Can a closed carotid artery be reopened?

Carotid occlusion is a disease that presents a difficult decision for the treating provider. Traditionally, many providers would opt for expectant management with risk factor reduction and supportive therapy. There is a growing body of literature however pointing to possible improved outcomes of more aggressive treatments, including reopening of the occluded carotid. In this review, we discuss the difficulties involved in diagnosing a patient presenting with symptomatic carotid occlusion, the natural history of the disease, and the emerging treatment options and paradigms of different institutions based on recent literature.

Embolic and Hemodynamic Transcranial Doppler Characteristics in Patients with Acute Ischemic Stroke due to Carotid Occlusive Disease: Contribution to the Different Infarct Patterns on MRI

BACKGROUND AND PURPOSE

Whether hemodynamic and/or embolic transcranial Doppler (TCD) features of internal carotid artery (ICA) stenosis contribute to the classification of stroke patterns on MRI.

PATIENTS AND METHODS

Consecutive patients presenting symptomatic ≥50% ICA stenosis were included. Microembolic signals (MES) detection and measurement of cerebral vasoreactivity (VR) were performed by TCD. Only acute MRI lesions, territorial (TT) and/or borderzone (BZ) were considered.

RESULTS

A total of 72 ICA stenoses, 27 (38%) moderate (50-69%), and 45 (62%) high grade (70-99%) were included. MRI lesions showed 32 (44%) pure TT, 20 (28%) pure BZ, and 20 (28%) mixed TT and BZ. Impaired VR was found more frequently among patients with higher degrees of stenoses (P < .001) whereas MES were similarly encountered in both groups (P = NS). Impaired VR was more common in the BZ (10/20, 50%) than in the TT group (9/32, 28%, P < .1) while MES were present in 47% (15/32) of patients with TT and in 30% (6/20, P < .1) of those with BZ lesions, in particular in cortical BZ infarcts (P < .02).

CONCLUSION

Our findings suggest that TCD characteristics of the ICA stenosis contribute to better define stroke patterns on MRI in about one-third of the patients presenting with pure TT or BZ lesions.

Progressive changes in cerebral perfusion after carotid stenting: a dynamic susceptibility contrast perfusion weighted imaging study

BACKGROUND

We aimed to assess baseline inter-hemispheric perfusion differences, before carotid artery stenting (CAS), of severe internal carotid artery (ICA) stenosis, and to evaluate perfusion changes over time after CAS by means of perfusion weighted imaging (PWI).

METHODS

Dynamic susceptibility contrast PWI was performed in 33 patients with severe ICA stenosis 1 day before and 1 day after CAS, and repeated in 23 patients 30 days after CAS. Cerebral blood volume, cerebral blood flow, arrival time (T0), mean transit time, and time to peak (TTP) relative values comparing symptomatic and asymptomatic hemispheres before CAS were obtained. Pre- and post-CAS values were also compared in the treated hemisphere and middle cerebral artery (MCA) territories. The influence of collateral circulation and contralateral ICA stenosis were evaluated.

RESULTS

Before CAS, TTP was significantly increased in the affected hemisphere and MCA territory in all patients (p=0.007 and p=0.021, respectively). After treatment, normalization was observed for TTP and T0 30 days after CAS in all patients, mainly in patients with any grade of contralateral stenosis and with one or both functioning communicating arteries (42.4% of patients had both, and 42.4% showed only one-anterior communicating artery=11 patients (78.6%) and posterior communicating artery=3 patients (21.4%)).

CONCLUSIONS

Inter-hemispheric perfusion differences in patients with severe ICA stenosis normalize after CAS in the long term, up to 30 days after the procedure.

Which CT perfusion parameter best reflects cerebrovascular reserve?: correlation of acetazolamide-challenged CT perfusion with single-photon emission CT in Moyamoya patients

BACKGROUND AND PURPOSE

CT perfusion (CTP) is a more readily accessible method for evaluation of cerebral perfusion than single-photon emission CT (SPECT). We assessed whether there is any resting or drug-challenged CTP parameter correlating with cerebrovascular reserve (CVR) obtained by SPECT in Moyamoya patients.

MATERIALS AND METHODS

Normalized baseline CTP parameters and their percentage changes were calculated in 152 regions of interest (ROIs). On qualitative SPECT analysis, each ROI was classified in either the "impaired CVR" or "normal CVR" group. Quantitative CVR was calculated by using normalized SPECT values before and after acetazolamide administration. Baseline CTP parameters and their percentage changes were compared with qualitative and quantitative CVRs. Receiver operating characteristic (ROC) curve analysis defined the threshold values of CTP parameters that best predict impaired qualitative CVR.

