Hyperdense sylvian fissure MCA "dot" sign: A CT marker of acute ischemia

Acute Stroke With Hyperdense Middle Cerebral Artery (MCA) Sign in an Adolescent Female With Tyrosine Kinase Inhibitor Treatment-What You Need to Know

BACKGROUND

Acute stroke in an adolescent patient is a rare phenomenon. Tyrosine kinase inhibitors (TKIs) are newer targeted anticancer medications without widespread side effects typically associated with traditional chemotherapy. However, recent literature reveals several potential life-threatening side effects.

CASE REPORT

We present an unusual case of acute stroke with hyperdense middle cerebral artery (MCA) sign, in a 16-year-old female with a history of rhabdomyosarcoma and recent treatment with pazopanib, a tyrosine kinase inhibitor (TKI). The patient developed sudden right-sided weakness at school. She was brought to the emergency department (ED) by her parents. Prompt diagnosis with noncontrast computed tomography (CT)-brain and CT angiogram of head and neck followed by immediate administration of thrombolytic treatment with alteplase and referral for mechanical thrombectomy resulted in a successful restoration of blood flow and a favorable clinical outcome. This paper highlights the importance of recognizing stroke symptoms in young patients with a history of malignancy, discusses the risks associated with TKI treatment, and the efficacy of the treatment modalities employed. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Emergency physicians should be mindful of the many new targeted anticancer therapies and their potential deleterious side effects. Due to the lack of pediatric stroke guidelines, adult stroke guidelines may be applied in the management of adolescent patients with acute stroke. Emergency physicians should also be able to recognize a hyperdense MCA sign on a noncontrast CT scan of the brain in a patient presenting with anterior circulation stroke symptoms.

Feasibility of thin-slice, low noise images created using multi-kernel synthesis to replace multiple image series in head CT

BACKGROUND

SynthesiZed Improved Resolution and Concurrent nOise reductioN (ZIRCON) is a multi-kernel synthesis method that creates a single series of thin-slice computed tomography (CT) images displaying low noise and high spatial resolution, increasing reader efficiency and minimizing partial volume averaging.

PURPOSE

To compare the diagnostic performance of a single set of ZIRCON images to two routine clinical image series using conventional CT head and bone reconstruction kernels for diagnosing intracranial findings and fractures in patients with trauma or suspected acute neurologic deficit.

MATERIAL AND METHODS

In total, 50 patients underwent clinically indicated head CT in the ER (15 normal, 35 abnormal cases). A non-reader neuroradiologist established the reference standard. Three neuroradiologists reviewed two routine clinical series (head and bone kernels) and a single ZIRCON series, detecting intracranial findings or fractures and rating confidence (0-100). Sensitivity, specificity, and jackknife free-response receiver operating characteristic (JAFROC) figure of merit (FOM) were compared (limit of non-inferiority: -0.10).

RESULTS

ZIRCON and conventional images demonstrated comparable performance for fractures (sensitivity: 51.5% vs. 54.5%; specificity: 40.2% vs. 34.2%) and intracranial findings (sensitivity: 88.2% vs. 91.4%; specificity: 77.2% vs. 73.7%).The estimated difference of JAFROC FOM demonstrated ZIRCON non-inferiority for acute pathologies overall (0.003 [95% CI=-0.051-0.057]) and fractures (0.048 [95% CI=-0.050-0.145]) but not for intracranial findings alone (-0.024 [95% CI=-0.100-0.052]).

CONCLUSION

Thin-slice, low noise, and high spatial resolution images can be created to display intracranial findings and fractures replacing multiple images series in head CT with similar performance. Future studies in more patients and further algorithmic development are warranted.

Dual-Energy Computed Tomography Virtual Noncalcium Imaging of Intracranial Arteries in Acute Ischemic Stroke: Differentiation Between Acute Thrombus and Calcification

OBJECTIVE

Hyperdense artery sign (HAS) on noncontrast brain computed tomography (CT) indicates an acute thrombus within the cerebral artery. It is a valuable imaging biomarker for diagnosing large-vessel occlusion; however, its identification may be challenging with the presence of vascular calcification. Dual-energy CT virtual noncalcium (VNCa) imaging using a 3-material decomposition algorithm is helpful for differentiating between calcification and hemorrhage. This study aimed to clarify the potential of VNCa imaging for differentiating HAS from vascular calcification.

METHODS

Patients with acute ischemic stroke and large-vessel occlusion identified on MR angiography, who also underwent noncontrast dual-energy CT, were included. The 80 kV/Sn 140 kV mixed images, with a weighting factor of 0.4, were considered 120 kVp-equivalent images. Postprocessing using a 3-material decomposition algorithm to differentiate between calcium (Ca), cerebrospinal fluid, and hemorrhage was performed via a commercially available 3-dimensional workstation. A mixed image, VNCa image, color-coded Ca image, and color-coded Ca image with VNCa image overlay (color-coded Ca-overlay image) were obtained, and axial reconstruction with a 1-mm slice thickness was performed for each image type. Two experienced neuroradiologists conducted imaging evaluations in consensus.

RESULTS

Thirty-four patients (mean age, 76.0 years; 21 male and 13 female patients) were included. The mixed and VNCa images revealed an HAS (indicating an acute clot) corresponding to the large-vessel occlusion site in 30 patients. Among them, the VNCa and color-coded Ca-overlay images enabled clear differentiation between the acute thrombus and adjacent vessel wall calcification in 5 patients. Among the other 4 patients, the VNCa, Ca-overlay, and Ca images identified calcified cerebral emboli in the M1 segment in 1 patient. For the other 3 patients, no high attenuation corresponding to magnetic resonance angiography findings was observed in any of the mixed, VNCa, Ca-overlay, or Ca images.

CONCLUSIONS

VNCa and color-coded Ca-overlay images obtained via dual-energy brain CT enabled differentiation of acute thrombus from vessel wall calcification and calcified cerebral emboli in patients with acute ischemic stroke.

Diagnostic Accuracy of Hyperdense Artery Sign in Early Detection of Middle Cerebral Artery Infarction: A Cross-Sectional Validation Study

Background

Hyperdense middle cerebral artery sign (HMCAS) on a non-enhanced multidetector computed tomography (MDCT) scan is considered an important radiological marker in detecting acute arterial thrombotic occlusion, and it is one of the earliest signs of ischemic cerebrovascular accident (CVA). This finding has been observed within 90 min of symptom onset. Modern approaches to patients with cerebral infarction emphasize early diagnosis and management.

Purpose

To determine the diagnostic accuracy of hyperdense artery signs in early detection of middle cerebral artery (MCA) infarction on non-contrast-enhanced MDCT scan using Magnetic Resonance Angiography (MRA) within 24 h as the gold standard for definitive diagnosis.

