Selective neuronal damage and chronic hemodynamic cerebral ischemia

Severity of Intracranial Large Artery Disease Correlates With Cerebral Small Vessel Disease

BACKGROUND

Small vessel disease (SVD) shares common vascular risk factors with large artery disease (LAD). However, little is known about the relationship between intracranial artery stenosis and SVD burden.

PURPOSE

To investigate whether SVD burden correlates with severity of intracranial LAD.

STUDY TYPE

Retrospective.

POPULATION

Five hundred and sixteen patients with LAD of arterial circulation were enrolled from one hospital, including 384 males (59 ± 11 years) and 132 females (60 ± 12 years).

FIELD STRENGTH/SEQUENCE

3 T. T₁ -weighted fast spin echo (T₁ W FSE), T₂ W FSE, T₂ fluid attenuated inversion recovery, diffusion-weighted imaging, susceptibility-weight imaging, and time-of-flight magnetic resonance angiography.

ASSESSMENT

The LAD was divided into mild stenosis (<30%), moderate stenosis (30%-69%), and severe stenosis (≥70%). The Standard for Reporting Vascular Changes on Neuroimaging criteria was used to rate the SVD burden according to the level of white matter hyperintensity (WMH), perivascular space (PVS), cerebral microbleed (CMB), and lacunes.

STATISTICAL TESTS

Lilliefors test, ANOVA, chi-squared test, Mann-Whitney U test, Wilcoxon signed rank test, Bonferroni test, Spearman's correlation, logistic regression, and Cohen's kappa test.

RESULTS

The grade scores for centrum semiovale PVS (CS-PVS) were positively correlated with the degree of stenosis (R = 0.413), whereas the presence of severe basal ganglia PVS (BG-PVS) was associated with CMB (R = 0.508), lacunes (R = 0.365), and severe WMH (R = 0.478). In multivariate analysis, severe CS-PVS (adjusted odds ratio [aOR], 3.1; 95% confidence interval [CI], 1.9-4.8) and lacunes (aOR, 2.1; 95% CI, 1.3-3.4) were associated with severe stenosis of LAD. In addition, CS-PVS was related to severe stenosis in a dose-dependent manner: when CS-PVS score was 3 and 4, the aORs of severe stenosis were 1.9 and 7.7, respectively.

DATA CONCLUSION

The severity of LAD in anterior circulation is associated with SVD burden, which suggests that different SVD burden may be used for risk stratification in LAD.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 3.

Effect of different parietal hypoperfusion on neuropsychological characteristics in mild cognitive impairment

BACKGROUND

In early-stage amnestic mild cognitive impairment (aMCI), differences in the neuropsychological characteristics of each individual are subtle. We investigated differences in neuropsychological performance between aMCI patients with and without hypoperfusion in the medial parietal regions (MP). We further compared patients with hypoperfusion in the left and right lateral parietal regions.

METHODS

We examined 165 aMCI patients (mean age: 76.8 ± 5.5 years; 87 women) who had undergone neuropsychological measurement and single-photon emission computed tomography. We classified participants into two subgroups with and without hypoperfusion: MP hypoperfusion (+) and MP hypoperfusion (-); classification was based on Z-scores (calculated by three-dimensional stereotactic surface projection technique) of three regions of interest in the parietal lobes (i.e. MP regions including posterior cingulate cortex and precuneus and left and right inferior parietal lobules (lateral parietal regions)). The MP hypoperfusion (-) group was classified into left lateral parietal hypoperfusion (+) and right lateral parietal hypoperfusion (+) subgroups. We performed either univariate or multivariate ancova to compare neuropsychological scores for continuous variables between groups and examined dichotomous variables using χ² tests.

RESULTS

In the overall aMCI sample, scores on logical memory delayed recall in the MP hypoperfusion (+) group were significantly lower than those in the MP hypoperfusion (-) group. Total scores on Rey-Osterrieth Complex Figure Test delayed recall were also marginally lower in the MP hypoperfusion (+) group than in the MP hypoperfusion (-) group. Comparisons of neuropsychological test scores between the left and right lateral parietal hypoperfusion (+) groups revealed no significant differences.

CONCLUSIONS

The present findings suggest that MP hypoperfusion (+) is associated with more robust memory deficits than MP hypoperfusion (-). Combining neuropsychological tests and single-photon emission computed tomography findings may be useful for early detection of cognitive decline in aMCI.

The Significance of Vascular Pathogenesis in the Examination of Corticobasal Syndrome

Corticobasal syndrome (CBS) is a clinical entity, classified as an atypical Parkinsonism, characterized by both motor and higher cortical dysfunctions. The clinical manifestation of CBS is associated with several pathologies, among which corticobasal degeneration (CBD) is the most common. The aim of our study was to elaborate on the possible vascular pathogenesis of CBS and consider types of vascular lesions in these cases. Several cases of vascular CBS are described in the literature. The majority of presented patients were affected by internal carotid artery (ICA) stenosis and ischemic strokes; few cases were associated with vascular malformations or autoimmune diseases. Vascular CBS is preceded by an abrupt onset. The clinical manifestation does not significantly differ with non-vascular CBS. Patients with vascular CBS are usually elderly; often with coexistent hypertension, dyslipidemia and diabetes mellitus. Inferring from our observations, cerebral hypoperfusion can play a significant role in neuropathological changes in neurodegenerative diseases. To the best of our knowledge paper is the first comprehensive review of vascular CBS and we are positive that our observations show that further research concerning the vascular pathogenesis of tauopathy atypical Parkinsonism is required.

