Prevalence and prognostic impact of microembolic signals in arterial sources of embolism

Detection of microemboli in patients with acute ischaemic stroke and atrial fibrillation suggests poor functional outcome

INTRODUCTION

We investigated the burden of microembolic signals (MES) in patients with acute ischaemic stroke (AIS) and atrial fibrillation (AF), assessing their impact on functional outcomes.

PATIENTS AND METHODS

This multicentre international prospective cohort study involved patients with AIS and either a known or newly diagnosed anticoagulant-naïve AF. All centres utilised the same transcranial Doppler machine for 1-h monitoring with bilateral 2 MHz probes within 24 h of symptom onset. Recordings underwent MES analysis by a blinded central reader. The primary objectives were to ascertain the MES proportion and its association with functional outcomes assessed by the modified Rankin scale (mRS) score at 90 days.

RESULTS

Between September 2019 and May 2021, we enrolled 61 patients, with a median age of 78 years (interquartile range 73-83) and a median stroke severity score of 11 (interquartile range 4-18). MES were observed in 14 patients (23%), predominantly unilateral (12/14, 86%), with a median rate of 6 counts/hour (interquartile range 4-18). MES occurrence was higher post-thrombectomy and among those with elevated brain natriuretic peptide levels (p < 0.05). A worse mRS score of 3-6 was more frequent in patients with MES, occurring in 11/14 (79%), compared to those without MES, 20/47 (43%), with an adjusted odds ratio of 5.04 (95% CI, 1.15-39.4), p = 0.04.

CONCLUSIONS

Nearly a quarter of patients with AIS and AF exhibited silent microembolization after the index event. Detecting MES within 24 h post-stroke (using transcranial Doppler) could signify a marker of poor functional outcomes. Subsequent trials will assess if very early antithrombotic treatment might enhance outcomes in this highly selective group of cardioembolic stroke patients. (Clinicaltrials.gov ID: NCT06018090).

High-Intensity Transient Signals Detected in a Renal Allograft

High-intensity transient signals (HITS) are signals recorded by the Doppler ultrasounds, reflecting either the passage of microemboli, both solid or gaseous in the vessels, or artifacts. Their identification during Duplex US highlights the need for further evaluation to rule out a potential embolic source. A 49-year-old female was referred to our hospital for renal transplantation. The Doppler ultrasound done on day 4 after the surgery revealed the presence of high-intensity transient signals (HITS) suggesting the passage of an emboli. Renal magnetic resonance angiography (MRA) confirmed the presence of peripheral parenchymal defects suggestive of a distal embolus. A better understanding and recognition of this radiological sign are essential in order to initiate appropriate patient management when needed. In this report, we review the importance of HITS and present a case in which HITS were detected in an unusual location: an allograft kidney artery.

Novel Imaging-Based Biomarkers for Identifying Carotid Plaque Vulnerability

Carotid artery disease has traditionally been assessed based on the degree of luminal narrowing. However, this approach, which solely relies on carotid stenosis, is currently being questioned with regard to modern risk stratification approaches. Recent guidelines have introduced the concept of the "vulnerable plaque," emphasizing specific features such as thin fibrous caps, large lipid cores, intraplaque hemorrhage, plaque rupture, macrophage infiltration, and neovascularization. In this context, imaging-based biomarkers have emerged as valuable tools for identifying higher-risk patients. Non-invasive imaging modalities and intravascular techniques, including ultrasound, computed tomography, magnetic resonance imaging, intravascular ultrasound, optical coherence tomography, and near-infrared spectroscopy, have played pivotal roles in characterizing and detecting unstable carotid plaques. The aim of this review is to provide an overview of the evolving understanding of carotid artery disease and highlight the significance of imaging techniques in assessing plaque vulnerability and informing clinical decision-making.

Cerebral embolisation during transcatheter edge-to-edge repair of the mitral valve with the MitraClip system: a prospective, observational study

BACKGROUND

New ischaemic brain lesions on magnetic resonance imaging (MRI) are reported in up to 86% of patients after transcatheter edge-to-edge repair of the mitral valve (TEER-MV). Knowledge of the exact procedural step(s) that carry the highest risk for cerebral embolisation may help to further improve the procedure.

AIMS

The aim of this study was to identify the procedural step(s) that are associated with an increased risk of cerebral embolisation during TEER-MV with the MitraClip system. Furthermore, the risk of overt stroke and silent brain ischaemia after TEER-MV was assessed.

METHODS

In this prospective, pre-specified observational study, all patients underwent continuous transcranial Doppler examination during TEER-MV to detect microembolic signals (MES). MES were assigned to specific procedural steps: (1) transseptal puncture and placement of the guide, (2) advancing and adjustment of the clip in the left atrium, (3) device interaction with the MV, and (4) removal of the clip delivery system and the guide. Neurological examination using the National Institutes of Health Stroke Scale (NIHSS) and cerebral MRI were performed before and after TEER-MV.

RESULTS

Fifty-four patients were included. The number of MES differed significantly between the procedural steps with the highest numbers observed during device interaction with the MV. Mild neurological deterioration (NIHSS ≤3) occurred in 9/54 patients. New ischaemic lesions were detected in 21/24 patients who underwent MRI. Larger infarct volume was significantly associated with neurological deterioration.

CONCLUSIONS

Cerebral embolisation is immanent to TEER-MV and predominantly occurs during device interaction with the MV. Improvements to the procedure may focus on this procedural step.

Sonografisches Neuromonitoring auf der Stroke Unit und in der neurologischen Intensivmedizin

Hintergrund Der Artikel gibt einen Überblick über die aktuellen diagnostischen Einsatzmöglichkeiten sonographischer Anwendung in der neurologischen Intensivmedizin.

Methoden Selektive Literaturrecherche mit kritischer Beurteilung ab dem Jahr 1984 sowie nationaler und internationaler Leitlinien sowie Expertenmeinung.

Ergebnisse Neben der raschen validen Abklärung akuter Schlaganfälle bieten verschiedene neurosonografische Monitoring-verfahren gerade in der Intensivmedizin spezifische Vorteile wie die beliebig häufige Wiederholbarkeit am Patientenbett selbst und die Darstellung in Echtzeit. Innovative Entwicklungen machen die Neurosonografie auch wissenschaftlich zu einem interessanten Gebiet.

Schlussfolgerung Die neurosonografische Diagnostik nimmt seit Jahren einen wichtigen Stellenwert in der neurologischen Intensivmedizin ein. Weitere Anstrengungen sind notwendig, um die Verbreitung der Methode zu fördern und durch wissenschaftliche Evidenz zu stärken.