Method

A total of 140 patients aged 35-70 years, referred to the radiology department of Aga Khan University Hospital with clinical suspicion of acute cerebral infarction, were included. After clinical suspicion of acute infarction, the patient underwent an initial complete MDCT scan of the brain, which was performed using Aquilion ONE 640 slice MDCT (Toshiba Medical Systems, Japan). Consultant radiologists, with a minimum of 5 years of experience in MDCT brain imaging, interpreted the images. Follow-up examination with MRA within 24 h was performed to confirm the diagnosis of MCA infarction.

Results

Overall sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of HMCAS in the early detection of MCA infarction on non-contrast-enhanced MDCT scan using MRA as the gold standard for definitive diagnosis was 96.20%, 93.44%, 95.0%, 95.0%, and 95.0%, respectively.

Conclusion

This study concluded that the diagnostic accuracy of hyperdense artery signs in the early detection of MCA infarction on non-contrast-enhanced MDCT scans is very high.

Automated Intracranial Clot Detection: A Promising Tool for Vascular Occlusion Detection in Non-Enhanced CT

(1) Background: to test the diagnostic performance of a fully convolutional neural network-based software prototype for clot detection in intracranial arteries using non-enhanced computed tomography (NECT) imaging data. (2) Methods: we retrospectively identified 85 patients with stroke imaging and one intracranial vessel occlusion. An automated clot detection prototype computed clot location, clot length, and clot volume in NECT scans. Clot detection rates were compared to the visual assessment of the hyperdense artery sign by two neuroradiologists. CT angiography (CTA) was used as the ground truth. Additionally, NIHSS, ASPECTS, type of therapy, and TOAST were registered to assess the relationship between clinical parameters, image results, and chosen therapy. (3) Results: the overall detection rate of the software was 66%, while the human readers had lower rates of 46% and 24%, respectively. Clot detection rates of the automated software were best in the proximal middle cerebral artery (MCA) and the intracranial carotid artery (ICA) with 88-92% followed by the more distal MCA and basilar artery with 67-69%. There was a high correlation between greater clot length and interventional thrombectomy and between smaller clot length and rather conservative treatment. (4) Conclusions: the automated clot detection prototype has the potential to detect intracranial arterial thromboembolism in NECT images, particularly in the ICA and MCA. Thus, it could support radiologists in emergency settings to speed up the diagnosis of acute ischemic stroke, especially in settings where CTA is not available.

Artificial Intelligence in Acute Ischemic Stroke Subtypes According to Toast Classification: A Comprehensive Narrative Review

The correct recognition of the etiology of ischemic stroke (IS) allows tempestive interventions in therapy with the aim of treating the cause and preventing a new cerebral ischemic event. Nevertheless, the identification of the cause is often challenging and is based on clinical features and data obtained by imaging techniques and other diagnostic exams. TOAST classification system describes the different etiologies of ischemic stroke and includes five subtypes: LAAS (large-artery atherosclerosis), CEI (cardio embolism), SVD (small vessel disease), ODE (stroke of other determined etiology), and UDE (stroke of undetermined etiology). AI models, providing computational methodologies for quantitative and objective evaluations, seem to increase the sensitivity of main IS causes, such as tomographic diagnosis of carotid stenosis, electrocardiographic recognition of atrial fibrillation, and identification of small vessel disease in magnetic resonance images. The aim of this review is to provide overall knowledge about the most effective AI models used in the differential diagnosis of ischemic stroke etiology according to the TOAST classification. According to our results, AI has proven to be a useful tool for identifying predictive factors capable of subtyping acute stroke patients in large heterogeneous populations and, in particular, clarifying the etiology of UDE IS especially detecting cardioembolic sources.

A Simplified Risk Score to Predict In-Hospital Newly-Diagnosed Atrial Fibrillation in Acute Ischemic Stroke Patients

Purpose

Atrial fibrillation (AF) is a significant cause of stroke, and newly diagnosed AF (NDAF) is typically detected in the early period of stroke onset. We aimed to identify the factors associated with in-hospital NDAF in acute ischemic stroke patients and developed a simplified clinical prediction model.

Methods

Patients with cryptogenic stroke aged 18 years or older who were admitted between January 2017 and December 2021 were recruited. NDAF was determined by inpatient cardiac telemetry. Univariable and multivariable regression analyses were used to evaluate the factors associated with in-hospital NDAF. The predictive model was developed using regression coefficients.

Results

The study enrolled 244 eligible participants, of which 52 NDAFs were documented (21.31%), and the median time to detection was two days (1-3.5). After multivariable regression analysis, parameters significantly associated with in-hospital NDAF were elderly (>75 years) (adjusted Odds ratio, 2.99; 95% confident interval, 1.51-5.91; P = 0.002), female sex (2.08; 1.04-4.14; P = 0.04), higher admission national institute of health stroke scale (1.04; 1.00-1.09; P = 0.05), and presence of hyperdense middle cerebral artery sign (2.33; 1.13-4.79; P = 0.02). The area under the receiver operating characteristic curve resulted in 0.74 (95% CI 0.65-0.80), and the cut-point of 2 showed 87% sensitivity and 42% specificity.

Conclusion

The validated and simplified risk scores for predicting in-hospital NDAF primarily rely on simplified parameters and high sensitivity. It might be used as a screening tool for in-hospital NDAF in stroke patients who initially presumed cryptogenic stroke.

Neuroimaging of Acute Ischemic Stroke: Multimodal Imaging Approach for Acute Endovascular Therapy

Advances in acute ischemic stroke (AIS) treatment have been contingent on innovations in neuroimaging. Neuroimaging plays a pivotal role in the diagnosis and prognosis of ischemic stroke and large vessel occlusion, enabling triage decisions in the emergent care of the stroke patient. Current imaging protocols for acute stroke are dependent on the available resources and clinicians' preferences and experiences. In addition, differential application of neuroimaging in medical decision-making, and the rapidly growing evidence to support varying paradigms have outpaced guideline-based recommendations for selecting patients to receive intravenous or endovascular treatment. In this review, we aimed to discuss the various imaging modalities and approaches used in the diagnosis and treatment of AIS.

Associations between early ischemic signs on non-contrast CT and time since acute ischemic stroke onset: A scoping review

PURPOSE

Onset to imaging (OTI) time is a crucial factor in determining treatment eligibility for acute ischemic stroke patients, since the treatments are time-dependent. Patients with an unknown OTI time are often excluded from treatment, or advanced imaging is needed, which is not widely and readily available. As non-contrast CT (NCCT) is part of the standard stroke protocol, estimating OTI time using only NCCT would be valuable for patients with an unknown OTI time. Early ischemic signs (EISs) visible on NCCT might be fit for this purpose if an association between these signs and OTI time exists. This scoping review aims to provide an overview of the literature that associated OTI time with qualitative or quantitative EISs, including the hyperdense artery sign (HAS), decrease in grey matter-white matter differentiation, hypodensity, and mass effect.

METHOD

The prevalence of the EISs at specific OTI times is assessed, and previously presented associations between the EISs and OTI time are reported.

RESULTS

The EIS prevalence varied between the studies. The HAS prevalence decreased after 6 h since onset. The hypodensity prevalence increased with increasing OTI time. Studies quantifying the extent of hypodensity could distinguish patients within and beyond treatment time windows, indicating its potential to estimate OTI time. Finally, mass effect prevalence was seen more often at later OTI times.

