Imaging in Endovascular Stroke Trials

Single vs. Multiphase Computed Tomography angiography in acute internal carotid artery occlusion: An accuracy and interobserver agreement study

OBJECTIVE

Accurate differentiation between the intracranial and extracranial location of the acute internal carotid artery (ICA) occlusion is essential for guiding treatment decisions and mechanical thrombectomy planning. Multiphase Computed Tomography angiography (mCTA) appears to be superior to Single-phase Computed Tomography angiography (sCTA) in the evaluation of acute ICA occlusions. The main objective of our research is to study the accuracy of mCTA compared to sCTA in distinguishing isolated acute intracranial ICA occlusion from extracranial or tandem occlusion.

METHODS

Two observers independently analyzed sCTA and mCTA of patients with acute ICA occlusion at two different time points. The location of the occlusion was categorized as intracranial or extracranial for both imaging techniques and then compared with digital subtraction angiography (gold standard). Sensitivity and specificity rates for isolated intracranial ICA occlusion on sCTA and mCTA were calculated. Kappa statistics were used to assess interobserver agreement.

RESULTS

The sensitivity of sCTA and mCTA was 48.28% (28.36%-68.19%) and 79.31% (62.84%-95.78%) respectively for the diagnosis of isolated intracranial ICA occlusion, with an almost perfect interobserver agreement between both observers (p < 0.001).

CONCLUSIONS

Our research suggests that mCTA is more accurate than sCTA in distinguishing isolated intracranial occlusions from extracranial or tandem occlusions.

Cerebral Collateral Circulation in the Era of Reperfusion Therapies for Acute Ischemic Stroke

Clinical outcomes of patients with acute ischemic stroke depend in part on the extent of their collateral circulation. A good collateral circulation has also been associated with greater benefit of intravenous thrombolysis and endovascular treatment. Treatment decisions for these reperfusion therapies are increasingly guided by a combination of clinical and imaging parameters, particularly in later time windows. Computed tomography and magnetic resonance imaging enable a rapid assessment of both the collateral extent and cerebral perfusion. Yet, the role of the collateral circulation in clinical decision-making is currently limited and may be underappreciated due to the use of rather coarse and rater-dependent grading methods. In this review, we discuss determinants of the collateral circulation in patients with acute ischemic stroke, report on commonly used and emerging neuroimaging techniques for assessing the collateral circulation, and discuss the therapeutic and prognostic implications of the collateral circulation in relation to reperfusion therapies for acute ischemic stroke.

Reversed ophthalmic artery flow in patients with acute ischemic stroke and ipsilateral significant extracranial carotid artery stenosis, and its effect in functional outcome

Background

Cerebral hemodynamics and collateral circulation have an important role in determining stroke outcome, while the role of primary collateral is well known, the role of secondary collaterals including ophthalmic artery flow is still controversial. Our aim was to evaluate the flow of ophthalmic artery in patients with acute ischemic stroke and significant extracranial carotid stenosis and assess its role on the functional outcome. Thirty patients with acute ischemic stroke and extracranial carotid stenosis were included from Ain Shams University hospitals, color coded duplex was used to assess extracranial carotid arteries, ophthalmic artery was assessed by transcranial color-coded duplex. According to ophthalmic artery flow patients were divided into two groups, one with forward and other with reversed flow. Modified Rankin Scale (MRS) after 3 months was compared between the two groups

Results

Reversed ophthalmic artery flow (ROAF) was seen among 10 (33.33%) patients. After 3 month MRS was better in ROAF group (1.5 ± 1.958) than forward ophthalmic artery flow (FOAF) group (2.1 ± 1.954) but with no statistical difference (p value 0.398); furthermore, the difference between MRS after 3 months and discharge was significant in ROAF group (p value 0.042).

Conclusions

Transcranial duplex is a noninvasive, safe method in determining ophthalmic artery flow; furthermore, ROAF could help in better stroke outcome.

Evaluation of Artificial Intelligence-Powered Identification of Large-Vessel Occlusions in a Comprehensive Stroke Center

BACKGROUND AND PURPOSE

Artificial intelligence algorithms have the potential to become an important diagnostic tool to optimize stroke workflow. Viz LVO is a medical product leveraging a convolutional neural network designed to detect large-vessel occlusions on CTA scans and notify the treatment team within minutes via a dedicated mobile application. We aimed to evaluate the detection accuracy of the Viz LVO in real clinical practice at a comprehensive stroke center.