Simultaneous assessment of plaque morphology, cerebral micro-embolic signal status and platelet biomarkers in patients with recently symptomatic and asymptomatic carotid stenosis

The relationship between plaque morphology, cerebral micro-embolic signals (MES) and platelet biomarkers in carotid stenosis patients warrants investigation.We combined data from two prospective, observational studies to assess carotid plaque morphology and relationship with cerebral MES and platelet biomarkers in patients with recently symptomatic (≤4 weeks of transient ischaemic attack (TIA)/ischaemic stroke) versus asymptomatic carotid stenosis. Plaque morphology on ultrasound was graded with Grey-Scale Median (GSM) and Gray-Weale (GW) scoring. Bilateral transcranial Doppler ultrasound classified patients as 'MES+ve' or 'MES-ve'. Full blood counts were analysed and flow cytometry quantified CD62P and CD63 expression, leucocyte-platelet complexes and reticulated platelets.Data from 42 recently symptomatic carotid stenosis patients were compared with those from 36 asymptomatic patients. There were no differences in median GSM scores between symptomatic and asymptomatic patients (25 vs. 30; P = 0.31) or between MES+ve vs. MES-ve symptomatic patients (36 vs. 25; P = 0.09). Symptomatic patients with GSM-echodense plaques (GSM ≥25) had higher platelet counts (228 vs. 191 × 10⁹/L), neutrophil-platelet (3.3 vs. 2.7%), monocyte-platelet (6.3 vs. 4.55%) and lymphocyte-platelet complexes (2.91 vs. 2.53%) than 'asymptomatic patients with GSM-echodense plaques' (P ≤ 0.03).Recently, symptomatic carotid stenosis patients with 'GSM-echodense plaques' have enhanced platelet production/secretion/activation compared with their asymptomatic counterparts. Simultaneous assessment with neurovascular imaging and platelet biomarkers may aid risk-stratification in carotid stenosis.

Transcranial Doppler ultrasonography in neurological surgery and neurocritical care

Transcranial Doppler (TCD) ultrasonography is an inexpensive, noninvasive means of measuring blood flow within the arteries of the brain. In this review, the authors outline the technology underlying TCD ultrasonography and describe its uses in patients with neurosurgical diseases. One of the most common uses of TCD ultrasonography is monitoring for vasospasm following subarachnoid hemorrhage. In this setting, elevated blood flow velocities serve as a proxy for vasospasm and can herald the onset of ischemia. TCD ultrasonography is also useful in the evaluation and management of occlusive cerebrovascular disease. Monitoring for microembolic signals enables stratification of stroke risk due to carotid stenosis and can also be used to clarify stroke etiology. TCD ultrasonography can identify patients with exhausted cerebrovascular reserve, and after extracranial-intracranial bypass procedures it can be used to assess adequacy of flow through the graft. Finally, assessment of cerebral autoregulation can be performed using TCD ultrasonography, providing data important to the management of patients with severe traumatic brain injury. As the clinical applications of TCD ultrasonography have expanded over time, so has their importance in the management of neurosurgical patients. Familiarity with this diagnostic tool is crucial for the modern neurological surgeon.

Clinical Role of Microembolic Signals in Adult Moyamoya Disease With Ischemic Stroke

Background and Purpose- Hemodynamic compromise has been implicated in moyamoya disease (MMD) with transient ischemic attacks or ischemic stroke. However, increasing evidence supports the notion that artery-to-artery embolism may also contribute to ischemic events based on microembolic signal (MES) monitoring. Methods- A total of 48 patients aged between 20 and 60 years with newly diagnosed MMD were enrolled and angiographically classified according to the Suzuki staging system. For detection of MESs, transcranial Doppler was performed at the middle cerebral artery bilaterally for a 30-minute period. Mean flow velocities in the middle cerebral artery were also evaluated and categorized into low (<40 cm/s), normal (40-80 cm/s), and high (>80 cm/s). Clinical characteristics, cerebral angiography findings, recent ischemic events within 3 months, and antiplatelet medication were correlated with transcranial Doppler findings. Results- MESs were detected in 11 of the 48 patients (23%), with a frequency of 11 of 89 (12%) examined hemispheres. The mean number of MESs was 2 (range, 1-6). Six of the 11 hemispheres (55%) presented with ischemic strokes or transient ischemic attacks, and 2 (18%) presented with hemorrhagic strokes. The presence of MESs was associated with recent ischemic events ( P=0.024) and high mean flow velocities ( P=0.016), which was usually observed in Suzuki stage I and II (early-stage MMD). After controlling for age, sex, and antiplatelet medication, both recent ischemic events (odds ratio, 6.294; 95% CI, 1.345-29.457; P=0.019) and high mean flow velocities (odds ratio, 6.172; 95% CI, 1.235-31.25; P=0.027) were found to be independent predictors of MESs. Conclusions- MESs were observed in patients with high mean flow velocities, particularly early-stage MMD, and clinically associated with recent ischemic events. A randomized controlled study is necessary to determine the efficacy of antiplatelet agents in the treatment of MES-positive MMD.

Cryptogenic stroke

The paper considers the epidemiology and general etiological characteristics of cryptogenic stroke (CS). It discusses the concept of embolic stroke with an unknown source of embolism. It also characterizes the most significant causes of CS, such as paroxysmal atrial fibrillation, atrial cardiopathy, aortic atheroma, non-stenotic cerebral atherosclerotic plaques, and malignant neoplasms. The paper describes approaches to the diagnosis and secondary prevention of CS and proposes etiological and neuroimaging diagnostic algorithms for CI. Clinical cases are also presented.

Microemboli After Successful Thrombectomy Do Not Affect Outcome but Predict New Embolic Events

Background and Purpose- We aimed to determine if microemboli after endovascular thrombectomy correlate with unfavorable outcomes despite successful recanalization. Methods- This is a prospective multicenter study of consecutive patients with ischemic stroke and occlusion of anterior circulation vessels (terminal internal carotid or main trunk of the middle cerebral artery/first-order branch of the main trunk of the middle cerebral artery segments of middle cerebral artery) after successful thrombectomy (modified Treatment In Cerebral Ischemia grades 2b-3). Microembolic signals (MES) were assessed by 30 minutes of transcranial Doppler monitoring within 72 hours of the last-seen-well time. Major outcomes included modified Rankin Scale at 90 days and infarct volume on head computed tomography at 24 hours. We also assessed early outcomes based on National Institutes of Health Stroke Scale variation and recurrence of stroke, transient ischemic attack, or systemic embolism within 90 days. Results- Among 111 patients, MES were detected in 43 (39%), with a median rate of 4 counts/h (interquartile range 2-12). The occurrence of MES was not associated with a significant difference in modified Rankin Scale (ordinal shift analysis, adjusted odds ratio, 1.06 [95% CI, 0.48-2.34] P=0.85) nor in functional independence (modified Rankin Scale, 0-2: adjusted odds ratio, 0.52 [95% CI, 0.19-1.39] P=0.19). Patients with and without MES had similar infarct volumes (adjusted beta, 11.2 [95% CI, -46.6 to +22.9] P=0.51) on 24-hour computed tomography. MES did predict new embolic events (adjusted Cox hazard ratio, 6.78 [95% CI, 1.63-27.8] P=0.01). Conclusions- MES detected by transcranial Doppler following endovascular treatment of anterior circulation occlusions do not predict clinical or radiological outcome. However, such emboli are an independent marker of recurrent embolic events within 90 days.