CONCLUSIONS

It is concluded that, despite the high prevalence variability between studies, some associations between EISs and OTI time can be observed. These are potentially valuable in estimating OTI time and supporting treatment decisions.

Visualization of thrombus using iterative reconstruction and maximum intensity projection of thin-slice CT images

OBJECTIVE

Iterative reconstruction (IR) is a noise reduction method that facilitates the synthesis of maximum intensity projection (MIP) from a larger number of slices while maintaining resolution. The present study aimed to analyze whether CT evaluation using IR and MIP is ideal for thrombus evaluation of large vessel occlusions in patients with acute ischemic stroke.

METHODS

Three types of images for each patient were reconstructed and categorized into three groups: the "conventional group," evaluated using 0.5-mm slice CT, the "MIP group," evaluated using 0.5-mm slice CT processed with MIP, and the "IR + MIP group," evaluated with 0.5-mm slice CT processed with IR and MIP. Noise and image quality were evaluated with noise standard deviation (Noise SD) and contrast-to-noise ratio (CNR). Three experts evaluated the thrombus edge coordinates, made a visual assessment, and compared the data with the digital subtraction angiography (DSA) of the mechanical thrombectomy.

RESULTS

Twenty-nine patients with cerebral infarction having large vessel occlusion were included in this study. The IR + MIP group had a lower Noise SD and a statistically higher CNR, leading to more favorable image evaluations. The thrombus assessment showed no inter-rater variability in thrombus edge identification, and the visual assessment and comparison with DSA were statistically better in the IR + MIP group.

CONCLUSIONS

IR reduces noise and improves resolution. MIP in combination with IR facilitates visualization of thrombus.

Usefulness of maximum intensity projection images of non-enhanced CT for detection of hyperdense middle cerebral artery sign in acute thromboembolic ischemic stroke

PURPOSE

To compare the sensitivity of the hyperdense middle cerebral artery (MCA) sign between maximum intensity projection (MIP) and conventional averaged images in patients with acute focal neurological deficits with acute thromboembolic MCA occlusion (MCA occlusion group) and patients with acute focal neurological deficits without MCA occlusion (control group).

MATERIALS AND METHODS

Initial computed tomography (CT) scans on admission were reconstructed with 5 mm thickness at every 3 mm interval for averaged and MIP images from 1 mm thickness non-contrast axial source images. Images were obtained from 30 cases each in the MCA occlusion and control groups. The CT values in the region of interests (ROIs) on the affected and unaffected sides of the MCA were compared. To compare CT values among subjects, the CT values were normalized by obtaining a ratio on the affected and unaffected sides, and the normalized CT values were analyzed using the receiver operating characteristic (ROC) curve.

RESULTS

The hyperdense MCA sign was visually detected on MIP images in 90% cases and on 5 mm averaged images in only 57% cases in the MCA occlusion group. Based on the ROC analysis of the normalized ratio on the affected and unaffected sides, area under the curve of MIP image and averaged image was 0.941 and 0.655, respectively. On MIP images, the optimal threshold of the ratio on the affected and unaffected sides was 1.152 (sensitivity: 90.0%, and specificity: 93.3%).

CONCLUSION

The hyperdense MCA sign sensitivity on 5 mm MIP images was significantly higher than that on conventional 5 mm averaged CT images. This could be useful for the early initiation of proper therapy for patients with acute focal neurological deficits.

Thin Slice Unenhanced Brain CT Can Detect Aneurysms Larger than 7 mm

Purpose:

To evaluate the detection rate of intracranial aneurysms on reconstructed thin slice non enhanced CT (NECT) scans.

Methods:

NECT scans from 34 patients with 35 aneurysms and 35 individuals without aneurysms were collected. Thin slice maximum intensity projections of the NECT scans were reconstructed. One observer evaluated the native images twice with a time interval of six month between both passes with respect to the prevalence and location of an aneurysm. The size and location of the aneurysms were evaluated in corresponding CT-Angiography and Time of flight datasets. A logit regression analysis was performed with size and location as dependent variables. 2 × 2 tables were constructed. The sensitivity and false negative rate were calculated for aneurysms with 0–6.9 mm, 7–9.9 mm and 10–20 mm and the under the curve (AUC) was calculated.

Results:

The overall detection rate of the aneurysms was 63% for the first pass and 66% for the second pass in the reconstructed NECT scans. The detection rate of aneurysms is size dependent. The sensitivity to detect aneurysms with a size of 0–6.9 mm was 0.09 and 0.03, for aneurysms with a size of 7–9.9. mm was 0.8 and 0.7 and for aneurysms with a size of 10–20 mm was 0.92 for both passes.

The AUC was 0.77 for the first pass and 0.78 for the second pass.

Conclusions:

NECT scans can be used to detect a significant proportion of intracranial aneurysms larger than 7 mm if properly displayed and reconstructed. These patients should receive further vascular imaging to prevent future aneurysm related subarachnoid hemorrhage.

Hyperdense Artery Sign in Patients With Acute Ischemic Stroke-Automated Detection With Artificial Intelligence-Driven Software

Background

Hyperdense artery sign (HAS) on non-contrast CT (NCCT) can indicate a large vessel occlusion (LVO) in patients with acute ischemic stroke. HAS detection belongs to routine reporting in patients with acute stroke and can help to identify patients in whom LVO is not initially suspected. We sought to evaluate automated HAS detection by commercial software and compared its performance to that of trained physicians against a reference standard.

Methods

Non-contrast CT scans from 154 patients with and without LVO proven by CT angiography (CTA) were independently rated for HAS by two blinded neuroradiologists and an AI-driven algorithm (Brainomix®). Sensitivity and specificity were analyzed for the clinicians and the software. As a secondary analysis, the clot length was automatically calculated by the software and compared with the length manually outlined on CTA images as the reference standard.

Results

Among 154 patients, 84 (54.5%) had CTA-proven LVO. HAS on the correct side was detected with a sensitivity and specificity of 0.77 (CI:0.66–0.85) and 0.87 (0.77–0.94), 0.8 (0.69–0.88) and 0.97 (0.89–0.99), and 0.93 (0.84–0.97) and 0.71 (0.59–0.81) by the software and readers 1 and 2, respectively. The automated estimation of the thrombus length was in moderate agreement with the CTA-based reference standard [intraclass correlation coefficient (ICC) 0.73].

Conclusion

Automated detection of HAS and estimation of thrombus length on NCCT by the tested software is feasible with a sensitivity and specificity comparable to that of trained neuroradiologists.

The middle cerebral artery (MCA) dot sign

The middle cerebral artery (MCA) dot sign is an important radiological sign in patients presenting with acute ischemic stroke (AIS). If identified and intervened early, a good clinical outcome may be achieved.