Surgical therapy for chronic internal carotid artery occlusion: a systematic review and meta-analysis

Chronic internal carotid artery occlusion (CICAO) significantly increases the risk of recurrent stroke. Given unfavorable outcomes, revascularization procedures are not generally recommended for CICAO. In the last several years, loads of studies reported successful surgical revascularization for CICAO with promising success rate and favorable short-term outcomes. Meanwhile, due to the lack of high-quality evidence, the safety and efficacy of revascularization procedures remain debatable. This systematic review aims to scrutinize current evidence for the applicability of revascularization for CICAO. We also investigated potential predictors of postoperative prognosis. We searched clinical studies on surgical treatment of CICAO on the Medline, Cochrane library, and Embase databases, published from Jan 1990 to Jan 2021. Surgical operation was restricted to bypass surgery, endarterectomy, endovascular therapy, and hybrid surgery. Controlled clinical studies were included for clinical outcomes. Large-sample single-arm studies were supplemented to assess complications and success rate. Co-primary endpoints were technical success rate and neurological function; secondary endpoints were recurrent stroke/cerebrovascular events, complications, and deaths within follow-up. This systematic review has been registered in PROSPERO (CRD42020181250). One RCT and 5 cohort studies with a total of 465 patients were included in this review. Seven single-arm studies were supplemented for assessing success rate and complications. Bypass surgery presented the highest graft patency of 96% and a low incidence of complications, but no benefits on neurological function, recurrent stroke, or deaths. Endovascular therapy (carotid stenting) was characterized by a relatively lower technical success rate, significant neurological function recovery, and nonsignificant reduction of cerebrovascular events and deaths. Hybrid surgery was considered as a potential treatment for CICAO because of a high technical success rate and significant neurological improvement. Endarterectomy is only suitable for short-segment occlusion. Prospective clinical trials should focus on carotid stenting and hybrid surgery for their significant capacity of improving neurologic function and potential capacity of reducing deaths and cerebrovascular events.

Effects of site, cerebral perfusion and degree of cerebral artery stenosis on cognitive function

OBJECTIVE

To investigate the effects of site, cerebral perfusion and degree of cerebral artery stenosis (CAS) on cognitive function.

METHODS

A total of 57 patients with CAS and 53 controls from January 2019 to December 2019 were included. The former group was further divided into different subgroups according to the site, cerebral perfusion and degree of CAS. A series of neuropsychological tests were performed to evaluate the cognitive domains (such as memory, executive function, psychomotor speed, etc.). Rank sum test, t test, Chi-square test and analysis of variance were used for data analysis. Spearman correlation analysis was used to examine the relationship between the site, cerebral perfusion and degree of CAS and all tests' scores.

RESULTS

For patients with CAS who have decreased cerebral perfusion, their global cognitive function, memory, psychomotor speed, executive function and frontal lobe function were significantly impaired (all P < 0.05). There was a significant decrease in global cognitive function, psychomotor speed, memory, executive function and frontal lobe function in patients with anterior circulation stenosis (all P < 0.05). Moderate and severe CAS impaired subjects' global cognitive function, memory, psychomotor speed, executive function and frontal lobe function (all P < 0.05). There was a correlation between the site, cerebral perfusion, the degree of CAS and cognitive function.

CONCLUSION

Global cognitive function, memory, psychomotor speed, frontal lobe function and executive function are impaired in patients with CAS, especially in those with anterior circulatory stenosis, moderate to severe stenosis and low cerebral perfusion.See Video Abstract, http://links.lww.com/WNR/A613.

The stronger one-sided relative hypoperfusion, the more pronounced ipsilateral spatial attentional bias in patients with asymptomatic carotid stenosis

Patients with asymptomatic, high-grade internal carotid artery stenosis often suffer from subtle cognitive impairments with unclear underlying neuro-cognitive mechanisms. Thus, we hypothesized that stenosis-related unilateral cerebral hypoperfusion leads to an ipsilateral attentional bias; 22 patients with asymptomatic, one-sided high-grade carotid stenosis and 24 age-matched healthy controls underwent pseudo-continuous arterial spin labeling to assess brain perfusion in the territory of the carotid arteries. Furthermore, a parametric assessment of attention functions was carried out on the basis of the computational Theory of Visual Attention. Both patients' perfusion and spatial attention were significantly more lateralized than those of healthy controls. Critically, both asymmetry indices were significantly correlated in patients, i.e. the stronger one-sided relative hypoperfusion, the stronger ipsilateral bias of attention. This association was specifically pronounced in parietal cortices and independent of white matter hyperintensities as a surrogate for cerebrovascular brain damage. Results provide evidence for a link between lateralized hypoperfusion and lateralized attentional weighting in asymptomatic, high-grade carotid stenosis. Data suggest that lateralized hypoperfusion with simultaneous spatial attentional bias might serve as a potential therapeutic target in one-sided carotid stenosis.

Selective neuronal damage and blood pressure in atherosclerotic major cerebral artery disease

OBJECTIVE

In patients with atherosclerotic major cerebral artery disease, low blood pressure might impair cerebral perfusion, thereby exacerbate the risk of selective neuronal damage. The purpose of this retrospective study was to determine whether low blood pressure at follow-up is associated with increased selective neuronal damage.

METHODS

We retrospectively analysed data from 76 medically treated patients with atherosclerotic internal carotid artery or middle cerebral artery disease with no ischaemic episodes on a follow-up of 6 months or more. All patients had measurements of the distribution of central benzodiazepine receptors twice using positron emission tomography and ¹¹C-flumazenil. Using three-dimensional stereotactic surface projections, we quantified abnormal decreases in the benzodiazepine receptors of the cerebral cortex within the middle cerebral artery distribution and correlated these changes in the benzodiazepine receptors index with blood pressure values at follow-up examinations.

RESULTS

The changes in the benzodiazepine receptor index during follow-up (mean 27±21 months) were negatively correlated with systolic blood pressure at follow-up. The relationship between changes in benzodiazepine receptor index and systolic blood pressure was different among patients with and without decreased cerebral blood flow at baseline (interaction, p<0.005). Larger increases in benzodiazepine receptor index (neuronal damage) were observed at lower systolic blood pressure levels in patients with decreased cerebral blood flow than in patients without such decreases.