MATERIALS AND METHODS

Viz LVO was installed for this study in a comprehensive stroke center. All consecutive head and neck CTAs performed from January 2018 to March 2019 were scanned by the algorithm for detection of large-vessel occlusions. The system results were compared with the formal reports of senior neuroradiologists used as ground truth for the presence of a large-vessel occlusion.

RESULTS

A total of 1167 CTAs were included in the study. Of these, 404 were stroke protocols. Seventy-five (6.4%) patients had a large-vessel occlusion as ground truth; 61 were detected by the system. Sensitivity was 0.81, negative predictive value was 0.99, and accuracy was 0.94. In the stroke protocol subgroup, 72 (17.8%) of 404 patients had a large-vessel occlusion, with 59 identified by the system, showing a sensitivity of 0.82, negative predictive value of 0.96, and accuracy of 0.89.

CONCLUSIONS

Our experience evaluating Viz LVO shows that the system has the potential for early identification of patients with stroke with large-vessel occlusions, hopefully improving future management and stroke care.

Toward automated classification of pathological transcranial Doppler waveform morphology via spectral clustering

Cerebral Blood Flow Velocity waveforms acquired via Transcranial Doppler (TCD) can provide evidence for cerebrovascular occlusion and stenosis. Thrombolysis in Brain Ischemia (TIBI) flow grades are widely used for this purpose, but require subjective assessment by expert evaluators to be reliable. In this work we seek to determine whether TCD morphology can be objectively assessed using an unsupervised machine learning approach to waveform categorization. TCD beat waveforms were recorded at multiple depths from the Middle Cerebral Arteries of 106 subjects; 33 with Large Vessel Occlusion (LVO). From each waveform, three morphological features were extracted, quantifying onset of maximal velocity, systolic canopy length, and the number/prominence of peaks/troughs. Spectral clustering identified groups implicit in the resultant three-dimensional feature space, with gap statistic criteria establishing the optimal cluster number. We found that gap statistic disparity was maximized at four clusters, referred to as flow types I, II, III, and IV. Types I and II were primarily composed of control subject waveforms, whereas types III and IV derived mainly from LVO patients. Cluster morphologies for types I and IV aligned clearly with Normal and Blunted TIBI flows, respectively. Types II and III represented commonly observed flow-types not delineated by TIBI, which nonetheless deviate from normal and blunted flows. We conclude that important morphological variability exists beyond that currently quantified by TIBI in populations experiencing or at-risk for acute ischemic stroke, and posit that the observed flow-types provide the foundation for objective methods of real-time automated flow type classification.

Non-invasive sensor technology for prehospital stroke diagnosis: Current status and future directions

BACKGROUND

The diagnosis of stroke in the prehospital environment is the subject of intense interest and research. There are a number of non-invasive external brain monitoring devices in development that utilize various technologies to function as sensors for stroke and other neurological conditions. Future increased use of one or more of these devices could result in substantial changes in the current processes for stroke diagnosis and treatment, including transportation of stroke patients by emergency medical services.

AIMS

The present review will summarize information about 10 stroke sensor devices currently in development, utilizing various forms of technology, and all of which are external, non-invasive brain monitoring devices.

SUMMARY OF REVIEW

Ten devices are discussed including the technology utilized, the indications for use (stroke and, when relevant, other neurological conditions), the environment(s) indicated for use (with a focus on the prehospital setting), a description of the physical structure of each instrument, and, when available, findings that have been published in peer-reviewed journals or otherwise reported. The review is organized based on the technology utilized by each device, and seven distinct forms were identified: accelerometers, electroencephalography (EEG), microwaves, near-infrared, radiofrequency, transcranial doppler ultrasound, and volumetric impedance phase shift spectroscopy.

CONCLUSIONS

Non-invasive external brain monitoring devices are in various stages of development and have promise as stroke sensors in the prehospital setting. Some of the potential applications include to differentiate stroke from non-stroke, ischemic from hemorrhage stroke, and large vessel occlusion (LVO) from non-LVO ischemic stroke. Successful stroke diagnosis prior to hospital arrival could transform the current diagnostic and treatment paradigm for this disease.

Reperfusion therapy in acute ischemic stroke: dawn of a new era?