Identifying Cerebral Large Vessel Occlusion in Acute Ischemic Stroke by MRI Positioning Scanning

Various approaches have been tried for acute ischemic stroke (AIS) treatment to shorten the time from onset to recanalization. MRI positioning scanning (PS), which must be taken before any MRI sequences, was examined whether it can detect cerebral large vessel occlusion. A total of 68 consecutive patients with AIS who underwent MRI and were treated with intravenous recombinant tissue plasminogen activator or mechanical thrombectomy at our hospital were retrospectively included in this study. Occluded vessels were identified on the axial or coronal views of PS images, and these images were compared with 3D time-of-flight MRA and digital subtraction angiogram. The sensitivities, positive predictive values (PPVs), and negative predictive values (NPVs) for internal carotid artery (ICA), the proximal M1, distal M1, and M2 segment of the middle cerebral artery occlusion were assessed, and the number of PS slices was assessed. The sensitivities of the axial slices for ICA, proximal M1, distal M1, and M2 occlusion were 62%, 21%, 35%, and 86%, respectively. The PPVs of the axial slices for ICA, proximal M1, distal M1, and M2 occlusion were 81%, 88%, 100%, and 97%, respectively, and the NPVs of the axial slices for ICA, proximal M1, distal M1, and M2 occlusion were 94%, 90%, 86%, and 100%, respectively. The detection rate for the ICA was significantly higher with three axial slices (91%) than with two slices (47%) (p <0.01). MRI PS is warranted to be referred to detect large cerebral vessel occlusion.

3D dissimilar-siamese-u-net for hyperdense Middle cerebral artery sign segmentation

The hyperdense middle cerebral artery sign (HMCAS) representing a thromboembolus has been declared as a vital CT finding for intravascular thrombus in the diagnosis of acute ischemia stroke. Early recognition of HMCAS can assist in patient triage and subsequent thrombolysis or thrombectomy treatment. A total of 624 annotated head non-contrast-enhanced CT (NCCT) image scans were retrospectively collected from multiple public hospitals in Hong Kong. In this study, we present a deep Dissimilar-Siamese-U-Net (DSU-Net) that is able to precisely segment the lesions by integrating Siamese and U-Net architectures. The proposed framework consists of twin sub-networks that allow inputs of left and right hemispheres in head NCCT images separately. The proposed Dissimilar block fully explores the feature representation of the differences between the bilateral hemispheres. Ablation studies were carried out to validate the performance of various components of the proposed DSU-Net. Our findings reveal that the proposed DSU-Net provides a novel approach for HMCAS automatic segmentation and it outperforms the baseline U-Net and many state-of-the-art models for clinical practice.

The Quantitative Evaluation of the Density of the Segmental Branches of the MCA in Acute Ischemic Stroke Patients

AIM

The aim of this study was to assess the density of the segmental branches of the middle cerebral artery (MCA) quantitatively as a predictor of acute ischemic stroke in patients without definitive infarct findings at cerebral parenchyma by non-contrast computed tomography (CT).

CLINICAL RATIONALE FOR THE STUDY

The clinical rationale for the study is to evaluate if the measurement of Sylvian fissure dot sign (SDS) would help early management of patients with stroke at the emergency department.

METHODS

Computed tomography scans of 101 patients admitted to the emergency department with stroke symptoms and/or signs were included in the study, retrospectively. In the patient group, the quantitative density of the segmental branches of the MCA in the Sylvian fissure was measured on the affected side and the contralateral side.

RESULTS

Quantitative density of SDS was significantly higher on the ischemic side of the brain. Receiver operating characteristic (ROC) analysis showed a cut-off value of 38.5 Hounsfield units (HU) as a predictor for acute ischemic stroke, with a sensitivity and specificity of 79% and 92%, respectively.

CONCLUSION

Quantitative density of SDS on the affected side in patients without definitive cerebral infarct findings of parenchyma can be used in the emergency room as an objective predictor sign for the diagnosis of acute ischemic stroke. Considering this finding in the differential diagnosis of acute stroke patients in the emergency room has the potential to improve their clinical management, particularly for the patients without early parenchymal and vascular signs of stroke.

CT for Treatment Selection in Acute Ischemic Stroke: A Code Stroke Primer

CT is the primary imaging modality used for selecting appropriate treatment in patients with acute stroke. Awareness of the typical findings, pearls, and pitfalls of CT image interpretation is therefore critical for radiologists, stroke neurologists, and emergency department providers to make accurate and timely decisions regarding both (a) immediate treatment with intravenous tissue plasminogen activator up to 4.5 hours after a stroke at primary stroke centers and (b) transfer of patients with large-vessel occlusion (LVO) at CT angiography to comprehensive stroke centers for endovascular thrombectomy (EVT) up to 24 hours after a stroke. Since the DAWN and DEFUSE 3 trials demonstrated the efficacy of EVT up to 24 hours after last seen well, CT angiography has become the operational standard for rapid accurate identification of intracranial LVO. A systematic approach to CT angiographic image interpretation is necessary and useful for rapid triage, and understanding common stroke syndromes can help speed vessel evaluation. Moreover, when diffusion-weighted MRI is unavailable, multiphase CT angiography of collateral vessels and source-image assessment or perfusion CT can be used to help estimate core infarct volume. Both have the potential to allow distinction of patients likely to benefit from EVT from those unlikely to benefit. This article reviews CT-based workup of ischemic stroke for making tPA and EVT treatment decisions and focuses on practical skills, interpretation challenges, mimics, and pitfalls.^©RSNA, 2019.

The Hyperdense Middle Cerebral Artery Sign in Drip-and-Ship Models of Acute Stroke Management

Background

Large vessel occlusion (LVO) leads to debilitating stroke and responds modestly to recombinant tissue plasminogen activator (rt-TPA). Early thrombectomy improves functional outcomes in selected patients with proximal occlusion but it is not available in all medical facilities. The best imaging modality for triage in an acute stroke setting in drip-and-ship models is still the subject of debate.

Objectives

We aimed to assess the diagnostic value of millimeter-sliced noncontrast computed tomography (NCCT) hyperdense middle cerebral artery sign (HMCAS) in itself or associated with clinical data for early detection of LVO in drip-and-ship models of acute stroke management.

Methods

NCCT of patients admitted to the Erasme Hospital, ULB, Brussels, Belgium, for suspicion of acute ischemic stroke between January 1 and July 31, 2017, were collected. Patients with brain hemorrhages were excluded, leading to 122 cases. The presence of HMCAS on NCCT was determined via visual assessment by 6 raters blinded to all other data. An independent rater assessed the presence of LVO on digital subtraction angiography imaging or contrast-enhanced CT angiography (CTA). The sensitivity, false-positive rate (FPR), and accuracy of HMCAS and the dot sign to detect LVO were calculated. The interobserver agreement of HMCAS was assessed using Gwet's AC1 coefficient. Then, on a separate occasion, the first 2 observers rereviewed all NCCT provided with clinical clues. The sensitivity, FPR, and accuracy of HMCAS were recalculated.

