIALS AND METHODS

MRI at 3 Tesla in T2- and T1-weighted sequences was evaluated in 44 patients with cerebral microangiopathy, and 30 patients with combined cerebral micro- and macroangiopathy. The MR characteristics were correlated to clinical data, attentional impairment, and the patients' individual vascular risk factor profiles. Fifteen healthy age-matched control subjects participated in the study to assess MR signal changes in nonhypertensive elderly subjects.

RESULTS

Patients and normal controls differed significantly in the extent of MR signal changes. A close relation between age, obesity, hypertension, and MR signal abnormalities was evident in all patients. Patients with pure CSVD additionally showed an association between their MR-defined severity of disease and their degree of neurological impairment, and their vascular risk score. In contrast, attentional impairment did not relate to the MR-defined severity of CSVD.

CONCLUSION

MR signal changes in CSVD show a close relationship to some risk factors of individual patients.

Associations of plasma endothelin concentration with carotid atherosclerosis and asymptomatic cerebrovascular lesions in patients with essential hypertension

We studied the association of endothelin (ET)-1 with carotid atherosclerosis and asymptomatic cerebrovascular lesions in patients with essential hypertension. Neurologically normal patients with essential hypertension (n=293; 138 male, 155 female; mean age, 65 years) and age-matched control subjects (n=242) were studied with B-mode ultrasonography of the common and internal carotid arteries and magnetic resonance imaging of the brain. Plasma ET-1 was measured by enzyme immunoassay. Hypertensive patients were divided into groups with carotid plaques and low ET-1 concentrations (< 0.75 pg/ml; PL group); carotid plaques and mid-range ET-1 (0.75 to 1.55 pg/ml; PM group); carotid plaques and high ET-1 (> or = 1.55 pg/ml; PH group); no plaques and low ET-1 (NPL); no plaques and mid-range ET-1 (NPM); and no plaques and high ET-1 (NPH). Overall, ET-1 concentrations were significantly higher in patients than in control subjects. Carotid plaque prevalence was significantly related to ET-1 in hypertensive patients. ET-1 showed a significant positive relationship with the number of asymptomatic lacunar infarcts of the brain in hypertensive patients with carotid plaques (rho=0.48, p<0.001). No significant relationship was seen between ET-1 and periventricular hyperintensity scores in patients with plaques. ET-1 did not show a relationship to either brain lesion type in patients without carotid plaques. Thus, ET-1 may foster asymptomatic lacunar cerebral infarcts by promoting carotid atherosclerosis in patients with essential hypertension.