CONCLUSION

In patients without ischaemic stroke episodes at follow-up but with decreased cerebral blood flow due to arterial disease, low systolic blood pressure at follow-up may be associated with increased selective neuronal damage.

Acquired Hemicerebral Atrophy Secondary to Chronic Internal Carotid Steno-Occlusive Disease: A Case Series

Cerebral atrophy is a common finding in elderly patients; however, cerebrovascular disease causing progressive focal cerebral atrophy and dysfunction is unusual. In this report, we present 3 cases of hemicerebral atrophy due to ipsilateral internal carotid artery (ICA) stenosis or occlusion mimicking neurodegenerative conditions. Patient 1 had a frontal dysexecutive syndrome potentially consistent with a diagnosis of behavioral variant frontotemporal dementia; however, neuroimaging revealed a chronically occluded left ICA and a pattern of atrophy restricted to the left middle cerebral artery territory, suggestive of a vascular etiology. Patient 2 presented with progressively worsening seizures and right-sided weakness consistent with left hemispheric dysfunction, with radiographic evidence of left hemicerebral atrophy. Angiography revealed a chronic dissection of the left ICA leading to left cerebral hypoperfusion. Patient 3 had asymmetric parkinsonism, alien limb, and cognitive impairment consistent with a diagnosis of corticobasal syndrome. His imaging, however, revealed atrophy and encephalomalacia within the anterior circulation watershed territories with chronic, severe stenosis of the left ICA suggestive of a chronic hypoperfused state. In this case series, we report 3 examples of hemicerebral atrophy secondary to chronic ipsilateral ICA vascular disease with diverse progressive clinical symptoms mimicking primary neurodegenerative conditions. This case series highlights the importance of considering chronic hypoperfusion and large-vessel severe stenosis or occlusion in patients with cognitive impairment and evidence of asymmetric brain atrophy. In addition to symptomatic treatment, the management of vascular risk factors including treatment with antiplatelet agents, statins, and revascularization procedures can be considered.

Misery perfusion and amyloid deposition in atherosclerotic major cerebral artery disease

Although experimental studies have shown that global cerebral hypoperfusion leads to amyloid deposition in the hemisphere with carotid artery occlusion in rodents, the results of such occurrence are controversial in humans. Hence, we aim to determine whether global cerebral hypoperfusion leading to decreased blood flow relative to metabolic demand [increased oxygen extraction fraction (OEF), misery perfusion] is associated with increases in amyloid deposition in the hemisphere with atherosclerotic major cerebral artery disease in patients. We evaluated the distribution of β-amyloid plaques using positron emission tomography and a [18F]-pyridylbenzofuran derivative (¹⁸F-FPYBF-2) in 13 patients with unilateral atherosclerotic disease of the internal carotid artery (ICA) or middle cerebral artery (MCA) disease and no cortical infarction. The distribution volume ratio (DVR) of ¹⁸F- FPYBF-2 was calculated using dynamic data and Logan graphical analysis with reference tissue and was correlated with the cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO₂), and OEF, obtained from ¹⁵O-gas PET. The mean cortical value was calculated as the mean value within the frontal, posterior cingulate, precuneus, parietal, and lateral temporal cortical regions. Significant reductions in CBF and CMRO₂ and increases in OEF were found in the hemisphere ipsilateral to the arterial lesion compared with the contralateral hemisphere. There was no significant difference for ¹⁸F-FPYBF-2 DVR between hemispheres. The ipsilateral to contralateral ratio of the ¹⁸F- FPYBF-2 DVR was increased in 3 patients, while the ipsilateral to contralateral OEF ratio was increased in 4 patients. The incidence of an increased hemispheric DVR ratio was significantly higher in patients with an increased hemispheric OEF ratio (3/4) than in patients without (0/9) (p < 0.02). Although the ¹⁸F- FPYBF-2 DVR in the ipsilateral hemisphere was positively correlated with OEF after adjustment for the ¹⁸F- FPYBF-2 DVR in the contralateral hemisphere using multiple regression analysis (p < 0.05), the contribution rate of OEF was small (R² = 5.5%). Only one of the 4 patients with an increased hemispheric OEF ratio showed amyloid positivity based on the DVR value. In atherosclerotic major cerebral artery disease, misery perfusion accompanied only small increases of amyloid deposition at best. Misery perfusion was not associated with amyloid positivity.

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Misery perfusion accompanied only small increases of amyloid deposition at best.

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Relative oxygen extraction fraction correlated with relative amyloid deposition.

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Misery perfusion was not associated with amyloid positivity.

Altered cerebral hemodyamics and cortical thinning in asymptomatic carotid artery stenosis

Cortical thinning is a potentially important biomarker, but the pathophysiology in cerebrovascular disease is unknown. We investigated the association between regional cortical blood flow and regional cortical thickness in patients with asymptomatic unilateral high-grade internal carotid artery disease without stroke. Twenty-nine patients underwent high resolution anatomical and single-delay, pseudocontinuous arterial spin labeling magnetic resonance imaging with partial volume correction to assess gray matter baseline flow. Cortical thickness was estimated using Freesurfer software, followed by co-registration onto each patient's cerebral blood flow image space. Paired t-tests assessed regional cerebral blood flow in motor cortex (supplied by the carotid artery) and visual cortex (indirectly supplied by the carotid) on the occluded and unoccluded side. Pearson correlations were calculated between cortical thickness and regional cerebral blood flow, along with age, hypertension, diabetes and white matter hyperintensity volume. Multiple regression and generalized estimating equation were used to predict cortical thickness bilaterally and in each hemisphere separately. Cortical blood flow correlated with thickness in motor cortex bilaterally (p = 0.0002), and in the occluded and unoccluded sides individually; age (p = 0.002) was also a predictor of cortical thickness in the motor cortex. None of the variables predicted cortical thickness in visual cortex. Blood flow was significantly lower on the occluded versus unoccluded side in the motor cortex (p<0.0001) and in the visual cortex (p = 0.018). On average, cortex was thinner on the side of occlusion in motor but not in visual cortex. The association between cortical blood flow and cortical thickness in carotid arterial territory with greater thinning on the side of the carotid occlusion suggests that altered cerebral hemodynamics is a factor in cortical thinning.

