Microembolic Signals Detected by Transcranial Doppler Predict Future Stroke and Poor Outcomes

Risk Factors and Clinical Significance of Ultra-Long-Term Microischemia After Intracranial Aneurysm Embolization

INTRODUCTION

This study aimed to explore influencing factors and clinical significance of ultra-long-term microischemia following intracranial aneurysm (IA) embolization and establish a theoretical foundation for reducing both the incidence of ultra-long-term microischemia and cognitive dysfunction in patients post embolization.

METHODS

A retrospective analysis was conducted on data from 147 patients who received endovascular treatment for IAs. Patients were categorized into microischemic and control (non-microischemic) groups on the based on the findings of high-resolution magnetic resonance vessel wall imaging (HR-VWI) examinations performed 3 days postoperatively and 6 months postoperatively. Risk factors for the occurrence of ultra-long-term microischemia were determined by univariate analysis and multivariate logistic regression analysis.

RESULTS

Out of 147 patients included in the study, 51 (34.69%) developed microischemia while the remaining 96 (65.31%) did not experience this condition. Analysis revealed that factors such as sex, age, history of underlying diseases (hypertension, diabetes mellitus), aneurysmal site characteristics, the presence or absence of stenosis in the aneurysm-bearing artery, modified Fisher score at admission, Barthel's index at discharge, immunoinflammatory index at 3 days postoperatively and at the 6-month follow-up, the presence or absence of aneurysmal wall enhancement, and the presence or absence of aneurysmal lumen showed no statistically significant differences between the two groups (all P > 0.05). By contrast, variables like in operative time, rupture status of the aneurysm before surgery according to World Federation of Neurologic Surgeons (WFNS) grade, aneurysm size, number of stents used, number of guidewires and catheters used, and Evans index between the two groups were found to have statistically significant disparities between those who developed microischemia and those who did not (P < 0.05). A subsequent multivariate analysis revealed that aneurysm size, Evans index, and the number of stents used were independent risk factors for the occurrence of ultra-long-term microischemia after surgical intervention of aneurysms (P < 0.05). The receiver operating characteristic (ROC) curves of the patients were constructed on the basis of risk factors determined through multivariate logistic regression analysis. Results indicated that aneurysm size (area under ROC curve (AUC) 0.619, sensitivity 94.7%, specificity 17.1%, P = 0.049), Evans index (AUC 0.670, sensitivity 96.4%, specificity 26.8%, P = 0.004), and number of stents (AUC 0.639, sensitivity 44.6%, specificity 90.2%, P < 0.001) effectively predicted the occurrence of microischemia. The incidence of cognitive dysfunction was higher in the microischemic group than in the control group (P < 0.05), and a greater number of microischemic foci was associated with a higher incidence of cognitive dysfunction. The proportion of microschemia foci in the thalamus and basal ganglia in patients with cognitive dysfunction (60.87%) was significantly higher than that in patients without cognitive dysfunction (34.55%) (P < 0.05).

CONCLUSION

Aneurysm size, Evans index > 0.3, and the quantity of stents were independent risk factors for the occurrence of ultra-long-term microischemia after aneurysm embolization and provided good predictive performance. Cognitive dysfunction was closely associated with microischemia, with its severity increasing with an increase in the number of ischemic foci.

Correlation of microembolism risk factors with age in the ischemic stroke recovery period

Identification of the age-related features of interaction between the risk factors of microembolism can improve understanding of the mechanisms underlying the development of ischemic stroke (IS). The study was aimed to assess the effects of age and other risk factors of stroke on the biophysical characteristics of microembolic signals (MES) recorded during the ischemic stroke recovery period. Transcranial Doppler ultrasound (TCD) involving microembolus detection (MED) was performed in 515 people, the data of 28 patients having a history of ischemic stroke, among them 9 women (32%) and 19 men (68%) aged 33–78 (average age 58 ± 13 years), were included in the study. Using the mixed-effects linear model it was found that age and interaction between age and atrial fibrillation affected the power of MES. The increase in the power of the recorded MES with age is observed, that is especially evident in patients with atrial fibrillation (р < 0.0005). As for cardioembolic IS variant, the power and duration of MES turn out to be significantly higher in elderly patients (p < 0.0005). The power of MES gradually increases with age in patients with no atherosclerosis and gradually decreases in patients with atherosclerosis, while MES power in patients with atherosclerosis in general (all age groups) is significantly higher (р < 0.0005) than that observed in patients with no atherosclerosis.