Following the success of recent endovascular trials, endovascular therapy has emerged as an exciting addition to the arsenal of clinical management of patients with acute ischemic stroke (AIS). In this paper, we present an extensive overview of intravenous and endovascular reperfusion strategies, recent advances in AIS neurointervention, limitations of various treatment paradigms, and provide insights on imaging-guided reperfusion therapies. A roadmap for imaging guided reperfusion treatment workflow in AIS is also proposed. Both systemic thrombolysis and endovascular treatment have been incorporated into the standard of care in stroke therapy. Further research on advanced imaging-based approaches to select appropriate patients, may widen the time-window for patient selection and would contribute immensely to early thrombolytic strategies, better recanalization rates, and improved clinical outcomes.

Ischemic Strokes Due to Large-Vessel Occlusions Contribute Disproportionately to Stroke-Related Dependence and Death: A Review

Background

Since large-vessel occlusion (LVO)-related acute ischemic strokes (AIS) are associated with more severe deficits, we hypothesize that the endovascular thrombectomy (ET) may disproportionately benefit stroke-related dependence and death.

Methods

To delineate LVO-AIS impact, systematic search identified studies measuring dependence or death [modified Rankin Scale (mRS) 3–6] or mortality following ischemic stroke among consecutive patients presenting with both LVO and non-LVO events within 24 h of symptom onset.

Results

Among 197 articles reviewed, 2 met inclusion criteria, collectively enrolling 1,467 patients. Rates of dependence or death (mRS 3–6) within 3–6 months were higher after LVO than non-LVO ischemic stroke, 64 vs. 24%, odds ratio (OR) 4.46 (CI: 3.53–5.63, p < 0.0001). Mortality within 3–6 months was higher after LVO than non-LVO ischemic stroke, 26.2 vs. 1.3%, OR 4.09 (CI: 2.5–6.68), p < 0.0001. Consequently, while LVO ischemic events accounted for 38.7% (CI: 21.8–55.7%) of all acutely presenting ischemic strokes, they accounted for 61.6% (CI: 41.8–81.3%) of poststroke dependence or death and 95.6% (CI: 89.0–98.8%) of poststroke mortality. Using literature-based projections of LVO cerebral ischemia patients treatable within 8 h of onset, ET can be used in 21.4% of acutely presenting patients with ischemic stroke, and these events account for 34% of poststroke dependence and death and 52.8% of poststroke mortality.

Conclusion

LVOs cause a little more than one-third of acutely presenting AIS, but are responsible for three-fifths of dependency and more than nine-tenths of mortality after AIS. At the population level, ET has a disproportionate benefit in reducing severe stroke outcomes.

Incorporation of relative cerebral blood flow into CT perfusion maps reduces false ’at risk' penumbra

Purpose

The region defined as ‘at risk’ penumbra by current CT perfusion (CTP) maps is largely overestimated. We aimed to quantitate the portion of true ‘at risk’ tissue within CTP penumbra and to determine the parameter and threshold that would optimally distinguish it from false ‘at risk’ tissue, that is, benign oligaemia.

Methods

Among acute stroke patients evaluated by multimodal CT (NCCT/CTA/CTP) we identified those that had not undergone endovascular/thrombolytic treatment and had follow-up NCCT. Maps of absolute and relative CBF, CBV, MTT, TTP and Tmax as well as summary maps depicting infarcted and penumbral regions were generated using the Intellispace Portal (Philips Healthcare, Best, Netherlands). Follow-up CT was automatically co-registered to the CTP scan and the final infarct region was manually outlined. Perfusion parameters were systematically analysed – the parameter that resulted in the highest true-negative-rate (ie, proportion of benign oligaemia correctly identified) at a fixed, clinically relevant false-negative-rate (ie, proportion of ‘missed’ infarct) of 15%, was chosen as optimal. It was then re-applied to the CTP data to produce corrected perfusion maps.

Results

Forty seven acute stroke patients met selection criteria. Average portion of infarcted tissue within CTP penumbra was 15%±2.2%. Relative CBF at a threshold of 0.65 yielded the highest average true-negative-rate (48%), enabling reduction of the false ‘at risk’ penumbral region by ~half.

Conclusions

Applying a relative CBF threshold on relative MTT-based CTP maps can significantly reduce false ‘at risk’ penumbra. This step may help to avoid unnecessary endovascular interventions.

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.