Progressive Cortical Neuronal Damage and Extracranial-Intracranial Bypass Surgery in Patients with Misery Perfusion

BACKGROUND AND PURPOSE

Misery perfusion may cause selective neuronal damage in atherosclerotic ICA or MCA disease. Bypass surgery can improve misery perfusion and may prevent neuronal damage. On the other hand, surgery conveys a risk for neuronal damage. The purpose of this retrospective study was to determine whether progression of cortical neuronal damage in surgically treated patients with misery perfusion is larger than that in surgically treated patients without misery perfusion or medically treated patients with misery perfusion.

MATERIALS AND METHODS

We evaluated the distribution of benzodiazepine receptors twice by using PET and ¹¹C-labeled flumazenil in 18 surgically treated patients with atherosclerotic ICA or MCA disease (9 with misery perfusion and 9 without) and no perioperative stroke before and after bypass surgery; in 8 medically treated patients with misery perfusion and no intervening ischemic event; and in 7 healthy controls. We quantified abnormal decreases in the benzodiazepine receptors of the cerebral cortex within the MCA distribution and compared changes in the benzodiazepine receptor index among the 3 groups.

RESULTS

The change in the benzodiazepine receptor index in surgically treated patients with misery perfusion (27.5 ± 15.6) during 7 ± 5 months was significantly larger than that in surgically treated patients without misery perfusion (-5.2 ± 9.4) during 6 ± 4 months (P < .001) and in medically treated patients with misery perfusion (3.2 ± 15.4) during 16 ± 6 months (P < .01).

CONCLUSIONS

Progression of cortical neuronal damage in surgically treated patients with misery perfusion and no perioperative stroke may occur and may be larger than that in medically treated patients with misery perfusion and no intervening ischemic event.

Impaired Collateral Flow Compensation During Chronic Cerebral Hypoperfusion in the Type 2 Diabetic Mice

BACKGROUND AND PURPOSE

The presence of collaterals is associated with a reduced risk of stroke and transient ischemic attack in patients with steno-occlusive carotid artery disease. Although metabolic syndrome negatively impacts collateral status, it is unclear whether and to what extent type 2 diabetes mellitus affects cerebral collateral flow regulation during hypoperfusion.

METHODS

We examined the spatial and temporal changes of the leptomeningeal collateral flow and the flow dynamics of the penetrating arterioles in the distal middle cerebral artery and anterior cerebral artery branches over 2 weeks after unilateral common carotid artery occlusion (CCAO) using optical coherent tomography in db/+ and db/db mice. We also assessed the temporal adaptation of the circle of Willis after CCAO by measuring circle of Willis vessel diameters.

RESULTS

After unilateral CCAO, db/db mice exhibited diminished leptomeningeal collateral flow compensation compared with db/+ mice, which coincided with a reduced dilation of distal anterior cerebral artery branches, leading to reduced flow not only in pial vessels but also in penetrating arterioles bordering the distal middle cerebral artery and anterior cerebral artery. However, no apparent cell death was detected in either strain of mice during the first week after CCAO. db/db mice also experienced a more severe early reduction in the vessel diameters of several ipsilateral main feeding arteries in the circle of Willis, in addition to a delayed post-CCAO adaptive response by 1 to 2 weeks, compared with db/+ mice.

CONCLUSIONS

Type 2 diabetes mellitus is an additional risk factor for hemodynamic compromise during cerebral hypoperfusion, which may increase the severity and the risk of stroke or transient ischemic attack.

Progressive Cortical Neuronal Damage and Chronic Hemodynamic Impairment in Atherosclerotic Major Cerebral Artery Disease

Background and Purpose—

Cross-sectional studies suggest that chronic hemodynamic impairment may cause selective cortical neuronal damage in patients with atherosclerotic internal carotid artery or middle cerebral artery occlusive disease. The purpose of this longitudinal study was to determine whether the progression of cortical neuronal damage, evaluated as a decrease in central benzodiazepine receptors (BZRs), is associated with hemodynamic impairment at baseline or hemodynamic deterioration during follow-up.

Methods—

We evaluated the distribution of BZRs twice using positron emission tomography and 11 C-flumazenil over time in 80 medically treated patients with atherosclerotic internal carotid artery or middle cerebral artery occlusive disease that had no ischemic episodes during follow-up. Using 3D stereotactic surface projections, we quantified abnormal decreases in the BZRs in the cerebral cortex within the middle cerebral artery distribution and correlated changes in the BZR index with the mean hemispheric values of hemodynamic parameters obtained from 15 O gas positron emission tomography.

Results—

In the hemisphere affected by arterial disease, the BZR index in 40 patients (50%) was increased during follow-up (mean 26±20 months). In multivariable logistic regression analyses, increases in the BZR index were associated with the decreased cerebral blood flow at baseline and an increased oxygen extraction fraction during follow-up. Increases in the oxygen extraction fraction during follow-up were associated with a lack of statin use.

Conclusions—

In patients with atherosclerotic internal carotid artery or middle cerebral artery disease, the progression of cortical neuronal damage was associated with hemodynamic impairment at baseline and hemodynamic deterioration during follow-up. Statin use may be beneficial against hemodynamic deterioration and therefore neuroprotective.