[Contrast-enhanced ultrasonography as the most perspective diagnostic method for unstable atherosclerotic plaque of carotid artery]

Problem of internal carotid artery disease diagnosis appears to be crucial today. Complications of this pathology are strokes and transient ischemic attacks. There is no technology for their prediction or at least stratifying risks. Some recent researches are devoted to a new diagnostic method. This new technology is called Contrast Enhanced Ultrasonography (CEUS) and followed by outstanding results in studying the morphological peculiarities of internal carotid artery plaques and predicting the probability of complications. CEUS is a new way for atherosclerotic process analysis because it is able to detect intraplaque neovascularization and vascular wall inflammation.

Reproducibility of Transcranial Doppler ultrasound in the middle cerebral artery

BACKGROUND

Transcranial Doppler ultrasound remains the only imaging modality that is capable of real-time measurements of blood flow velocity and microembolic signals in the cerebral circulation. We here assessed the repeatability and reproducibility of transcranial Doppler ultrasound in healthy volunteers and patients with symptomatic carotid artery stenosis.

METHODS

Between March and August 2017, we recruited 20 healthy volunteers and 20 patients with symptomatic carotid artery stenosis. In a quiet temperature-controlled room, two 1-h transcranial Doppler measurements of blood flow velocities and microembolic signals were performed sequentially on the same day (within-day repeatability) and a third 7-14 days later (between-day reproducibility). Levels of agreement were assessed by interclass correlation co-efficient.

RESULTS

In healthy volunteers (31±9 years, 11 male), within-day repeatability of Doppler measurements were 0.880 (95% CI 0.726-0.950) for peak velocity, 0.867 (95% CI 0.700-0.945) for mean velocity, and 0.887 (95% CI 0.741-0.953) for end-diastolic velocity. Between-day reproducibility was similar but lower: 0.777 (95% CI 0.526-0.905), 0.795 (95% CI 0.558-0.913), and 0.674 (95% CI 0.349-0.856) respectively. In patients (72±11 years, 11 male), within-day repeatability of Doppler measurements were higher: 0.926 (95% CI 0.826-0.970) for peak velocity, 0.922 (95% CI 0.817-0.968) for mean velocity, and 0.868 (95% CI 0.701-0.945) for end-diastolic velocity. Similarly, between-day reproducibility revealed lower values: 0.800 (95% CI 0.567-0.915), 0.786 (95% CI 0.542-0.909), and 0.778 (95% CI 0.527-0.905) respectively. In both cohorts, the intra-observer Bland Altman analysis demonstrated acceptable mean measurement differences and limits of agreement between series of middle cerebral artery velocity measurements with very few outliers. In patients, the carotid stenoses were 30-40% (n = 9), 40-50% (n = 6), 50-70% (n = 3) and > 70% (n = 2). No spontaneous embolisation was detected in either of the groups.

CONCLUSIONS

Transcranial Doppler generates reproducible data regarding the middle cerebral artery velocities. However, larger studies are needed to validate its clinical applicability.

TRIAL REGISTRATION

ClinicalTrial.gov (ID NCT 03050567), retrospectively registered on 15/05/2017.

Clinical Impact of the Microembolic Signal Burden During Catheter Ablation for Atrial Fibrillation: Just a Lot of Noise?

OBJECTIVES

Microembolic signal detection by transcranial Doppler ultrasonography may be considered a surrogate for cerebral events during invasive cardiac procedures. However, the impact of the microembolic signal count during pulmonary vein isolation on the clinical outcome is not well evaluated. We investigated the effect of the microembolic signal count on the occurrence of new silent cerebral embolism measured by diffusion-weighted imaging (DWI)-magnetic resonance imaging (MRI), changes in neuropsychological testing, and the occurrence of clinical events during long-term follow-up after pulmonary vein isolation.

METHODS

Pulmonary vein isolation was performed in 41 patients. The total microembolic signal burden (classified into "solid," "gaseous," and "equivocal") and sustained thromboembolic showers of greater than 30 seconds were recorded. Diffusion-weighted imaging-MRI and neuropsychological testing were performed before and after pulmonary vein isolation to assess for silent cerebral embolism and neuropsychological sequelae. Long-term follow-up was performed by telephone to assess for stroke/transient ischemic attack.

RESULTS

A total of 68,729 microembolic signals (14,893 solid, 11,909 gaseous, and 41,927 equivocal) with an average of 1676 signals per patient and 42 thromboembolic showers were recorded. No correlation between the microembolic signal/thromboembolic shower count and the occurrence of new DWI lesions or neuropsychological capability was found. After a mean follow-up ± SD of 49 ± 4 months, 1 patient had an overt transient ischemic event, which was not associated with a high microembolic signal count.

CONCLUSIONS

In this multicenter study, we found no impact of the intraprocedural microembolic symbol/thromboembolic shower count on the occurrence of new DWI lesions, neuropsychological capability, or overt neurologic deficits after pulmonary vein isolation. Thus, not only the microembolic signal count but also procedural/individual factors may contribute to commensurable clinical damage, which may challenge this method as a valid biomarker during pulmonary vein isolation.

Microembolic Signals Predict Recurrence of Ischemic Events in Symptomatic Patients with Middle Cerebral Artery Stenosis

Middle cerebral artery (MCA) stenosis is a common cause of ischemic stroke in Asian populations. We sought to determine whether microembolic signals (MESs) can predict the occurrence or recurrence of ischemia in symptomatic and asymptomatic patients with MCA stenosis. The symptomatic group had a significantly higher incidence of MES (30% vs. 16.2%, p < 0.05), as well as higher incidences of cerebral infarction and transient ischemic attack (TIA) (infarction, 13.0% vs. 4.4%, OR 3.123 [95% CI, 1.049-9.294], p < 0.05; TIA, 21.0% vs. 2.9%, OR = 7.108 [95% CI, 1.808-27.949], p < 0.001) than the asymptomatic group. After a follow-up period of 0.5-4.5 y, the subgroup of MES-positive (MES+) symptomatic patients had a significantly higher incidence of TIA (36.7% vs. 14.3%, OR = 1.623 [95% CI, 1.166-2.258]; p < 0.001) than the subgroup of MES-negative (MES-) symptomatic patients. The likelihood of the early occurrence of an endpoint event was also higher in the subgroup of MES+ symptomatic patients. In the group of asymptomatic patients with MCA stenosis, no significant differences were identified between the MES+ and MES- subgroups.