Application of transcranial Doppler in cerebrovascular diseases

Transcranial Doppler (TCD) is a rapid and non-invasive diagnostic technique that can provide real-time measurements of the relative changes in cerebral blood velocity (CBV). Therefore, TCD is a useful tool in the diagnosis and treatment of clinical cerebrovascular diseases (CVDs). In this review, the basic principles of TCD and its application in CVD were outlined. Specifically, TCD could be applied to evaluate occlusive CVD, assess collateral circulation in patients with ischemic stroke, and monitor cerebral vascular occlusion before and after thrombolysis as well as cerebral vasospasm (VSP) and microembolization signals after aneurysmal subarachnoid hemorrhage (SAH). Moreover, TCD could predict short-term stroke and transient cerebral ischemia in patients with anterior circulation occlusion treated with endovascular therapy and in patients with anterior circulation vascular occlusion. Additionally, TCD not only could monitor blood velocity signals during carotid endarterectomy (CEA) or carotid artery stenting (CAS) but also allowed earlier intervention through early recognition of sickle cell disease (SCD). Presently, TCD is a useful prognostic tool to guide the treatment of CVD. On the one hand, TCD is more commonly applied in clinical research, and on the other hand, TCD has an increasing role in the management of patients. Collectively, we review the principles and clinical application of TCD and propose some new research applications for TCD.

Infarction Patterns and Recurrent Adverse Cerebrovascular Events in Moyamoya Disease

For moyamoya disease (MMD) patients who suffered an acute ischemic attack, the infarction patterns on DWI and its association with recurrent adverse cerebrovascular events (ACEs) after bypass surgery remain unknown. 327 patients who suffered an acute ischemic attack and received following revascularization surgery were retrospectively reviewed and were divided into three patterns according to the lesion number and distribution on DWI that obtained within 7 days of onset: no acute infarction (NAI), single acute infarction (SAI), and multiple acute infarctions (MAIs). We used Cox proportional hazard models to estimate hazard ratios (HR) for associations of infarction patterns and the risk of recurrent ACEs and strokes. Over a median follow-up of 41 months (IQR 26-60), there were 61 ACEs and 27 strokes. Compared to the NAI cohort, patients with SAI (HR, 2.92; 95% CI, 1.41-6.05; p = 0.004) and MAIs (HR, 4.44; 95% CI, 2.10-9.41; p < 0.001) were associated with higher risk of ACEs recurrences. In analysis adjusted for age and surgery modalities, the corresponding HR was 2.90 (95% CI: 1.41-5.98) for SAI and 4.10 (95% CI: 1.95-8.63) for MAIs, and this effect remained persistent on further adjustment for several potential confounders. Similar but less precise association was found in separate analysis that only takes into account stroke recurrences. Thus, different infarction patterns on DWI imply different risks of recurrent ACEs, and more attention should be paid to prevent ACEs in MMD patients with MAIs.

Intracranial microembolic signals might be a potential risk factor for cognitive impairment

Objective: We aimed to explore the relationship between microembolic signals (MES) and cognitive impairment in patients with neurological disorders using a 30-minute MES monitoring test.Methods: We retrospectively reviewed patients who visited outpatient departments and underwent a 30-minute MES monitoring session using dual-channel transcranial doppler (TCD) at Beijing Tiantan hospital between July 2016 and December 2018. All patients completed the Montreal Cognitive Assessment (MoCA) and underwent magnetic resonance imaging (MRI). Cognitive impairment was defined as a MoCA score of less than 26. MES were identified according to the criteria of the International Consensus Group on Microembolus Detection.Results: Of the 1356 subjects who underwent MES monitoring, 159 patients (including 50 cases of MES positive and 109 cases of MES negative) had both analyzable MES monitoring recording and cognition evaluation data, of which 72 had cognitive impairment. Compared with the group with no deficits in cognitive function, the proportion of MES positive was significantly higher in patients with impaired cognitive function - that is, 47% (34/72) versus 18.4% (16/87), respectively, with p < 0.05. In multivariate logistic regression analysis, MES were independently associated with lower MoCA score (odd ratios (OR), 7.36; 95% confidence intervals (CI), 2.72-19.85, P < 0.0001).Conclusions: In this retrospective study, we found a possible correlation and relationship between MES and cognitive impairment. Further studies are required to determine whether continuous cerebral microembolization to the brain will lead to progressive cognitive impairment.