RESULTS

The mean values of CTP parameters were significantly different between normal and impaired CVR groups. The percentage change of cerebral blood flow (pcCBF) was correlated most significantly with quantitative CVR (r = 0.89; P < .05). The correlation coefficients between the baseline CTP parameters and quantitative CVR were poor or not significant. The ROC-derived threshold values of pcCBF and mean transit time determined impaired CVR with a sensitivity of 94.4 and 85.2; specificity of 93.2 and 65.9; positive predictive value of 97.1 and 86.0; and negative predictive value of 87.2 and 64.4, respectively.

CONCLUSION

Baseline CTP parameters are not reliable for predicting impaired CVR. However, pcCBF correlated strongly with quantitative CVR; therefore, CTP evaluation for CVR in Moyamoya patients requires normalization and acetazolamide challenge.

Quantitative cerebrovascular reserve measured by acetazolamide-challenged dynamic CT perfusion in ischemic adult Moyamoya disease: initial experience with angiographic correlation

BACKGROUND AND PURPOSE

CT perfusion is a much more readily accessible imaging method to assess cerebral hemodynamic status than single-photon emission CT. We prospectively assessed quantitative cerebrovascular reserve by using acetazolamide (ACZ)-challenged CT perfusion for evaluating hemodynamic impairment in ischemic adult Moyamoya disease and compared it with angiographic findings.

MATERIALS AND METHODS

Sixteen adult patients with ischemic Moyamoya disease and 12 age-matched normal control subjects underwent both ACZ-challenged CT perfusion and digital subtraction angiography. Normalized baseline hemodynamic parameters and their percent changes (PCs) were calculated in 56 hemispheres. We classified the degrees of distal carotid artery stenosis according to modified Suzuki stage and determined the presence of basal Moyamoya vessels (BMVs). The values of normalized parameters and their PCs were compared with angiographic findings.

RESULTS

Normalized baseline mean transit time (MTT) and PC of normalized cerebral blood flow (CBF) were significantly correlated with angiographic stages in all of the vascular territories; however, the correlation coefficient of the normalized baseline MTT was lower than that of the PC of CBF. In the external borderzone and the middle cerebral arterial territory, the hemispheres with extensive BMVs exhibited significantly lower PC values of CBF and significantly higher normalized baseline MTT values than those in hemispheres with diminished BMVs and in normal control subjects.

CONCLUSION

Among the hemodynamic parameters measured by ACZ-challenged CT perfusion, the PC of CBF correlated highly significantly with angiographic stage; however, the normalized baseline CT perfusion parameters showed weak or no significant correlation.

Changes in cerebral hemodynamics after carotid stenting: evaluation with CT perfusion studies

PURPOSE

To determine changes in cerebral perfusion parameters, based on CT perfusion imaging, in patients after unilateral transluminal angioplasty and stent placement.

MATERIAL AND METHODS

74 patients with symptomatic high - grade internal carotid artery stenosis (>70%) were studied with CT perfusion imaging before and - on average - 70 hours and 172 days after carotid stent placement. There were 50 patients with unilateral carotid artery stenosis and 24 with stenosis and accompanying contralateral internal carotid artery occlusion. CT examination was performed using a multidetector helical CT scanner (Light Speed Ultra Advantage, GE Healthcare, USA). Maps showing the absolute values of cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) were generated.

RESULTS

In a group with unilateral carotid artery stenosis perfusion deficits were present in 84% of patients, ipsilaterally to stenosis. MTT elongation was noted (6.2-6.8s) together with decreased values of CBF (40-46ml/100g/min) and slightly increased CBV (3.2ml/100g). In this group, 3 days after stenting, 30% of patients had perfusion deficits, and after 6 months only 6%. In a group with carotid artery stenosis and contralateral artery occlusion severe perfusion deficits were noted in both hemispheres and they were present in 100% of patients. 6 months after stenting hypoperfusion was observed only in 17% of patients.

CONCLUSIONS

Brain perfusion deficits, observed in a majority of patients with carotid artery stenosis tend to improve considerably after carotid artery stenting, in long - term follow up.