Internal Carotid Artery Occlusion: Pathophysiology, Diagnosis, and Management

PURPOSE OF REVIEW

Acute internal carotid artery occlusion (ICAO) is associated with large infarcts and poor clinical outcomes and contributes to morbidity and mortality worldwide. In this review, we discuss various etiologies and pathophysiology of clinical presentations of ICAO, different radiographic patterns, and management of patients with ICAO.

RECENT FINDINGS

Recanalization rates remain suboptimal with systemic thrombolysis amongst patients with acute ICAO. Recent success of endovascular therapy for vessel occlusion in anterior circulation has expanded the horizons; however, few patients with cervical dissections and ICAO were included in these landmark trials. Acute ICAO responds poorly to intravenous thrombolysis and portends worse clinical outcomes. Extracranial and intracranial ICAOs have varied clinical course and imaging patterns, with discrete cervical ICAO usually associated with better clinical outcomes while tandem occlusions predispose poor outcomes. Diagnostic catheter-based angiogram is often required since appearances of ICAO using non-invasive neuroimaging modalities are often deceiving. Repeated vascular imaging in acute to subacute phase to determine recanalization of ICAO is critical for secondary prevention. Recent success of endovascular procedures will continue to expand the horizons to improve the management of ICAO.

Statin Pretreatment and Microembolic Signals in Large Artery Atherosclerosis

OBJECTIVE

Although statin pretreatment (SP) is associated with better outcomes in patients with acute cerebral ischemia after an ischemic stroke/transient ischemic attack, data on the underlying mechanism of this beneficial effect are limited.

APPROACH AND RESULTS

We sought to evaluate the potential association between SP and microembolic signal (MES) burden in acute cerebral ischemia because of large artery atherosclerosis (LAA). We prospectively evaluated consecutive patients with first-ever acute cerebral ischemia because of LAA in 3 tertiary stroke centers over a 2-year period. All patients underwent continuous 1-hour transcranial Doppler monitoring of the relevant vessel at baseline (≤24 hours). SP was recorded and dichotomized as high dose or low-to-moderate dose. SP was documented in 43 (41%) of 106 LAA patients (mean age, 65.4±10.3 years; 72% men; low-to-moderate dose, 32%; high dose, 8%). There was a significant (P=0.022) dose-dependent effect between SP and MES prevalence: no SP (37%), SP with low-to-moderate dose (18%), and SP with high dose (0%). Similarly, a significant (P=0.045) dose-dependent effect was documented between SP and MES burden: no SP (1.1±1.8), SP with low-to-moderate dose (0.7±1.6), and SP with high dose (0±0). In multivariable logistic regression analysis adjusting for demographics, vascular risk factors, location of LAA, stroke severity, and other prevention therapies, SP was associated with lower likelihood of MES presence (odds ratio, 0.29; 95% confidence interval, 0.09-0.92; P=0.036). In addition, SP was found also to be independently related to higher odds of functional improvement (common odds ratio, 3.33; 95% confidence interval, 1.07-10.0; P=0.037).

CONCLUSIONS

We found that SP in patients with acute LAA is related with reduced MES presence and lower MES burden with an apparently dose-dependent association.

Online Measurement of Microembolic Signal Burden by Transcranial Doppler during Catheter Ablation for Atrial Fibrillation-Results of a Multicenter Trial

INTRODUCTION

Left atrial pulmonary vein isolation (PVI) is an accepted treatment option for patients with symptomatic atrial fibrillation (AF). This procedure can be complicated by stroke or silent cerebral embolism. Online measurement of microembolic signals (MESs) by transcranial Doppler (TCD) may be useful for characterizing thromboembolic burden during PVI. In this prospective multicenter trial, we investigated the burden, characteristics, and composition of MES during left atrial catheter ablation using a variety of catheter technologies.

MATERIALS AND METHODS

PVI was performed in a total of 42 patients using the circular-shaped multielectrode pulmonary vein ablation catheter (PVAC) technology in 23, an irrigated radiofrequency (IRF) in 14, and the cryoballoon (CB) technology in 5 patients. TCD was used to detect the total MES burden and sustained thromboembolic showers (TESs) of >30 s. During TES, the site of ablation within the left atrium was registered. MES composition was classified manually into "solid," "gaseous," or "equivocal" by off-line expert assessment.

RESULTS

The total MES burden was higher when using IRF compared to CB (2,336 ± 1,654 vs. 593 ± 231; p = 0.007) and showed a tendency toward a higher burden when using IRF compared to PVAC (2,336 ± 1,654 vs. 1,685 ± 2,255; p = 0.08). TES occurred more often when using PVAC compared to IRF (1.5 ± 2 vs. 0.4 ± 1.3; p = 0.04) and most frequently when ablation was performed close to the left superior pulmonary vein (LSPV). Of the MES, 17.004 (23%) were characterized as definitely solid, 13.204 (18%) as clearly gaseous, and 44.366 (59%) as equivocal.

DISCUSSION

We investigated the burden and characteristics of MES during left atrial catheter ablation for AF. All ablation techniques applied in this study generated a relevant number of MES. There was a significant difference in total MES burden using IRF compared to CB and a tendency toward a higher burden using IRF compared to PVAC. The highest TES burden was found in the PVAC group, particularly during ablation close to the LSPV. The composition of thromboembolic particles was balanced. The impact of MES, TES, and composition of thromboembolic particles on neurological outcome needs to be evaluated further. (Clinical Trial Registration: Deutsches Register Klinischer Studien, https://drks-neu.uniklinik-freiburg.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00003465. DRKS00003465.).

Advanced imaging in acute ischemic stroke

The evaluation and management of acute ischemic stroke has primarily relied on the use of conventional CT and MRI techniques as well as lumen imaging sequences such as CT angiography (CTA) and MR angiography (MRA). Several newer or less-established imaging modalities, including vessel wall MRI, transcranial Doppler ultrasonography, and 4D CTA and MRA, are being developed to complement conventional CT and MRI techniques. Vessel wall MRI provides high-resolution analysis of both extracranial and intracranial vasculature to help identify previously occult lesions or characteristics of lesions that may portend a worse natural history. Transcranial Doppler ultrasonography can be used in the acute setting as a minimally invasive way of identifying large vessel occlusions or monitoring the response to stroke treatment. It can also be used to assist in the workup for cryptogenic stroke or to diagnose a patent foramen ovale. Four-dimensional CTA and MRA provide a less invasive alternative to digital subtraction angiography to determine the extent of the clot burden and the degree of collateral blood flow in large vessel occlusions. Along with technological advances, these new imaging modalities are improving the diagnosis, workup, and management of acute ischemic stroke— roles that will continue to expand in the future.