Normobaric hyperoxia markedly reduces brain damage and sensorimotor deficits following brief focal ischaemia

'True' transient ischaemic attacks are characterized not only clinically, but also radiologically by a lack of corresponding changes on magnetic resonance imaging. During a transient ischaemic attack it is assumed that the affected tissue is penumbral but rescued by early spontaneous reperfusion. There is, however, evidence from rodent studies that even brief focal ischaemia not resulting in tissue infarction can cause extensive selective neuronal loss associated with long-lasting sensorimotor impairment but normal magnetic resonance imaging. Selective neuronal loss might therefore contribute to the increasingly recognized cognitive impairment occurring in patients with transient ischaemic attacks. It is therefore relevant to consider treatments to reduce brain damage occurring with transient ischaemic attacks. As penumbral neurons are threatened by markedly constrained oxygen delivery, improving the latter by increasing arterial O2 content would seem logical. Despite only small increases in arterial O2 content, normobaric oxygen therapy experimentally induces significant increases in penumbral O2 pressure and by such may maintain the penumbra alive until reperfusion. Nevertheless, the effects of normobaric oxygen therapy on infarct volume in rodent models have been conflicting, although duration of occlusion appeared an important factor. Likewise, in the single randomized trial published to date, early-administered normobaric oxygen therapy had no significant effect on clinical outcome despite reduced diffusion-weighted imaging lesion growth during therapy. Here we tested the hypothesis that normobaric oxygen therapy prevents both selective neuronal loss and sensorimotor deficits in a rodent model mimicking true transient ischaemic attack. Normobaric oxygen therapy was applied from the onset and until completion of 15 min distal middle cerebral artery occlusion in spontaneously hypertensive rats, a strain representative of the transient ischaemic attack-prone population. Whereas normoxic controls showed normal magnetic resonance imaging but extensive cortical selective neuronal loss associated with microglial activation (present both at Day 14 in vivo and at Day 28 post-mortem) and marked and long-lasting sensorimotor deficits, normobaric oxygen therapy completely prevented sensorimotor deficit (P < 0.02) and near-completely Day 28 selective neuronal loss (P < 0.005). Microglial activation was substantially reduced at Day 14 and completely prevented at Day 28 (P = 0.002). Our findings document that normobaric oxygen therapy administered during ischaemia nearly completely prevents the neuronal death, microglial inflammation and sensorimotor impairment that characterize this rodent true transient ischaemic attack model. Taken together with the available literature, normobaric oxygen therapy appears a promising therapy for short-lasting ischaemia, and is attractive clinically as it could be started at home in at-risk patients or in the ambulance in subjects suspected of transient ischaemic attack/early stroke. It may also be a straightforward adjunct to reperfusion therapies, and help prevent subtle brain damage potentially contributing to long-term cognitive and sensorimotor impairment in at-risk populations.

[Perfusion criteria of the EICMA efficacy in patients with symptomatic occlusion of the internal carotid artery]

AIM

To investigate changes in cerebral perfusion in patients with unilateral internal carotid artery occlusion before and after surgical revascularization of the brain, depending on the clinical efficacy of surgical treatment.

MATERIAL AND METHODS

The study included 60 patients with unilateral ICA occlusions who underwent placement of an extra-intracranial microvascular anastomosis (EICMA). All patients underwent a CT perfusion study before and after cerebral revascularization. In addition, the degree of neurological deficit was evaluated before surgery and during follow-up (3 and 8-10 months) using the NIHSS score.

RESULTS

All patients were divided into 3 groups, depending on the results of surgical treatment: objective improvement (43 patients), no changes (14 patients), and worsening of clinical symptoms (3 patients). In each group, the absolute and relative perfusion parameters (MTT, CBV, and CBF) were analyzed to identify the perfusion criteria for the EICMA efficacy. A significant relationship between the clinical efficacy of EICMA and a baseline perfusion deficit and its change after anastomosis placement was found.

CONCLUSION

Placement of EICMA is effective treatment for patients with symptomatic ICA occlusions and an increase in the blood transit time in the hemisphere ipsilateral to occlusion by more than 40% compared to that in the opposite side provided that perfusion is recovered in more than one area of the MCA territory (in accordance with the ASPECTS scale).

Increase in [18F]-Fluoroacetate Uptake in Patients With Chronic Hemodynamic Cerebral Ischemia

Background and Purpose—

[18F]-fluoroacetate ( 18 F-FACE) can be used for evaluating glial cell metabolism. Experimental studies have shown an increase in 18 F-FACE uptake in rodent models of cerebral ischemia. The aim of this study was to determine whether 18 F-FACE uptake is increased in the noninfarcted cerebral cortex in patients with hemodynamic ischemia owing to atherosclerotic internal carotid artery or middle cerebral artery disease.

Methods—

We evaluated 9 symptomatic patients with unilateral atherosclerotic internal carotid artery or middle cerebral artery disease and no cortical infarction using positron emission tomography with 18 F-FACE and 15 O-gases. 18 F-FACE uptake during 40 to 60 minutes after injection was compared with the cerebral blood flow, cerebral metabolic rate of oxygen, oxygen extraction fraction, and cerebral blood volume in the middle cerebral artery distributions.

Results—

Significant decreases of cerebral blood flow and cerebral metabolic rate of oxygen and increases of oxygen extraction fraction and cerebral blood volume were found in the hemisphere ipsilateral to the arterial lesion, and 18 F-FACE uptake in this region was greater than that in the contralateral hemisphere. The relative 18 F-FACE uptake (ipsilateral/contralateral ratio) was negatively correlated with cerebral blood flow or cerebral metabolic rate of oxygen values and was positively correlated with oxygen extraction fraction values. Multivariate analysis showed that the ipsilateral/contralateral 18 F-FACE uptake ratio was independently correlated with the cerebral blood flow (or oxygen extraction fraction) and cerebral metabolic rate of oxygen values.

Conclusions—

In patients with atherosclerotic internal carotid artery or middle cerebral artery disease, 18 F-FACE uptake is increased in the noninfarcted cerebral cortex with chronic hemodynamic ischemia characterized by misery perfusion with decreased oxygen metabolism. Increased 18 F-FACE uptake may indicate the cortical regions that are at particular risk for ischemic damage.