Construction and evaluation of an average CT brain image for inter-subject registration

An average CT brain image is constructed to serve as reference frame for inter-subject registration. A set of 96 clinical CT images is used. Registration includes translation, rotation, and anisotropic scaling. A temporary average based on a subset of 32 images is constructed. This image is used as reference for the iterative construction of the average CT image. This approach is computationally efficient and results in a consistent registration of the 96 images. Registration of new images to the average CT is more consistent than registration to a single CT image. The use of the average CT image is illustrated.

Analysis of cerebral infarction pattern in computed tomography images of patients with internal carotid artery stenosis

RATIONALE AND OBJECTIVES

An unbiased and quantitative analysis of lesion patterns in patient groups is described and applied to the analysis of infarction patterns.

MATERIALS AND METHODS

One hundred forty-two computed tomographic images of patients with ischemic stroke were registered to an average computed tomographic brain image, which was used as template. Lesions were segmented manually and averaged per category of internal carotid artery (ICA) stenosis. Thus, patterns of lesion distribution were formed. Differences then were analyzed using nonparametric statistics. This analysis was compared with the traditional classification of lesions.

RESULTS

The nonparametric analysis showed an increased involvement of the territory of the middle cerebral artery in infarctions in patients with ICA occlusion compared with patients with mild or severe ICA stenosis. These differences did not show when classification of infarctions was used.

CONCLUSIONS

The presented method is more sensitive to differences in lesion patterns than traditional lesion classification and showed a different infarction pattern for ICA occlusion.

Cerebral bloodflow and oxygen metabolism in borderzone and territorial infarcts due to symptomatic carotid artery occlusion

It remains controversial whether borderzone infarcts are due to compromised cerebral perfusion and whether territorial infarcts are caused by artery-to-artery emboli in case of occlusion of the internal carotid artery. The present positron emission tomography study compares with normal controls, the average regional cerebral bloodflow (rCBF), regional oxygen extraction fraction (rOEF) and regional cerebral metabolic rate for oxygen (rCMRO(2)) in the infarct area, the peri-infarct zone, the remaining homolateral hemisphere and in the contralateral hemisphere of 10 patients with borderzone and 17 patients with territorial infarcts, due to internal carotid artery occlusion by atherosclerosis and by cervical dissection. The steady-state technique with oxygen-15 was used. A nearly significant increase of rOEF with lowered rCBF and rCMRO(2) was observed in the peri-infarct zone of patients with territorial infarcts. In patients with borderzone infarcts rCMRO(2) was decreased in the peri-infarct zone, in the remaining homolateral hemisphere and in the contralateral hemisphere without changes in rCBF and rOEF. The present study finds no arguments that impaired cerebral perfusion is a more frequent cause of borderzone than of territorial infarcts.

Cobalt-55 positron emission tomography in symptomatic atherosclerotic carotid artery disease: borderzone versus territorial infarcts

BACKGROUND

Borderzone as well as territorial infarcts can occur in severe atherosclerotic carotid artery disease. It remains controversial whether the borderzone distribution of infarcts is due to hypoperfusion or due to artery-to-artery embolism.

PURPOSE

The present study investigates whether cobalt-55 (55Co) positron emission tomography (PET) shows a different pattern of ischaemia according to the topography of the infarct in severe atherosclerotic carotid artery disease.

PATIENTS AND METHODS

Five patients with a cortical borderzone and seven with a territorial infarct, due to symptomatic carotid artery disease, were investigated with 55Co PET 3-6 months after stroke. Average 55Co counts in the infarct area, the adjacent cortical zone, the deep white matter and, contralateral cerebral cortex and white matter, were compared to the values in the cerebellum used as reference.

RESULTS

No differences in 55Co ratio were observed in the different regions of interest (ROIs) between patients with cortical borderzone and those with territorial infarcts. The 55Co uptake was similar or lower than the reference value for all ROIs in all individual patients.

CONCLUSION

In patients with borderzone as well as with territorial infarcts no evidence was found for subclinical ischaemic injury in or around the infarcts. These data do support the conclusion that cortical borderzone infarcts may not be due to ongoing chronic haemodynamic impairment, but by no means is this conclusive evidence.

Internal borderzone infarction: a marker for severe stenosis in patients with symptomatic internal carotid artery disease. For the North American Symptomatic Carotid Endarterectomy (NASCET) Group

BACKGROUND AND PURPOSE

Among subcortical infarctions, internal borderzone infarcts (IBI) are considered to be separate entities from perforating artery infarcts (PAI). The purpose of the present study is to examine the relationship between the presence of IBI and the degree of angiographically defined internal carotid artery (ICA) stenosis in symptomatic patients.