Transcranial Doppler ultrasound in children with stroke and cerebrovascular disorders

PURPOSE OF REVIEW

A major advantage of transcranial Doppler (TCD) ultrasound is its ability to measure cerebral hemodynamics noninvasively at the patient's bedside. This article summarizes the basic physics and variables used during TCD, recent pediatric data published on the use of TCD in stroke and cerebrovascular disorders and how it may impact diagnosis and management, and some issues to be resolved so that TCD can be put into clinical practice.

RECENT FINDINGS

In sickle cell disease in children, TCD is the gold standard stroke prediction tool. Recent data suggest that TCD may provide important information in ischemic stroke because of other childhood arteriopathies such as moyamoya syndrome, transient or focal cerebral arteriopathy, and genetic/syndromic causes. TCD may also detect cerebral emboli and diagnose right-to-left atrial cardiac shunts in children with cryptogenic stroke and transient ischemic attack.

SUMMARY

There are many potential clinical applications for TCD in pediatric stroke and cerebrovascular disorders. Additional research in children is needed to determine whether TCD can identify markers of increased stroke risk, elucidate underlying stroke mechanisms, influence the choice of additional testing and treatment, and ultimately impact patient outcomes.

Contemporary carotid imaging: from degree of stenosis to plaque vulnerability

Carotid artery stenosis is a well-established risk factor of ischemic stroke, contributing to up to 10%-20% of strokes or transient ischemic attacks. Many clinical trials over the last 20 years have used measurements of carotid artery stenosis as a means to risk stratify patients. However, with improvements in vascular imaging techniques such as CT angiography and MR angiography, ultrasonography, and PET/CT, it is now possible to risk stratify patients, not just on the degree of carotid artery stenosis but also on how vulnerable the plaque is to rupture, resulting in ischemic stroke. These imaging techniques are ushering in an emerging paradigm shift that allows for risk stratifications based on the presence of imaging features such as intraplaque hemorrhage (IPH), plaque ulceration, plaque neovascularity, fibrous cap thickness, and presence of a lipid-rich necrotic core (LRNC). It is important for the neurosurgeon to be aware of these new imaging techniques that allow for improved patient risk stratification and outcomes. For example, a patient with a low-grade stenosis but an ulcerated plaque may benefit more from a revascularization procedure than a patient with a stable 70% asymptomatic stenosis with a thick fibrous cap. This review summarizes the current state-of-the-art advances in carotid plaque imaging. Currently, MRI is the gold standard in carotid plaque imaging, with its high resolution and high sensitivity for identifying IPH, ulceration, LRNC, and inflammation. However, MRI is limited due to time constraints. CT also allows for high-resolution imaging and can accurately detect ulceration and calcification, but cannot reliably differentiate LRNC from IPH. PET/CT is an effective technique to identify active inflammation within the plaque, but it does not allow for assessment of anatomy, ulceration, IPH, or LRNC. Ultrasonography, with the aid of contrast enhancement, is a cost-effective technique to assess plaque morphology and characteristics, but it is limited in sensitivity and specificity for detecting LRNC, plaque hemorrhage, and ulceration compared with MRI. Also summarized is how these advanced imaging techniques are being used in clinical practice to risk stratify patients with low- and high-grade carotid artery stenosis. For example, identification of IPH on MRI in patients with low-grade carotid artery stenosis is a risk factor for failure of medical therapy, and studies have shown that such patients may fair better with carotid endarterectomy (CEA). MR plaque imaging has also been found to be useful in identifying revascularization candidates who would be better candidates for CEA than carotid artery stenting (CAS), as high intraplaque signal on time of flight imaging is associated with vulnerable plaque and increased rates of adverse events in patients undergoing CAS but not CEA.

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.

18FDG-PET-CT: an imaging biomarker of high-risk carotid plaques. Correlation to symptoms and microembolic signals

BACKGROUND AND PURPOSE

We investigated whether uptake of (18)fluoro-2-deoxy-d-glucose (18FDG) positron emission tomography-computed tomography (PET-CT) correlated to clinical symptoms and presence of microembolic signals (MES) detected by transcranial Doppler in patients with carotid stenosis.

METHODS

18FDG-PET-CT and MES detection was performed in consecutive patients with 50% to 99% symptomatic or asymptomatic carotid stenoses. Uptake index was defined by a target to background ratio (TBR) between maximum standardized uptake value of the carotid plaque and the mean standardized uptake value of the jugular veins. End points for analysis were presence of symptoms and presence of MES.

RESULTS

We included 123 stenosis derived from 110 patients, 60 symptomatic and 63 asymptomatic. MES positive (+) lesions were found in 16%. TBR values were higher in symptomatic compared with asymptomatic (median 2.07 versus 1.78; P<0.0018) and in MES+ compared with MES- plaques (median 2.14 versus 1.86; P<0.008). TBR values were also higher in asymptomatic MES+ compared with MES- plaques (median 1.97 versus 1.76; P<0.03). The best TBR threshold value for symptomatic versus asymptomatic, for MES+ versus MES-, for symptomatic MES+ versus symptomatic or asymptomatic MES-, and for asymptomatic MES+ versus asymptomatic MES- plaques was 1.9. Sensitivity/specificity were, respectively, 56/77%, 73/63%, 79/64%, and 80/77%. We found a strong correlation between number of MES and TBR values (ρ 0.26; P=0.0043).

CONCLUSIONS

18FDG-PET-CT accurately detected high-risk carotid plaques. Also given its strong correlation to MES, 18FDG-PET-CT may be a useful tool in clinical practice.

Microembolic signals predict cerebral ischaemic events in patients with moyamoya disease

BACKGROUND AND PURPOSE

Recent studies found that microembolic signals (MESs) could be detected by transcranial Doppler in patients with moyamoya disease. However, the clinical significance of MESs in moyamoya disease remains unclear. Our aim was to investigate whether the MESs could predict cerebral ischaemic events in patients with moyamoya disease.

METHODS

Fifty-four consecutive patients with moyamoya disease were recruited. MESs were monitored by transcranial Doppler for 30 min in the bilateral middle cerebral arteries of each patient on admission. Patients were followed up for 1 year. The primary end-point was cerebral ischaemic events including stroke and transient ischaemic attack (TIA).