Restrictive Arteriopathy in Late-Onset Pompe Disease: Case Report and Review of the Literature

Late-onset Pompe disease (LOPD) is an adult type of classical Pompe disease and presents without cardiomyopathy. Neuroimaging in LOPD is typically limited to posterior circulation and involves dilative arteriopathy, especially dolichoectasia and intracranial aneurysms. We report an interesting case of an established diagnosis of asymptomatic LOPD in a young man with a restrictive-variant pattern in posterior vasculature. We discuss the clinical presentation, neuroimaging, existing literature, and prognosis in vascular variants of LOPD.

Reporting Compliance of Stroke Trials: Cross-Sectional Analysis

BACKGROUND

The FDA mandates timely reporting of all clinical trials conducted in the United States. However, often the results are not reported in a timely manner, resulting in wastage of finite resources. We assessed the reporting of results of completed stroke trials and compared the reporting trends between U.S. and non-U.S. stroke trials.

METHODS

We assessed consecutive clinical stroke trials registered as completed in ClinicalTrials.gov between January 1, 2008 and January 1, 2015. Descriptive data collected included study phase, study type, participant age, number of enrolled patients, study locations, start and primary completion dates, result availability, time to reporting (months), sponsorship, funding sources, and publication status. We also performed manual search for stroke trials in Pubmed, Web of Science, and Google scholar.

RESULTS

Out of a total 140 completed trials, 39 trials (35,359 patients) involved at least 1 U.S. center and 101 trials (58,542 patients) were conducted in non-U.S. centers. Of the trials involving at least a single U.S. center, 31 of 39 (79%) reported their results, whereas only 6 of 31 (19%) reported their results within 1 year. Of the trials conducted at non-U.S. centers, 72 of 101 (71%) reported their results, whereas results for 24 of 72 (33%) trials were available within a year of completion. The time to reporting of results was significantly lower for all the included clinical trials in the 2012-2014 period (P < .001, Cohen's d = .726) as compared to the 2008-2011 period.

CONCLUSION

Only one-fifth of completed stroke trials involving at least a single U.S. center report their results within 1 year. Additionally, every fifth completed trial involving stroke patients at U.S. centers remain unreported.

Cerebral regions preserved by successful endovascular recanalization of acute M1 segment occlusions: a voxel based analysis

OBJECTIVE

To identify cerebral regions preserved by successful recanalization of the middle cerebral artery M1 segment and their association with early clinical outcome.

METHODS

47 patients who underwent endovascular treatment for acute unilateral M1 segment occlusion were included. Successful recanalization was defined by a modified thrombolysis in cerebral infarction score of 2b/3. Final infarct volumes were segmented on follow-up MRI/CT, 2-7 days post-symptom onset. The differences in topography of infarct lesions associated with successful vs unsuccessful recanalization were assessed using voxel-based analysis. Favourable outcome was defined by a modified Rankin Scale score ≤2 at discharge, and disability/death by score >2.

RESULTS

Successful recanalization of M1 segment occlusion was achieved in 26/47 (55%) patients, which was associated with higher rate of favourable outcome (54% vs 9%, p = 0.002) and smaller final infarct volumes (34.3 ± 43.7 vs 98.1 ± 47.7 ml, p < 0.001). In voxel-based analysis, patients with successful recanalization had a lower rate of infarction in precentral gyrus and posterior insular ribbon compared with those without recanalization. Favourable outcome was achieved in 16 (34%) patients, who were younger (62.2 ± 13.9 vs 70.9 ± 13.9, p = 0.048), had higher rate of successful recanalization (88% vs 39%, p = 0.002) and had smaller infarct volumes (25.2 ± 23.6 vs 82.2 ± 57.1 ml, p < 0.001) compared with those with disability/death. In voxel-based analysis, infarction of the insula, precentral gyrus, middle centrum semiovale and corona radiata were associated with disability/death.

CONCLUSION

Successful endovascular recanalization of acute M1 segment occlusion tends to preserve posterior insular ribbon and precentral gyrus from infarction; and infarction of these regions was associated with higher rates of disability/death. Advances in knowledge: The knowledge of the topographic location of potentially salvageable cerebral tissue can provide additional information for treatment triage and selection of patients with acute stroke for endovascular treatment based on the "areas at risk" rather than the "volume at risk". Also, such knowledge can help with preferential recanalization, where the neurointerventionalist may choose to preferentially recanalize certain branches supplying salvageable and eloquent cerebral regions in favour of timely reperfusion treatment.