Dilatation of the Virchow-Robin spaces as an indicator of unilateral carotid artery stenosis: correlation with white matter lesions

BACKGROUND

Virchow-Robin space (VRS) dilatation is related to many pathologic conditions, mostly associated with vascular abnormalities. White matter lesions (WMLs) are commonly seen on brain magnetic resonance imaging (MRI) with advancing age and generally considered as potential markers for vascular disease.

PURPOSE

To investigate if asymmetric dilatation of VRSs and WMLs are associated with unilateral internal carotid artery stenosis (ICAS) and to test the relationship between dilated VRSs and common vascular risk factors.

MATERIAL AND METHODS

Twenty-nine patients (18 men, 11 women; mean age, 68.62 years) with unilateral ICAS (≥70% carotid stenosis) undergoing carotid endarterectomy were identified for this Health Insurance Portability and Accountability Act (HIPAA) compliant prospective study and assessed with brain MRI. Two experienced radiologists scored VRSs and WMLs and evaluated old infarcts, chronic lacunar infarcts, and cerebral atrophy. Asymmetry of WML and VRS scores between two cerebral hemispheres was assessed and associations between VRS scores, WML scores, and explanatory variables (e.g. age, sex, vascular risk factors, and atrophy) were tested.

RESULTS

In this study, WMLs and basal ganglia VRSs were significantly greater in the unilateral hemisphere with ICA stenosis than contralateral hemisphere. Basal ganglia VRSs were associated with WMLs and internal cerebral atrophy. No association between the severity of VRSs and vascular risk factors was found.

CONCLUSION

ICA stenosis may contribute as a factor in the development of WMLs and dilatation of VRSs by causing chronic hypoperfusion. VRS dilatation may be an additional MRI marker of ICAS.

Selective neuronal loss in ischemic stroke and cerebrovascular disease

As a sequel of brain ischemia, selective neuronal loss (SNL)-as opposed to pannecrosis (i.e. infarction)-is attracting growing interest, particularly because it is now detectable in vivo. In acute stroke, SNL may affect the salvaged penumbra and hamper functional recovery following reperfusion. Rodent occlusion models can generate SNL predominantly in the striatum or cortex, showing that it can affect behavior for weeks despite normal magnetic resonance imaging. In humans, SNL in the salvaged penumbra has been documented in vivo mainly using positron emission tomography and (11)C-flumazenil, a neuronal tracer validated against immunohistochemistry in rodent stroke models. Cortical SNL has also been documented using this approach in chronic carotid disease in association with misery perfusion and behavioral deficits, suggesting that it can result from chronic or unstable hemodynamic compromise. Given these consequences, SNL may constitute a novel therapeutic target. Selective neuronal loss may also develop at sites remote from infarcts, representing secondary 'exofocal' phenomena akin to degeneration, potentially related to poststroke behavioral or mood impairments again amenable to therapy. Further work should aim to better characterize the time course, behavioral consequences-including the impact on neurological recovery and contribution to vascular cognitive impairment-association with possible causal processes such as microglial activation, and preventability of SNL.

Characterizing infarction and selective neuronal loss following temporary focal cerebral ischemia in the rat: a multi-modality imaging study

BACKGROUND AND PURPOSE

Current models dictate that, depending on occurrence of early reperfusion, the ischemic penumbra either undergoes or escapes infarction (i.e., "pan-necrosis"). However, tissue outcome following temporary middle-cerebral artery occlusion (tMCAo) in rodents can also include selective neuronal loss (SNL), which even if subtle may impede functional recovery. In order to explore the pathophysiology of ischemic stroke, determine potential therapeutic targets and monitor effects of therapy, in vivo imaging surrogates of these varied histopathological outcomes applicable in the clinical setting would be useful. Although hyperintense signal on T(2)-weighted MRI in the chronic post-stroke stage is considered a reliable surrogate of tissue infarction, SNL is not associated with T(2)W abnormal signal. In the clinical setting, the neuron-specific PET ligand (11)C-flumazenil (FMZ) has been used to identify both pan-necrosis and peri-infarct SNL, but this inference has not been histopathological confirmed so far. Here we investigated the late tissue sequelae of tMCAo in the rodent using in vivo T(2)W MRI and FMZ-PET against post mortem immunohistochemistry as gold standard.

METHODS

Adult spontaneously hypertensive rats (SHRs) underwent 45 min distal-clip middle-cerebral artery occlusion and, 28 days later, FMZ-PET and T(2)W-MRI, immediately followed by immunohistochemistry for neuronal loss (NeuN), activated microglia and astrocytosis. Based on standard histopathological definitions, ischemic lesions were classified into pan-necrosis, partial infarction or SNL. NeuN changes and FMZ binding across the whole hemisphere were quantified in the same set of 44 regions-of-interest according to previously validated protocols; linear regressions between these two measures were carried out both within and across subjects.

RESULTS

Both cortical pan-necrosis/partial infarction and SNL were present in all rats except one, where SNL was isolated and extensive. Infarction/partial infarction, but not SNL, was associated with T(2)W hyperintense signals and cortical atrophy. In contrast, FMZ binding was decreased in all types of lesions including SNL, in proportion with NeuN staining intensity both within (p<0.05 to <0.001) and across (p<0.001) subjects, including the subject that showed pure SNL (p=0.01).

CONCLUSION

This novel study revealed three main facts: i) long-term histopathological cortical changes following 45 min tMCAo in SHRs included all three of SNL, partial infarction and frank infarction; ii) T2W MRI showed conspicuous high signal lesions for complete or partial infarction, but no changes for SNL; and iii) FMZ-PET was sensitive to all three types of tMCAo-induced histopathological changes, including isolated SNL, suggesting it is a valid surrogate for the histological sequelae of focal cerebral ischemia. In addition, the finding of almost universal completed cortical infarction at 28 days differed from our previous findings at 14-day survival using the same model and rat strain, where SNL was the almost exclusive outcome, possibly representing delayed infarct maturation. Prospective studies are needed to investigate this interesting possibility.