RESULTS

MESs were detected in 11 (20.4%) patients, with a frequency of 11 (10.2%) in 108 hemispheres. Logistic regression analysis revealed that previous ischaemic events within 3 months were associated with the presence of MESs (odds ratio 4.41, 95% CI 1.11-17.59). During a median follow-up of 384 days, 14 (13.0%) hemispheres had ischaemic events (seven strokes and seven TIAs). Cox regression showed that the hazard ratio for the risk of new ischaemic stroke and TIA in the hemispheres with MESs was 6.84 (95% CI 1.82-25.66) compared with those without, and 10.61 (95% CI 1.66-67.70) for ischaemic stroke alone, after controlling for age, sex, presence of ischaemic events at baseline, Suzuki stages and revascularization surgery.

CONCLUSIONS

In patients with moyamoya disease, the presence of MESs is associated with recent ischaemic symptoms and independently predicts cerebral ischaemic events. MES detection may be of potential clinical value in the management of patients with moyamoya disease.

Microembolic signals detected with transcranial doppler sonography differ between symptomatic and asymptomatic middle cerebral artery stenoses in Northeast China

Although microembolus monitoring has been widely used for ischemic cerebrovascular disease, the clinical significance of microembolic signal (MES) in asymptomatic middle cerebral artery (MCA) stenosis remains unclear. We aim to investigate the frequency of MES and the value of MES in predicting ischemic stroke secondary to asymptomatic MCA stenosis. From June 2011 to December 2012, microembolus monitoring was performed in 83 asymptomatic and 126 symptomatic subjects. By comparing the demographics and risk factors between the symptomatic and asymptomatic subjects, we found that the ratio of male sexuality and smoking history differed (101/126 vs 43/83, and 88/126 vs 38/83, respectively, p<0.01). The frequency of MES was significantly higher in the symptomatic group than in the asymptomatic group (49/126 vs 2/108, p<0.01). Specifically, the frequency of MES in the symptomatic and asymptomatic groups with mild stenosis, moderate stenosis, severe stenosis and occlusion groups was 4/18 (22.22%) vs 0/30 (0), 13/31 (41.94%) vs 1/28 (3.57%), 30/62 (48.39%) vs 1/39 (2.56%), 2/15 (13.33%) vs 0/11 (0), respectively. Except for the occlusive group, the frequency of MES is correlated with stenosis degree and symptom. Two patients in the asymptomatic group were found positive for MES, and the MES number was 1 for both. During the one-year follow-up, neither of them developed ischemic stroke. In conclusion, MES detected with TCD differs between symptomatic and asymptomatic MCA stenoses. Due to the low frequency, the value of MES as a predictor of subsequent ischemic stroke in patients with asymptomatic MCA stenosis might be limited.

Advances in transcranial Doppler clinical applications

IMPORTANCE OF THE FIELD

Diagnostic neurosonology techniques including transcranial Doppler (TCD), transcranial color Doppler imaging (TCDI) and power motion-mode (PMD) TCD provide information about various aspects of cerebrovascular status such as microemboli detection, dynamic autoregulation and long-duration real-time monitoring of flow characteristics. Although most of the information provided cannot be obtained by any other imaging methodology, and is critical in clinical decision-making in the care of various neurovascular diseases, these modalities are widely underutilized. Increasing the familiarity to neurosonological techniques is of crucial importance.

AREAS COVERED IN THIS REVIEW

After briefly reviewing TCD, TCDI and PMD techniques, classical features are summarized and recent developments in the clinical neurosonology applications with specific interest in the neurovascular disorders.

WHAT THE READER WILL GAIN

Practical perspectives of ultrasound evaluation of intracranial arterial status in various neurovascular diseases including sickle cell vasculopathy and vasospasm are reviewed in detail. Pearls on the neurosonological monitoring of acute ischemic stroke and increased intracranial pressure increase is provided. Standards of cerebral microembolism detection, right to left shunts diagnosis and cerebral autoregulation assessment are discussed methodologically. Future perspectives of therapeutic neurosonology including sonothrombolysis, microbubble-ultrasound-mediated gene and drug delivery into the brain, and alteration of the brain-blood barrier permeability are summarized.

TAKE HOME MESSAGE

Suitable with future medicine, neurosonology brings imaging to the bedside, which enables the treating physician to monitor a given intervention in real time. A non-invasive neurosonology-guided treatment of various diseases could be possible in the near future. The first and foremost step in gaining mastery in this very fruitful field is beginning to use it.

[Detection of micro-embolic signals: a review of the literature]

BACKGROUND

The detection of micro-embolic signals (MES), by transcranial Doppler sonography might be useful for risk stratification in patients with symptomatic and asymptomatic carotid or cerebral artery stenosis, dissections, aortic atheroma, interventional procedures, and right to left cardiac shunts.

AIM

Review of the technique and clinical situations of MES detection.

METHODS

PubMed search from 1990 to 2012.

RESULTS

MES were found in 0,19, 48% versus 0,3, and 12% of patients with symptomatic and asymptomatic inferior than 30, 30 to 69, and 70 to 99% carotid stenosis, respectively. MES were related to the risk of recurrent stroke or transient ischemic attack (TIA). In the ACES study, the absolute annual risk of stroke or TIA after 2 years was 7% with vs 3% without MES. In patients with intracranial stenosis, the risk of stroke recurrence was 48% with vs 7% without MES at 13.6 months follow-up. MES were reported in 25% of the symptomatic versus none of the asymptomatic patients with intracranial stenosis.

CONCLUSION

Detection of MES is feasible and reproducible for multicenter studies, using rigourous methodology and long lasting recordings. It may contribute to risk stratification, especially in patients with extra- or intracranial stenosis.

Vascularization of carotid plaque in recently symptomatic patients is associated with the occurrence of transcranial microembolic signals

BACKGROUND AND PURPOSE

Microembolic signals (MES) are detectable in the middle cerebral artery by transcranial ultrasound downstream to atherosclerotic lesions of the internal carotid artery (ICA) in patients with stroke or transient ischaemic attack. The occurrence of MES predicts future risk of stroke in patients with symptomatic and asymptomatic carotid stenosis. The detection of intra-plaque neo-vascularization by contrast-enhanced ultrasound (CEUS) in atherosclerotic plaques of the ICA is associated with future cardiovascular/cerebrovascular events. We investigated whether there is an association between both surrogate markers of future vascular events.

METHODS

Forty-one patients with symptomatic atherosclerotic plaques underwent ipsilateral transcranial ultrasound MES detection for 30 min followed by a CEUS investigation of the plaque. The occurrence and number of MES was documented, and the degree of intra-plaque neo-vascularization was measured semi-quantitatively.