Gyriform Infarction in Cerebral Air Embolism: Imaging Mimicker of Status Epilepticus

Cerebral air embolism (CAE) is a potentially fatal iatrogenic complication related to common procedures including central venous catheter (CVC) removal. We report an interesting case of CAE related to CVC removal that was further complicated with status epilepticus. Neuroimaging of CAE and status epilepticus could pose diagnostic dilemmas and require consideration of wide diagnostic differentials. We discuss the clinical presentation, mechanism, and diagnostic approach, especially neuroimaging to differentiate various etiologies in CAE patients.

Interaction of incidental microbleeds and prior use of antithrombotics with early hemorrhagic transformation: Causative or protective?

BACKGROUND

Gradient echo (GRE) sequence of magnetic resonance imaging (MRI) is a sensitive tool to detect hemorrhagic transformation (HT) and old cerebral microbleeds (CMBs). Presence of CMBs and prior use of antithrombotics pose a risk of HT in ischemic stroke. We evaluated the association of CMBs and antithrombotic use with resultant HT in acute ischemic stroke (AIS).

METHODS

This retrospective study included AIS patients admitted to our center between January 2009 and August 2010 who underwent GRE-weighted MRI within 48 h of admission. Demographic and clinical data including diabetes mellitus, hypertension, hyperlipidemia, prior intake of antiplatelets/anticoagulants/statins, and presence of CMBs at admission were collected and compared between patients who developed HT and those who did not. We did a multivariate analysis using logistic regression to assess the effect of CMBs and prior use of antithrombotic agents on the risk of development for early HT in ischemic stroke.

RESULTS

Of 529 AIS patients, 81 (15%) were found to have HT during the initial hospital course. CMBs were found in only 9 of 81 patients (11%) with HT and in 40 out of remaining 448 patients (9%) who did not develop HT. The presence of CMBs was not associated with increased risk of HT (P = 0.53). However, prior use of antiplatelets (33% vs. 47% in the patients without HT, P = 0.02) was associated with decreased risk of HT in ischemic stroke.

CONCLUSION

Presence of incidental CMBs was not associated with increased risk for early HT of an ischemic stroke. Interestingly, the prior intake of antiplatelets was found to be protective against HT of ischemic stroke.

Atypical case of perimesencephalic subarachnoid hemorrhage

Perimesencephalic subarachnoid hemorrhage (PM-SAH) refers to intracranial hemorrhage located in the perimesencephalic cistern. The etiology remains mainly unclear, although venous leakage or rupture has been postulated. We report an interesting case of a 57-year-old healthy man who presented initially with PM-SAH with worsening of subcortical lesions on follow-up neuroimaging. Histopathological examination demonstrated cerebral amyloid angiopathy with perivascular inflammation.

Wake-up stroke: Dawn of a new era

Wake-up stroke or stroke with unclear onset of symptoms is known to occur in one-fourth of ischemic stroke patients. These patients are not considered for thrombolytic therapy based on time designation of their symptom onset as per the current guidelines. Observational studies have investigated the pathophysiology and suggested actual onset of symptoms to be approximate to the awakening time for these patients. Use of advanced imaging modalities in these patients tends to identify favorable patient profiles for thrombolysis. Results of the ongoing trials will likely beckon a seminal juncture in stroke therapy and deliver critical modifications in the current treatment guidelines for thrombolysis in this substantial, yet neglected, group of stroke patients. In this article, we have reviewed the predisposing factors, preferred imaging modalities and various ongoing thrombolytic and endovascular trials to date for patients with unclear time of symptom onset or who wake up with stroke symptoms.

Management of the Interventional Stroke Patient

OPINION STATEMENT

The acute treatment of major ischemic stroke has been revolutionized by strong and consistent evidence from multiple randomized trials. Endovascular treatment by mechanical thrombectomy will be increasingly chosen as an adjunctive or alternative to intravenous thrombolysis. To apply this form of stroke treatment is associated with the challenge of optimal periinterventional treatment. The patient has to be identified, counselled, prepared, monitored, cardiovascularly stabilized, possibly sedated and ventilated, and postprocedurally treated in the optimal way. However, most aspects of periinterventional treatment have as yet not been clarified and require prospective research. Among these, the question of general anesthesia vs conscious sedation has received most attention and may be the most crucial one. Based on a great amount of retrospective data, it appears reasonable to start the intervention under conscious sedation of the non-intubated patient with standby measures for emergent intubation, until prospective randomized trials have clarified that issue. Periinterventional management will significantly affect the success of recanalization.