Reproducibility of cerebral blood flow assessment using a quantitative SPECT reconstruction program and split-dose 123I-iodoamphetamine in institutions with different γ-cameras and collimators

Single photon emission computed tomography (SPECT) is used widely in clinical studies. However, the technique requires image reconstruction and the methods for correcting scattered radiation and absorption are not standardized among SPECT procedures. Therefore, quantitation of cerebral blood flow (CBF) may not be constant across SPECT models. The quantitative SPECT (QSPECT) software package has been developed for standardization of CBF. Using the QSPECT/dual-table autoradiographic (DTARG) method, CBF and cerebral vascular reactivity (CVR) at rest and after acetazolamide challenge can be evaluated using (123)I-iodoamphetamine in a single SPECT session. In this study, we examined the reproducibility of quantitative regional CBF and CVR in QSPECT/DTARG using different SPECT models at two facilities. The subjects were nine patients with chronic cerebral ischemic disease who underwent QSPECT/DTARG at both facilities with use of different γ-cameras and collimators. There were significant correlations for CBF at rest and after acetazolamide challenge measured at the two facilities. The consistency of the CBFs of the patients measured at the two facilities were good in all cases. Our results show that CBF measured by QSPECT/DTARG in the same patients is reproducible in different SPECT models. This indicates that standardized evaluation of CBF can be performed in large multicenter studies.

Cerebral hemodynamics and cognitive impairment: baseline data from the RECON trial

OBJECTIVE

To determine whether unihemispheral hemodynamic failure is independently associated with cognitive impairment among participants in the National Institute of Neurological Disorders and Stroke-sponsored, multicenter, randomized clinical trial, Randomized Evaluation of Carotid Occlusion and Neurocognition (RECON).

METHODS

Forty-three patients were randomized into RECON after recent symptomatic carotid artery occlusion and asymmetrically increased oxygen extraction fraction (OEF) by PET (OEF ratio >1.13), indicating stage II hemodynamic failure on the side of occlusion. The PET-positive patients were compared with 28 RECON-enrolled patients who met all clinical and radiographic inclusion/exclusion criteria but had no OEF asymmetry. A multivariable regression compared patients with PET OEF >1.13 or ≤1.13, stratifying by TIA vs. stroke as the qualifying event. The dependent variable was a composite neurocognitive score derived from averaging age-normalized z scores on a test battery that included global and internal carotid artery (ICA) side-relevant hemisphere-specific tests.

RESULTS

There were no differences in demographic, clinical, or radiologic characteristics between the PET-positive and PET-negative patients except for PET OEF asymmetry. The unadjusted average neurocognitive z score was -1.45 for the PET-positive and -1.25 for the PET-negative patients, indicating cognitive impairment in both groups but no difference between them (p = 0.641). After adjustment for age, education, side of occlusion, depression, and previous stroke, there was a significant difference between PET-positive and PET-negative patients among those with TIA as a qualifying event (average z score = -1.41 vs. -0.76, p = 0.040). Older age and right ICA side were also significant in this model.

CONCLUSION

Hemodynamic failure is independently associated with cognitive impairment in patients with carotid occlusion. This finding establishes the physiologic parameter upon which the extracranial-intracranial bypass will be tested.

Focal neuronal damage in patients with neuropsychological impairment after diffuse traumatic brain injury: evaluation using ¹¹C-flumazenil positron emission tomography with statistical image analysis

This study was conducted to identify the regional neuronal damage occurring in patients with neuropsychological impairment following diffuse traumatic brain injury (TBI) compared with normal control subjects. In addition, measures of the neuropsychological tests were correlated with regional ¹¹C-flumazenil (FMZ) binding potential (BP) reductions to clarify the relationship between cognitive impairment and regional neuronal damage. We performed ¹¹C-flumazenil positron emission tomography (FMZ-PET) studies using three-dimensional stereotactic surface projection (3D-SSP) statistical image analysis in eight diffuse axonal injury (DAI) patients (mean age 29.1 ± 11.1 years, range 19-46 years). All patients underwent assessment with the Wechsler Adult Intellectual Scale-Third Edition (WAIS-III) to evaluate general intelligence. Twenty healthy control subjects (mean age 24.4 ± 2.8 years, range 22-30 years) were also studied to obtain a normal database for 3D-SSP. Group comparisons showed significant regional low FMZ uptake in the bilateral medial frontal gyri, the anterior cingulate gyri, and the thalamus. Individual analysis also showed decreased FMZ uptake in these regions; however, the distribution and extent of low FMZ uptake were different in each individual patient. Full-scale IQ (FIQ) and performance IQ (PIQ) negatively correlated with the degree of FMZ BP reduction (BZR index) in the right thalamus. FIQ, verbal IQ (VIQ), and PIQ also negatively correlated with the BZR index in the left medial frontal gyrus. DAI uniformly induced neuronal damage in the medial frontal cortex and the thalamus, which may be related to underlying cognitive impairments in diffuse TBI patients. Future studies to confirm a common area of focal neuronal damage and a direct correlation with neuropsychological testing may validate the use of FMZ-PET for the functional diagnosis of neuropsychological impairments after TBI.

Silent cortical neuronal damage in atherosclerotic disease of the major cerebral arteries

In atherosclerotic internal carotid artery (ICA) or middle cerebral artery (MCA) disease, hemodynamic compromise may cause selective neuronal damage manifested as loss of central benzodiazepine receptors (BZRs) in the normal-appearing cerebral cortex, without overt episode of stroke. To investigate the association of decreases in cortical BZRs with hemodynamic compromise and the effect of angiotensin receptor blockers (ARBs) on these receptors in patients whose atherosclerotic ICA or MCA disease is asymptomatic, we measured BZRs using positron emission tomography and (11)C-flumazenil in 79 patients with asymptomatic atherosclerotic ICA or MCA disease and no cortical infarction. Three-dimensional stereotactic surface projections were used to calculate the BZR index, a measure of abnormally decreased BZRs in the cerebral cortex within the MCA distribution. Multiple regression analysis showed this index to be positively correlated with the value of oxygen extraction fraction, with the presence of silent subcortical infarcts, and with the presence of ischemic heart disease, whereas it was negatively correlated with the treatment of hypertension with ARBs. In asymptomatic atherosclerotic ICA or MCA disease, hemodynamic compromise is associated with selective neuronal damage manifested as decreases in cortical BZRs in the noninfarcted cerebral cortex, whereas ARBs are associated with preservation of cortical BZRs.