RESULTS

During the 30 min investigation, 17 patients had MES and nine of them showed neo-vascularization of the atherosclerotic plaque. The remaining 24 patients did not have MES, and only in four patients of this group could plaque neo-vascularization be demonstrated (P = 0.020).

CONCLUSIONS

We found an association between the occurrence of MES and the presence of neo-vascularization in patients with symptomatic atherosclerotic carotid plaque. Therefore, plaque neo-vascularization might also be a surrogate marker of future stroke risk.

A mechanistic investigation into non-infarcted brain injury induced by cerebral artery microemboli

To establish a rat brain injury by non-infarction process model induced by cerebral artery microemboli which would be used to further explore the neural injury mechanisms of cerebral artery microemboli. Seventy-two Sprague-Dawley rats were randomly divided into the microemboli group and the sham group; 100 25-50 μm microemboli in 300 μl or the same amount of saline were injected into the left carotid artery, respectively. The severity of neuron damage was assessed 3 and 7 days after the operation, using haematoxylin-eosin (HE) staining and immunohistochemical staining for caspase-3. Immunohistochemical staining for CD11b and GFAP were used to quantitatively analyse hyperplasia and the activation of microglia and astrocytes. TNF-α expression was detected by using ELISA and the NF-κB expression was detected by employing Western blotting. The results of HE staining had shown that ischaemic infarct foci were not detected in either the microemboli group or sham group. Only a few apoptotic cells and a few cells with the positive expression of CD11b and GFAP were detected in the sham group. And compared with that of the sham group, the number of apoptotic cells and the positive expression of CD11b and GFAP in the microemboli group were significantly increased (P < 0.001). These parameters were also significantly increased 7 days after the operation compared to rats 3 days after surgery (P < 0.001). The expressions of TNF-α and NF-κB were significantly increased in the microemboli group (P < 0.001), and the increase of the expression of TNF-α and NF-κB on the 3 days was more significant compared to that of TNF-α and NF-κB on 7 days (P < 0.001). Injection of 25-50 μm microemboli at a dose of 100 microemboli in 300 μl into the carotid artery of rats did not result in cerebral infarction, but led to neuronal apoptosis, hyperplasia and activation of microglia and astrocytes. This leads us to conclude that TNF-α and NF-κB may play important roles in the pathogenesis of neuronal apoptosis induced by microemboli in the cerebral arteries.

Diagnosis of and treatment for symptomatic carotid stenosis: an updated review

Carotid stenoses of ≥50% account for about 15-20% of strokes. Their degree may be moderate (50-69%) or severe (70-99%). Current diagnostic methods include ultrasound, MR- or CT-angiography. Stenosis severity, irregular plaque surface, and presence of microembolic signals detected by transcranial Doppler predict the early recurrence risk, which may be as high as 20%. Initial therapy comprises antiplatelets and statins. Benefit of revascularization is greater in men, in older patients, and in severe stenosis; patients with moderate stenoses may also profit particularly if the plaque has an irregular aspect. An intervention should be performed within <2 weeks. In large randomized studies comparing endarterectomy and stenting, endovascular therapy was associated with a higher risk of periprocedural stroke, yet in some studies, with a lower risk of myocardial infarction and of cranial neuropathy. These trials support endarterectomy as the first choice treatment. Risk factors for each of the two therapies have been indentified: coronary artery disease, neck radiation, contralateral laryngeal nerve palsy for endarterectomy, and, elderly patients (>70 years), arch vessel tortuosity and plaques with low echogenicity on ultrasound for carotid stenting. Lastly, in direct comparisons, a contralateral occlusion increases the risk of periprocedural complications in both types of treatment.

[Sonographic diagnostics in neurological emergency and intensive care medicine]

BACKGROUND

This article gives an up-to-date overview of neurosonographic emergency and intensive care diagnostics.

METHODS

Selective literature research from 1984 with critical appraisal and including national and international guidelines.

RESULTS

Fast and valid diagnostics in acute stroke is the main field of application of neurosonography. Specific monitoring methods bear great advantages for intensive care patients, especially "as-often-as-wanted" repetitive imaging under real-time conditions. A number of new developments make neurosonography an interesting area of research.

CONCLUSIONS

Neurosonography has played a key role in neurological emergency and intensive care medicine for many years. It remains important to continuously support dissemination of the method.

Microembolus detection by transcranial Doppler sonography: review of the literature

Transcranial Doppler can detect microembolic signals which are characterized by unidirectional high intensity increase, short duration, random occurrence, and a “whistling” sound. Microembolic signals have been detected in a number of clinical settings: carotid artery stenosis, aortic arch plaques, atrial fibrillation, myocardial infarction, prosthetic heart valves, patent foramen ovale, valvular stenosis, during invasive procedures (angiography, percutaneous transluminal angioplasty), surgery (carotid, cardiopulmonary bypass, orthopedic), and in certain systemic diseases. Microembolic signals are frequent in large artery disease, less commonly detected in cardioembolic stroke, and infrequent in lacunar stroke. This article provides an overview about the current state of technical and clinical aspects of microembolus detection.

Silent cerebral events in asymptomatic carotid stenosis

BACKGROUND

Approximately 20% of strokes are attributable to carotid stenosis. However, the number of asymptomatic patients needed to prevent one stroke or death with endarterectomy is high at 17 to 32. There is a clear need to identify asymptomatic individuals at high risk of developing future ischemic events to improve the cost-effectiveness of surgery. Our aim was to examine the evidence for subclinical microembolization and silent brain infarction in the prediction of stroke in asymptomatic carotid stenosis using transcranial Doppler (TCD), computed tomography (CT), and magnetic resonance imaging (MRI).

METHODS

The review was conducted according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Articles regarding humans between 1966 and 2010 were identified through systematic searches of Pubmed, MEDLINE, and EMBASE electronic databases using a predetermined search algorithm.

RESULTS

Fifty-eight full text articles met the inclusion criteria. A median of 28% of microemboli positive patients experienced a stroke or transient ischemic attack during follow-up compared with 2% of microemboli negative patients (P = .001). The same was true for the end point of stroke alone with a median of 10% of microemboli positive patients experiencing a stroke vs 1% of microemboli negative patients (P = .004). A specific pattern of silent CT infarctions was related to future stroke risk (odds ratio [OR] = 4.6; confidence interval [CI] = 3.0-7.2; P < .0001). There are no prospective MRI studies linking silent infarction and stroke risk.