Results

HMCAS was found in 21% of the cases and a dot sign was found in 9%. The mean HMCAS sensitivity was 62% (95% CI 45–79%) and its accuracy was 86% (95% CI 79–92%) for detecting LVO. The interobserver reliability coefficient was 80% for HMCAS. Combined with clinical information, HMCAS sensitivity increased to 81% (95% CI 68–94; p = 0.041) and accuracy increased to 91% (95% CI 86–96%).

Conclusion

When clinical data are provided, detection of HMCAS on thinly sliced NCCT could be enough to decide on transfer for thrombectomy in drip-and-ship models of acute stroke management, especially in situations where CTA is less available and referral centers for thrombectomy fewer and further apart.

Direct thromboaspiration efficacy for mechanical thrombectomy is related to the angle of interaction between the aspiration catheter and the clot

Background

Direct thromboaspiration has been reported as an effective mechanical treatment for acute ischemic stroke. We aimed to determine whether the angle of interaction between the aspiration catheter and the clot affects the success of clot removal in ischemic stroke patients with large vessel occlusion in the anterior and posterior circulation.

Methods

All patients treated at our institution by direct thromboaspiration as a firstline technique between January 2016 and December 2017 were enrolled in the study. We retrospectively reviewed baseline and procedural characteristics, the angle of interaction formed between the aspiration catheter and the clot, the modified Thrombolysis in Cerebral Infarction score, and the 3 month modified Rankin Scale score.

Results

85 patients underwent direct thromboaspiration as the firstline treatment during the study period. 100 direct thromboaspiration passes were performed. An angle of interaction of ≥125.5° significantly influenced the success of clot removal (P<0.001) with good sensitivity and specificity, in particular for occlusion of the middle cerebral and basilar artery. The combination of aspiration with a stent retriever based thrombectomy was a valid rescue treatment in cases of standalone direct thromboaspiration failure.

Conclusions

In our series, an angle of interaction between the aspiration catheter and the clot of ≥125.5° was significantly associated with successful clot removal. The prediction of the angle of interaction on pretreatment imaging may help operators to select the most adequate mechanical thrombectomy technique on a case by case basis.

Brain computed tomography using iterative reconstruction to diagnose acute middle cerebral artery stroke: usefulness in combination of narrow window setting and thin slice reconstruction

PURPOSE

The purpose of this study is to determine whether iterative model reconstruction (IMR) optimized for brain CT could improve the detection of acute stroke in the setting of thin image slices and narrow window settings.

METHODS

We retrospectively reviewed 27 patients who presented acute middle cerebral artery (MCA) stroke. Images were reconstructed using filtered back projection (FBP; 1- and 5-mm slice thickness) and IMR (1 mm thickness), and contrast-to-noise ratios (CNRs) of infarcted and non-infarcted areas were compared. To analyze the performance of acute MCA stroke detection, we used receiver operating characteristic (ROC) curve techniques and compared 5-mm FBP with standard and narrow window settings, and 1-mm FBP and IMR with narrow window settings.

RESULTS

The CNR in 1-mm IMR (1.1 ± 1.0) was significantly higher than in 5- (0.8 ± 0.7) and 1-mm FBP (0.4 ± 0.4) (p < 0.001). Furthermore, the average area under the ROC curve was significantly higher with 1-mm IMR with narrow window settings (0.90, 95% CI: 0.86, 0.94) than it was with 5-mm FBP (0.78, 95% CI: 0.72, 0.83).

CONCLUSION

The combination of thin image slices and narrow window settings under IMR reconstruction provide better diagnostic performance for acute MCA stroke than conventional reconstruction methods.

Multiplanar computed tomography reconstruction to aid in recognition of the middle cerebral artery "Dot" sign: The sagittal string sign

While non-contrast head computed tomography is effective in detecting blood, it is not sensitive in diagnosing hyperacute ischemic stroke. One neuroradiologic marker for early thromboembolic occlusion of the distal middle cerebral artery is the middle cerebral artery "dot" sign. The "dot" seen on the typical axial plane represents a hyperdensity of the middle cerebral artery in the Sylvian fissure. A review of medical literature was conducted via PubMed utilizing search phrases "MCA," "dot," and "sign." The review was limited to the intravenous tissue-type plasminogen activator era, 1996 and on. Articles were analyzed to determine the use of the sagittal plane of non-contrast head computed tomography to locate the middle cerebral artery "dot" sign. The search terms yielded 11 results which revealed that computed tomography reconstruction and sagittal planes were not used for detection of the middle cerebral artery "dot" signs. Our patient had no known past medical history. The initial non-contrast head computed tomography was read as having a hypodensity in the right insular region and a middle cerebral artery "dot" sign. Multiplanar reconstruction of the computed tomography demonstrated a hyperdense sagittal string-like appearance of the middle cerebral artery along the Sylvian fissure. Computed tomography angiography confirmed the M2 occlusion. This is the first report of using the head computed tomography sagittal plane for diagnosis of the middle cerebral artery "dot" sign. Incorporating multiplanar reconstruction and producing the sagittal plane may lead to a higher sensitivity of the middle cerebral artery "dot" sign. Further studies incorporating a patient cohort will be needed to determine how much the sagittal plane view augments predictive value of the middle cerebral artery "dot" sign.

Susceptibility weighted imaging in acute cerebral ischemia: review of emerging technical concepts and clinical applications

Susceptibility weighted imaging (SWI) is an essential magnetic resonance imaging sequence in the assessment of acute ischemic stroke. In this article, we discuss the physics principals and clinical application of conventional SWI and multi-echo SWI sequences. We review the research evidence and practical approach of SWI in acute ischemic stroke by focusing on the detection and characterization of thromboembolism in the cerebral circulation. In addition, we discuss the role of SWI in the assessment of neuroparenchyma by depiction of asymmetric hypointense cortical veins in the ischemic territory (surrogate tissue perfusion), detection of existing microbleeds before stroke treatment and monitoring for hemorrhagic transformation post-treatment. In conclusion, the SWI sequence complements other parameters in the stroke magnetic resonance imaging protocol and understanding of the research evidence is vital for practising stroke neurologists and neuroradiologists.

Thrombolysis in Real Time: Demonstration of Revascularization with Intravenous Thrombolysis Therapy in the CT Scanner

BACKGROUND AND PURPOSE

Administration of intravenous tissue plasminogen activator (tPA) in the computed tomography (CT) scanner has been recently implemented at our institution, as a means to decrease door-to-needle time. This change in protocol provided us a unique opportunity to visualize imaging signs of early recanalization.

METHODS

We evaluated patients who presented with acute ischemic stroke both before and after a change in protocol for intravenous tPA administration. We identified 10 patients who received tPA on the CT scanner and 22 patients who received tPA after CT imaging was complete. Early recanalization was defined as distal migration of thrombus or disappearance of thrombus between initial phases of imaging, large territory of diminished mean transit time on initial perfusion CT, large territory of increased cerebral blood flow on initial perfusion CT, and/or large territory of increased cerebral blood volume on initial perfusion CT. Late recanalization was defined as distal migration of thrombus or disappearance of thrombus between initial and follow-up imaging, decreased attenuation of thrombus between initial and follow-up imaging, or infarcted territory on follow-up imaging smaller than the cerebral blood volume defect on initial perfusion CT.