METHODS

A review of 1253 brain CTs from patients recruited by the North American Symptomatic Carotid Endarterectomy Trial was performed, using templates for the identification of subcortical and cortical vascular territories.

RESULTS

A total of 413 patients had visible ischemic lesions on the side ipsilateral to their symptomatic ICA. Of these, 138 had PAI, 108 had IBI, 122 had cortical infarcts, and 45 had a combination of different lesions. Mean (+/-SD) lesion diameter was larger for IBI (11.0+/-5.9 mm) than for PAI (7.1+/-4.7 mm) (P<0.001 for comparing 2 means). IBI was associated with higher degrees of ICA stenosis (P<0. 001). Sixty-three percent of the patients with IBI had severe (70% to 99%) ICA stenosis compared with 42% of patients with PAI; 18% of the IBI patients had stenosis of 90% or more compared with 8% of the patients with PAI. Multiple logistic regression did not identify any patient characteristics as confounders.

CONCLUSIONS

Among subcortical infarctions, IBI are associated with higher degrees of ICA stenosis in symptomatic patients. Differentiating between internal borderzone and perforating artery infarcts is important, because each may arise from different mechanisms, namely, carotid disease and small-vessel disease, respectively.

Carotid disease in acute stroke: A review

This article reviews the literature about carotid disease in acute stroke. Several conclusions are drawn. First, carotid disease is an important cause of ipsilateral cortical strokes, with significant ipsilateral disease found in about one fourth of patients. Second, the role of carotid disease in lacunar stroke is less certain but probably causes a small number of lacunar infarcts. Third, the majority of infarcts that occur with severe carotid stenosis or acute carotid occlusion are caused by cerebral emboli, whereas most infarcts with preexisting occlusion are probably caused by hemodynamic factors. Fourth, the optimal timing of carotid surgery in acute stroke is uncertain. Clinical trials of endarterectomy in acute stroke are now required.

Preliminary clinical-radiological assessment of a MR tissue signature model in human stroke

We evaluated the ability of an MR signature model (SM) of cerebral ischemic injury to stage the evolution of cellular damage in human stroke. In 19 patients with ischemic stroke of presumed embolic or non-embolic cause we carried out diffusion-weighted and T2-weighted MR imaging within 48 h of onset, and obtained apparent diffusion coefficient of water (ADCw), and T2 weighted images. We used the signatures obtained from these ADCw/T2 maps to formulate two patterns of damage signifying accelerated or non-accelerated progression of cellular death after stroke onset. Those patients with the accelerated pattern corresponded to those with the neuroradiological (NRC) and clinical diagnosis (TOAST.1 and TOAST.2) of presumed embolic stroke, with clinical diagnosis performed blinded both to NRC and to SM. Agreement between the SM and NRC was substantial (kappa=0.62), moderate (0.60<kappa<0.40) between the SM or NRC and TOAST.2, and fair (0.40<kappa<0.20) among the SM or NRC and TOAST.1. We believe these results constitute a preliminary validation of the MR tissue signature modeling in clinical stroke assessment.

Symptomatic carotid artery occlusion. A reappraisal of hemodynamic factors

BACKGROUND

Over the last several years evidence has accumulated that in addition to embolism, a compromised cerebral blood flow may play an important role in causing transient ischemic attacks and ischemic stroke in patients with occlusion of the internal carotid artery. This evidence is found in both clinical features and ancillary investigations, particularly measurements of cerebral blood flow.

SUMMARY OF REVIEW

On the basis of 20 follow-up studies in patients with transient ischemic attacks or minor ischemic stroke associated with an occluded carotid artery, the annual risk of stroke was 5.5% (95% confidence interval [CI], 5.0% to 6.0%), and that of ipsilateral stroke (distinguished in 11 of the 20 studies) was 2.1% (95% CI, 1.6% to 2.8%). Patients with a compromised cerebral blood flow as measured by positron emission tomography, single-photon emission CT, transcranial Doppler, or stable xenon CT (six studies) have an even higher annual risk of stroke (all strokes: 12.5%; 95% CI, 8.9% to 17.6%; ipsilateral stroke: 9.5%; 95% CI, 6.4% to 14.0%).

CONCLUSIONS

Because a compromised cerebral blood flow may be an important causal factor in patients with symptomatic carotid artery occlusion, medical and surgical options for treatment are reviewed in this light.