CONCLUSIONS

There is level 1 evidence for the use of TCD to detect microembolization as a risk stratification tool. However, this technique requires further investigation as a stroke prevention tool and would be complemented by improvements in carotid plaque imaging.

Vascular imaging in stroke: comparative analysis

Advances in stroke treatment have mirrored advances in vascular imaging. Understanding and advances in reperfusion therapies were made possible by improvements in computed tomographic angiography, magnetic resonance angiography, neurovascular ultrasound, and renewed interest in catheter angiography. As technology allows better noninvasive vascular diagnosis, digital subtraction angiography (the remaining gold standard for vascular imaging) is increasingly used for rescue procedures and elective interventions. This review will examine specific advantages and disadvantages of different vascular imaging modalities as related to stroke diagnosis.

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.

Potential role of PMD-TCD monitoring in the management of hemodynamically unstable intracranial stenosis

A 54-year-old woman started to loose vision 2 days prior to admission and also experienced left-sided headache, nausea, emesis, and disorientation. Magnetic resonance imaging (MRI) revealed bilateral posterior cerebral artery and cerebellar infarctions. Transcranial power motion Doppler (PMD-TCD) showed blunted flow signal in the proximal basilar artery (BA) suggestive for a high-grade stenosis also seen on magnetic resonance angiography (MRA). Dual antiplatelet therapy with aspirin and clopidogrel was started. Catheter angiography confirmed the proximal high-grade BA stenosis. After angiography, the patient experienced hypertensive crisis with severe headache. Blood pressure was lowered and headache resolved. One hour later she developed fluctuating level of consciousness and motor symptoms. PMD-TCD findings were suggestive for an intraluminal thrombus that moved from the proximal to the distal basilar artery, presumably further contributing to brain stem hypoperfusion and neurological deterioration. To achieve a compromise between lower blood pressure and maintenance of brain perfusion, hypervolemic hemodilution with intravenous dextran-40 was initiated. Patient's symptoms resolved to baseline and MRI showed no new parenchymal lesions.

Microemboli-monitoring during the acute phase of ischemic stroke: is it worth the time?

Background

The prevalence of microembolic signals (MES) during the acute phase of ischemic stroke and its influence on outcome is not well studied. The aim of our study was to determine the prevalence of MES, the different factors that are associated with the presence of MES and the association between MES and outcomes in stroke patients investigated within 6 hours after the onset of ischemic stroke.

Methods

We included unselected ischemic stroke patients who underwent microemboli-monitoring within six hours after stroke onset. Microemboli-monitoring of both middle cerebral arteries (MCA) was done for a period of 1 hour using 2-MHz probes applied over the trans-temporal window. Prevalence of MES, predictors for the presence of MES and the association between MES and various outcome factors were analyzed.

Results

Forty patients were included. The mean age of the patients was 70 years. The prevalence of either ipsilateral or contralateral MES were 25% (n = 10). The predictors for the presence of MES were older age (OR 9; p = 0.03), higher NIHSS (OR 28; p = 0.02), intracranial stenosis (OR 10; p = 0.04) and embolic stroke (large-artery atherosclerosis and cardioembolism on TOAST classification) (OR 7; p = 0.06). MES were not independently associated with short-term functional outcome, long-term mortality or future vascular events.

Conclusions

MES are moderately frequent following acute ischemic stroke. Microemboli-monitoring helps to better classify the stroke etiology. However, the presence MES did not have any prognostic significance in this study.

Complex Plaques in the Proximal Descending Aorta

Background and Purpose— To investigate the incidence of retrograde flow from complex plaques (≥4-mm-thick, ulcerated, or superimposed thrombi) of the descending aorta (DAo) and its potential role in embolic stroke.

Methods— Ninety-four consecutive acute stroke patients with aortic plaques ≥3-mm-thick in transesophageal echocardiography were prospectively included. MRI was performed to localize complex plaques and to measure time-resolved 3-dimensional blood flow within the aorta. Three-dimensional visualization was used to evaluate if diastolic retrograde flow connected plaque location with the outlet of the left subclavian artery, left common carotid artery, or brachiocephalic trunk. Complex DAo plaques were considered an embolic source if retrograde flow reached a supra-aortic vessel that supplied the territory of visible acute and embolic retinal or cerebral infarction.

Results— Only decreasing heart rate was correlated (P <0.02) with increasing flow reversal to the aortic arch. Retrograde flow from complex DAo plaques reached the left subclavian artery in 55 (58.5%), the left common carotid artery in 23 (24.5%), and the brachiocephalic trunk in 13 patients (13.8%). Based on routine diagnostics and MRI of the ascending aorta/aortic arch, stroke etiology was determined in 57 and cryptogenic in 37 patients. Potential embolization from DAo plaques was then identified in 19 of 57 patients (33.3%) with determined and in 9 of 37 patients (24.3%) with cryptogenic stroke.

Conclusions— Retrograde flow from complex DAo plaques was frequent in both determined and cryptogenic stroke and could explain embolism to all brain territories. These findings suggest that complex DAo plaques should be considered a new source of stroke.

Carotid wall thickness and stroke risk in patients with asymptomatic internal carotid stenosis

OBJECTIVE

Aim of this study was to investigate if the risk of stroke and other vascular diseases can be predicted in subjects with severe asymptomatic carotid artery stenosis on the basis of carotid wall thickness evaluation.

METHODS

We included 162 consecutive subjects with asymptomatic internal carotid artery stenosis of 60% or greater reduction in diameter. Demographic characteristics, vascular risk factors, therapy, degree of carotid stenosis and carotid intima-media thickness (IMT) were detailed for all subjects. Subjects were prospectively evaluated for a median period of 35 months (min=10, max=47). Outcome measures were: the occurrence of ischemic stroke ipsilateral to carotid stenosis and any other vascular event.

RESULTS

Thirty subjects (18.5%) suffered a vascular event: 16 (53%) myocardial infarctions and 14 (47%) strokes. Older age and higher IMT values were the only factors significantly associated with the risk of vascular events. The hazard ratio (adjusted for age, sex and other risk factors) for each 0.1 mm of IMT increase resulted 1.30 (95% CI: 1.14, 1.18) for combined vascular events, 1.47 for cerebrovascular events (95% CI: 1.16, 1.87) and 1.24 (95% CI: 1.09, 1.42) for cardiovascular events. Values of IMT above 1.15 mm increased the risk of having a stroke 19 times and the risk of having a myocardial infarction two times.

CONCLUSIONS

An increased carotid wall thickness can be considered as a marker of an increased risk of vascular events in asymptomatic subjects with internal carotid artery stenosis>60%. Highest IMT values are able to identify subjects with specific stroke risk. This information could be of interest to recognize subjects who might benefit most from surgical or revascularization procedures.