RESULTS

In the patients who received tPA on the CT scanner, 20% demonstrated imaging evidence of early recanalization and 30% demonstrated imaging evidence of late recanalization. In the patients who received tPA after CT imaging, 57% demonstrated imaging evidence of late recanalization.

CONCLUSION

Early recanalization of large-vessel occlusion after intravenous thrombolysis results in unique imaging findings.

Thrombus Characteristics Are Related to Collaterals and Angioarchitecture in Acute Stroke

Background

We have theorized that clots with stasis are longer. We therefore explored the relationship between thrombus imaging characteristics on noncontrast computed tomography (NCCT) and magnetic resonance imaging (MRI) with clot length and pial collaterals on baseline computed tomography angiography (CTA).

Methods

Prospective study of acute ischemic stroke patients (2005-2009) from Keimyung University. Patients with known stroke symptom onset time, baseline CTA, MRI, and with M1-Middle Cerebral Artery (MCA)±intracranial internal carotid artery (ICA) occlusions were included. Clot length and pial collaterals were measured on baseline CTA.

Results

A total of 104 patients (mean age 65.1±12.28 years, 56.7% male, median baseline National Institutes of Health Stroke Scale 13) with intracranial ICA + MCA (n=50) or isolated M1-MCA (n=54) occlusions were included. Hyperdense sign on NCCT had a median clot length of 42.3 mm versus 29.5 mm when hyperdense negative (p=0.02). Clots showing blooming artifact on gradient recall echo MRI had a median length of 39.1 mm versus 24.5 mm without blooming (p=0.005). Patients with poor baseline collaterals on CTA had longer clots than those with intermediate/good collaterals (median clot length 49.4 mm vs 34.9 mm vs 20.5 mm respectively, p<0.001). In censored logistic regression modeling, clot length was an independent predictor of hyperdense sign (p=0.05) and of the presence of blooming artifact (p=0.006).

Conclusions

Clot length and baseline collateral status are independent predictors of clot hyperdensity on NCCT and blooming artifact on gradient recall echo. Longer clots are more likely to be hyperdense and to bloom more, probably because portions of these clots are freshly formed locally due to of stasis of blood around the original clot. This stasis could be because of poor collaterals and inefficient angio-architecture within the cerebral arterial tree.

Susceptibility Vessel Sign for Intra-arterial Thrombus in Acute Posterior Cerebral Artery Infarction

BACKGROUND

Susceptibility vessel sign (SVS) on susceptibility-weighted imaging (SWI) has a high sensitivity and specificity to detect the intra-arterial thrombus in anterior circulation stroke. However, SVS has not been evaluated in posterior circulation stroke.

METHODS

We reviewed the data from patients with acute posterior cerebral artery (PCA) infarction within 24 hours from stroke onset. To elucidate the usefulness of SVS for the detection of intraluminal thrombus in acute PCA infarction, the frequency and location of SVS were compared with those of occlusion on magnetic resonance angiography (MRA) and hyperdense PCA sign on computed tomography (CT).

RESULTS

Twenty-five patients with acute PCA infarction were enrolled in the study. The SVS was found in 92% (23 of 25). MRA showed occlusions in 64% (16 of 25). The SVS was identified in 100% (16 of 16) of patients with occlusion on MRA. Patients without occlusion on MRA also showed the SVS in 78% (7 of 9; P = .0233). The positive SVS without occlusion on MRA was mainly identified in patients with occlusion of distal branches of PCA; P3 segment in 4 and P4 segment in 3. However, the hyperdense PCA sign on CT showed in only 8% (2 of 25) of all patients; its sensitivity was significantly lower than those of the SVS on SWI (P < .001).

CONCLUSIONS

SWI is more sensitive than MRA for the detection of intraluminal thrombus, especially peripheral one, in patients with acute ischemic stroke of the PCA territory. In addition, irrespective of thrombus location, SWI is significantly superior to CT in detecting thrombus in acute PCA infarction.

Telemedical Brain Computed Tomography Misinterpretation by Stroke Neurologists Is Not Associated with Thrombolysis-Related Intracranial Hemorrhage

BACKGROUND

The Stroke Eastern Saxony Network (SOS-NET) provides telecare for acute stroke patients. Stroke neurologists recommend intravenous thrombolysis based on clinical assessment and cerebral computed tomography (CT) evaluation using Alberta Stroke Program Early CT score (ASPECTS). We sought to assess whether ASPECTS misinterpretation by stroke neurologists was associated with thrombolysis-related symptomatic intracranial hemorrhage (sICH).

METHODS

We retrospectively analyzed consecutive SOS-NET patients treated with thrombolytics from July 2007 to July 2012. Experienced neuroradiologists re-evaluated CT scans blinded to clinical information providing reference standard. We defined ASPECTS underestimation as ASPECTS stroke neurologist--ASPECTS neuroradiologist more than 1 point. Primary outcome was sICH by European Cooperative Acute Stroke Study II criteria. Secondary outcome was unfavorable outcome at discharge defined as modified Rankin Scale scores 3 or more.

RESULTS

Of 1659 patients with acute ischemic stroke, thrombolysis was performed in 657 patients. Complete primary outcome and imaging data were available for 432 patients (median age, 75; interquartile range [IQR], 12 years; National Institutes of Health Stroke Scale score, 12 [IQR, 11]; 52.8% women). Nineteen patients (4.4%) had sICH, and 259 patients (60.0%) had an unfavorable outcome at discharge. Interobserver agreement between ASPECTS assessment was fair (κ = .51). ASPECTS underestimation was neither associated with sICH (adjusted odds ratio (OR), 1.32; 95% confidence interval (CI), .36-4.83, P = .68) nor unfavorable outcome (adjusted OR, 1.10; 95% CI, .47-2.54; P = .83).

CONCLUSIONS

Despite fair interrater agreement between stroke neurologists and expert neuroradiologists, underestimation of ASPECTS by the former was not associated with thrombolysis-related sICH in our telestroke network.

Clot characteristics on computed tomography and response to thrombolysis in acute middle cerebral artery stroke

BACKGROUND

Clinical and computer tomography angiography (CTA) correlates of hyperdense middle cerebral artery sign (HMCAS) and dot sign were revisited in patients treated for acute MCA stroke. Temporal evolution of these signs over 24 hours was assessed quantitatively by density (Hounsfield unit [HU]) measurements.

METHODS

Maximum pixel-sized HUs throughout proximal MCA and its insular fissure branches were determined in 131 patients with acute MCA stroke treated by intravenous thrombolysis and/or interventional thrombolysis/thrombectomy; 14 patients treated for vertebrobasilar stroke (VBS) and 42 nonstroke control subjects. Utility of visually determined HMCAS and dot sign, absolute HU of proximal and distal MCA, side-to-side HU ratio and difference, and hyperdense MCA burden score for the prediction of early dramatic recovery (EDR) and third-month favorable prognosis were evaluated. The clinical value of the changes in vessel hyperdensity over 24 hours was identified in subjects who received intravenous thrombolysis (99 MCA stoke and 11 VBS). A multivariate model with adjustment for age, baseline stroke severity (National Institutes of Health Stroke Scale [NIHSS]), and CTA-based modified clot burden score (mCBS) was used to determine independent predictors of short- and long-term clinical outcome.