Selective neuronal damage and Wisconsin Card Sorting Test performance in atherosclerotic occlusive disease of the major cerebral artery

BACKGROUND

In atherosclerotic internal carotid artery (ICA) or middle cerebral artery (MCA) disease, selective neuronal damage can be detected as a decrease in central benzodiazepine receptors (BZRs) in the normal-appearing cerebral cortex. This study aimed to determine whether a decrease in the BZRs in the non-infarcted cerebral cortex is associated with poor performance on the Wisconsin Card Sorting Test (WCST), which assesses executive functions.

METHODS

The authors measured the BZRs using positron emission tomography and (11)C-flumazenil in 60 non-disabled patients with unilateral atherosclerotic ICA or MCA disease and no cortical infarction. Using three-dimensional stereotactic surface projections, the abnormally decreased BZR index (extent (%) of pixels with Z score >2 compared with controls × average Z score in those pixels) in the cerebral cortex of the anterior cerebral artery (ACA) or MCA territory was calculated and found to be correlated with the patient's score on the WCST.

RESULTS

On the basis of the WCST results, 39 patients were considered abnormal (low categories achieved) for their age. The BZR index of the ACA territory in the hemisphere affected by arterial disease was significantly higher in abnormal patients than in normal patients. The BZR index of the MCA territory differed significantly between the two groups when patients with left arterial disease (n=28) were analysed separately.

CONCLUSIONS

In atherosclerotic ICA or MCA disease, selective neuronal damage that is manifested as a decrease in BZRs in the non-infarcted cerebral cortex may contribute to the development of executive dysfunction.

Regional partition coefficient of water in patients with cerebrovascular disease and its effect on rCBF assessment

OBJECTIVE

Cerebral blood flow (CBF) estimation with C15O2 PET usually assumes a single tissue compartment model and a fixed brain-blood partition coefficient of water. However, the partition coefficient may change in pathological conditions. The purpose of this study was to investigate the changes in the partition coefficient of water in pathological regions and its effect on regional CBF assessment.

METHODS

The study protocol included 22 patients with occlusive cerebrovascular disease to compare the partition coefficients among three regions (infarction area, noninfarct hypoperfusion area, and contralateral area) in the pathological brain (analysis A), and to compare the CBF estimated by using a fixed partition coefficient and CBF estimated using floating partition coefficients (analysis B).

RESULTS

The partition coefficient in the infarction area (0.55±0.07 ml/g) was lower than that in the contralateral normal cortex (0.68±0.05 ml/g), whereas noninfarct hypoperfusion area did not show a significant change (0.67±0.06 ml/g). As a result, the use of a fixed partition coefficient of normal volunteers (0.70 ml/g) resulted in an underestimation in regional CBF by 12% in infarction area (P<0.05), whereas the estimation errors were smaller and induced no significant difference in the noninfarct hypoperfusion area or in contralateral areas.

CONCLUSION

The partition coefficient is stable except for the infarction area, and CBF estimation using a fixed partition coefficient of normal volunteers provides clinically appreciable information in patients with cerebrovascular disease.

PET in Cerebrovascular Disease

Investigation of the interplay between the cerebral circulation and brain cellular function is fundamental to understanding both the pathophysiology and treatment of stroke. Currently, PET is the only technique that provides accurate, quantitative in vivo regional measurements of both cerebral circulation and cellular metabolism in human subjects. We review normal human cerebral blood flow and metabolism and human PET studies of ischemic stroke, carotid artery disease, vascular dementia, intracerebral hemorrhage and aneurysmal subarachnoid hemorrhage and discuss how these studies have added to our understanding of the pathophysiology of human cerebrovascular disease.

Hemodynamic Compromise as a Cause of Internal Border-Zone Infarction and Cortical Neuronal Damage in Atherosclerotic Middle Cerebral Artery Disease

Background and Purpose— Hemodynamic compromise due to atherosclerotic middle cerebral artery (MCA) disease may induce internal border-zone infarction and cortical neuronal damage. This study aimed to determine whether internal border-zone infarction is associated with increased oxygen extraction fraction (OEF) and a decrease in central benzodiazepine receptors (BZRs) in the overlying cerebral cortex in atherosclerotic MCA disease.

Methods— We measured the OEF by using positron emission tomography and 15 O gas in 100 nondisabled patients with atherosclerotic MCA disease in the chronic stage. On MRI, the infarcts were categorized as territorial, border-zone (external or internal), deep perforator, and superior perforator infarcts. In 62 patients, BZRs were measured using 11 C-flumazenil. By using 3-dimensional stereotactic surface projections, the abnormally decreased BZR index (“BZR index”) [(the extent of the pixels with Z score more than 2 compared with controls)×(average Z score in those pixels)] was calculated. In the hemisphere affected by MCA disease, the type of infarcts was correlated with the value of OEF or BZR index in the cerebral cortex of the MCA distribution.

Results— Compared with patients without internal border-zone infarcts, those with these infarcts (n=18) had significantly increased OEF and significantly high BZR index. Multivariate analysis revealed that internal border-zone infarction was independently associated with increased OEF and high BZR index.

Conclusions— In atherosclerotic MCA disease, internal border-zone infarction is associated with increased OEF and a decrease in BZRs in the overlying cerebral cortex, suggesting that hemodynamic compromise may induce internal border-zone infarction and cortical neuronal damage.