RESULTS

The presence of HMCAS and dot sign, their density indices (maximum HU, ipsilateral-to-contralateral HU ratio, and difference), and changes in quantitative attenuation over 24 hours were not significantly associated with EDR and favorable third-month outcome in the multiple regression models, whereas NIHSS and mCBS were found to be significant independent "negative predictors" of both EDR and favorable prognosis, while age was a strong "negative indicator" only for 3-month good outcome. Average HU decrease over the first day was 5.7 HU in HMCAS (+) and 2.9 HU in dot sign (+) arteries. The densities of thrombi in MCA and insular branches were not different in subjects with and without cardioembolism.

CONCLUSIONS

CTA provides dependable (high sensitivity and specificity) information regarding clot size and location, whereas hyperdense artery signs have low sensitivity and just acceptable specificity levels in this regard. However, the prognostic and diagnostic information generated by the presence of hyperdense artery signs and temporal change in attenuation can be useful in acute stroke settings where CTA is not readily available. Quantitative measures, rather than qualitative evaluation have a higher yield in determination of temporal change of the hyperdensity signs and its possible clinical correlates.

Relation between stroke severity, patient characteristics and CT-perfusion derived blood-brain barrier permeability measurements in acute ischemic stroke

Purpose

Increased blood-brain barrier permeability (BBBP) can result from ischemia. In this study the relation between stroke severity, patient characteristics and admission BBBP values measured with CT-perfusion (CTP) was investigated in acute ischemic stroke patients.

Methods

From prospective data of the Dutch Acute Stroke Study 149 patients with a middle cerebral artery stroke and extended CTP were selected. BBBP values were measured in the penumbra and infarct core as defined by CTP thresholds, and in the contra-lateral hemisphere. The relation between stroke (severity) variables and patient characteristics, including early CT signs, dense vessel sign (DVS), time to scan and National Institute of Health Stroke Score (NIHSS), and BBBP parameters in penumbra and infarct core was quantified with regression analysis.

Results

Early CT signs were related to higher BBBP values in the infarct core (B = 0.710), higher ipsi- to contra-lateral BBBP ratios (B = 0.326) and higher extraction ratios in the infarct core (B = 16.938). Females were found to have lower BBBP values in penumbra and infarct core (B = − 0.446 and − 0.776 respectively) and lower extraction ratios in the infarct core (B = − 10.463). If a DVS was present the ipsi- to contra-lateral BBBP ratios were lower (B = − 0.304). There was no relation between NIHSS or time to scan and BBBP values.

Conclusion

Early CT signs are related to higher BBBP values in the infarct core, suggesting that only severe ischemic damage alters BBBP within the first hours after symptom onset.

Hyperdense cerebral artery computed tomography sign is associated with stroke severity rather than stroke subtype

BACKGROUND

The hyperdense cerebral artery sign (HCAS) on unenhanced computed tomography (CT) in acute ischemic stroke is a valuable clinical marker, but it remains unclear if HCAS reflects clot composition or stroke etiology. Therefore, variables independently associated with HCAS were identified from a large international data set of patients treated with intravenous thrombolysis.

METHODS

All stroke patients undergoing intravenous thrombolysis from the Safe Implementation of Treatments in Stroke-EAST (SITS-EAST) database between February 2003 and December 2011 were analyzed. A general estimating equation model accounting for within-center clustering was used to identify factors independently associated with HCAS.

RESULTS

Of all 8878 consecutive patients, 8375 patients (94%) with available information about HCAS were included in our analysis. CT revealed HCAS in 19% of patients. Median baseline National Institutes of Health Stroke Scale (NIHSS) score was 12, mean age was 67 ± 12 years, and 3592 (43%) patients were females. HCAS was independently associated with baseline NIHSS (odds ratio [OR], 1.11; 95% confidence interval [CI], 1.10-1.12), vessel occlusion (OR, 5.02; 95% CI, 3.31-7.63), early ischemic CT changes (OR, 1.63; 95% CI, 1.31-2.04), year (OR, 1.07; 95% CI, 1.02-1.12), and age (10-year increments; OR, .90; 95% CI, .84-.96). Cardioembolic stroke was not associated with HCAS independently of baseline NIHSS. In different centers, HCAS was reported in 0%-50% of patients.

CONCLUSIONS

This study illustrates significant variation in detection of HCAS among stroke centers in routine clinical practice. Accounting for within-center data clustering, stroke subtype was not independently associated with HCAS; HCAS was associated with the severity of neurologic deficit.

Role of multidetector CT in the recognition of hyperdense middle cerebral artery sign (HMCAS) in patients with acute cerebral ischaemia: correlation with DWI-MRI sequences and clinical data

PURPOSE

The aim of this study was to verify the sensitivity and specificity of the hyperdense middle cerebral artery sign (HMCAS) obtained by multidetector computed tomography (CT) in predicting acute stroke, using diffusion-weighted (DW) magnetic resonance imaging (MRI) as a reference. The location of the HMCAS, the extension of the ischaemic lesion and its prognostic value were also assessed.

MATERIALS AND METHODS

The CT examinations of 654 patients with symptoms related to acute cerebral stroke were retrospectively reviewed. DW-MRI confirmed recent stroke in 175 patients. Two expert neuroradiologists analysed the CT examinations of these patients in four phases. Sensitivity, specificity and interobserver reliability was evaluated. Patients were divided into three groups according to the HMCAS site (M1-M2-M3) and the Alberta Stroke Program Early CT Score (ASPECTS) on DW-MRI was calculated. The ASPECTS average score was correlated with the National Institutes of Health Stroke Scale (NIHSS) and modified Rankin scale (mRS) at 3 months.

RESULTS

In 41 patients, the presence of HMCAS was confirmed (71 % sensitivity; 100 % specificity; Interobserver reliability k, 84 %). An inverse correlation was found by comparing the ASPECTS and NIHSS scores (Rsq = -0.206). After logistic regression analysis, HMCAS was found to be independently associated with a poor outcome (mRS >2) at 3 months after adjusting for age, NIHSS on admission, risk factors and aetiology of stroke.

CONCLUSIONS

Our study demonstrated that HMCAS obtained with multidetector CT can be detected in more than 70 % of patients with large acute ischaemic lesion and it is an unfavourable prognostic sign.

Early reperfusion rates with IV tPA are determined by CTA clot characteristics

BACKGROUND AND PURPOSE

An ability to predict early reperfusion with IV tPA in patients with acute ischemic stroke and intracranial clots can help clinicians decide if additional intra-arterial therapy is needed or not. We explored the association between novel clot characteristics on baseline CTA and early reperfusion with IV tPA in patients with acute ischemic stroke by using classification and regression tree analysis.

MATERIALS AND METHODS

Data are from patients with acute ischemic stroke and proximal anterior circulation occlusions from the Calgary CTA data base (2003-2012) and the Keimyung Stroke Registry (2005-2009). Patients receiving IV tPA followed by intra-arterial therapy were included. Clot location, length, residual flow within the clot, ratio of contrast Hounsfield units pre- and postclot, and the M1 segment origin to the proximal clot interface distance were assessed on baseline CTA. Early reperfusion (TICI 2a and above) with IV tPA was assessed on the first angiogram.

RESULTS

Two hundred twenty-eight patients (50.4% men; median age, 69 years; median baseline NIHSS score, 17) fulfilled the inclusion criteria. Median symptom onset to IV tPA time was 120 minutes (interquartile range = 70 minutes); median IV tPA to first angiography time was 70.5 minutes (interquartile range = 62 minutes). Patients with residual flow within the clot were 5 times more likely to reperfuse than those without it. Patients with residual flow and a shorter clot length (≤15 mm) were most likely to reperfuse (70.6%). Patients with clots in the M1 MCA without residual flow reperfused more if clots were distal and had a clot interface ratio in Hounsfield units of <2 (36.8%). Patients with proximal M1 clots without residual flow reperfused 8% of the time. Carotid-T/-L occlusions rarely reperfused (1.7%). Interrater reliability for these clot characteristics was good.

CONCLUSIONS

Our study shows that clot characteristics on CTA help physicians estimate a range of early reperfusion rates with IV tPA.

Imaging predictors of outcome following intravenous thrombolysis in acute stroke

Intravenous tissue plasminogen activator is the only approved medical treatment for patients with acute ischemic stroke. While it is associated with excellent clinical outcome in about 30 %, even with timely thrombolysis administration, certain strokes continue to evolve and lead to poor outcomes. Several studies have attempted to identify predictors of outcome despite timely thrombolysis. Persistence of a proximal clot burden and large vessel occlusion following thrombolysis are markers for patients who may potentially benefit from advanced treatment modalities like intra-arterial thrombolysis and thrombectomy. Timely brain imaging and interpretation play a crucial role in providing these treatment decisions. In this review, various imaging predictors of poor outcome among patients with acute ischemic stroke treated with intravenous thrombolysis are outlined. Despite identification of these imaging predictors, thrombolysis should not be withheld, as it may still be beneficial in a subset of patients. Knowledge of these predictors may set benchmarks for selecting candidates who may potentially benefit from advanced management strategies in future trials.

Proximal hyperdense middle cerebral artery sign predicts poor response to thrombolysis

The aim of our study was to compare the rapid neurological improvement after intravenous recombinant tissue-type plasminogen activator (rtPA) in patients with proximal hyperdense middle cerebral artery sign (p-HMCAS) to those without the sign and those with the distal hyperdense middle cerebral artery sign (d-HMCAS). Admission and 24 hour non-contrast CT scans of 120 patients with middle cerebral artery (MCA) territory stroke who were treated with intravenous rtPA were assessed for the presence of p-HMCAS and d-HMCAS. The sign was classified according to the site of occlusion. Rapid neurological improvement was defined as ≥50% improvement in the NIHSS score at 24 hours after thrombolysis. Rapid neurological recovery after thrombolysis was assessed and compared between the subgroups. Rapid neurological recovery was less common in the pooled group of patients with either p-HMCAS or d-HMCAS than those without the sign (p<0.01). Patients with p-HMCAS were less likely to have rapid neurological recovery than those with d-HMCAS (p<0.01). However, there was no difference in early neurological recovery between patients with d-HMCAS and those without any hyperdense sign. Our study showed that poor neurological recovery post rtPA was confined to p-HMCAS and not to d-HMCAS, indicating that these signs have quite different prognostic significance.

[Multimodal imaging protocols and their predictive role in acute stroke functional outcome]

Brain imaging plays a central role in the assessment of patients with acute ischemic stroke. Within a few minutes, modern multimodal imaging protocols can provide one with comprehensive information about prognosis, management, and outcome of the disease, and may detect changes in the intracranial structures reflecting severity of the ischemic injury depicted by four Ps: parenchyma (of the brain), pipes (i.e., the cerebral blood vessels), penumbra, and permeability (of the blood brain barrier). In this article, we have reviewed neuroradiological predictors of stroke functional outcome in the light of the aforementioned four Ps.

CT interpretation by ASPECTS in hyperacute ischemic stroke predicting functional outcomes

PURPOSE

To determine whether the Alberta Stroke Program Early CT Scores (ASPECTS) can predict posttreatment functional outcomes in hyperacute stroke patients who receive recombinant tissue-type plasminogen activator (rt-PA) treatment within 4.5 h.

MATERIALS AND METHODS

We studied 162 patients treated with rt-PA within 4.5 h of clinical onset. Of those, 29 patients (17.90 %) received rt-PA treatment between 3 and 4.5 h. Systematic CT scoring with the ASPECTS method was done. The primary outcome was the correlations between ASPECTS and the functional status at 3 months follow-up using the modified Rankin Scale.

RESULTS

Clinical variables between those who received rt-PA treatment before and after 3 h were mostly comparable except the proportion of male gender. There were 116 patients (71.60 %) who were classified as independent. Time to receive CT scan or rt-PA treatment was not significantly associated with patients' functional status. Baseline NIHSS and ASPECTS scores were significant factors associated with dependent status or death at 3 months after rt-PA treatment. The adjusted odds ratios were 1.133 [95 % confidence interval (CI), 1.047-1.226] and 0.844 (95 % CI, 0.720-0.990), respectively.

CONCLUSION

The ASPECTS predicts the functional status of acute stroke patients who received rt-PA treatment within the 4.5-h golden period.

An automated detection method for the MCA dot sign of acute stroke in unenhanced CT

The hyperdense middle cerebral artery (MCA) dot sign representing a thromboembolus is one of the important computed tomography (CT) findings for acute stroke on unenhanced CT images. Our purpose in this study was to develop an automated method for detection of the MCA dot sign of acute stroke on unenhanced CT images. The algorithm of the method which we developed consisted of 5 major steps: extraction of the sylvian fissure region, initial identification of MCA dots based on the morphologic top-hat transformation, feature extraction of candidates, elimination of false positives (FPs) by use of a rule-based scheme, and classification of candidates using a support vector machine (SVM) classifier with four features. Our database comprised 297 CT images obtained from seven patients with the MCA dot sign. The performance of this scheme for classification of the MCA dot sign was evaluated by means of a leave-one-case out method. The performance of the classification by use of the SVM achieved a maximum sensitivity of 97.5% (39/40) at a FP rate of 1.28 per image. The sensitivity for detection of the MCA dot sign was 97.5% (39/40) with a FP rate of 0.5 per hemisphere. The method we developed has the potential to detect the MCA dot sign of acute stroke on unenhanced CT images.