Regional angiographic grading system for collateral flow: correlation with cerebral infarction in patients with middle cerebral artery occlusion

The relative cerebral blood volume (rCBV) < 42% is independently associated with hemorrhagic transformation in anterior circulation large vessel occlusion

BACKGROUND

Pretreatment CT perfusion (CTP) marker relative cerebral blood volume (rCBV) < 42% lesion volume has recently shown to predict poor collateral status and poor 90-day functional outcome. However, there is a paucity of studies assessing its association with hemorrhagic transformation (HT). Here, we aim to assess the relationship between rCBV < 42% lesion volume with HT.

METHODS

In this retrospective study, we included patients with acute ischemic stroke secondary to large vessel occlusion (AIS-LVO) of anterior circulation who had successful recanalization from two comprehensive stroke centers between 9/1/2017 and 10/01/2023. Successful recanalization was defined as modified treatment in cerebral infarction (mTICI) 2b or greater. Logistic regression analysis and ROC analysis were used to assess the relationship between rCBV <42% and HT.

RESULTS

In total, 150 patients (median age: 69 years, 58.7% female) met our inclusion criteria. On multivariable logistic regression analysis, taking into account age, sex, hypertension, hyperlipidemia, diabetes, prior stroke or transient ischemic attack, admission National Institute of Health stroke scale (NIHSS), Alberta Stroke Program Early CT Score (ASPECTS), and intravenous thrombolysis, rCBV <34% (aOR:1.01, P < .05), rCBV <38% (aOR:1.01, P < .05) and rCBV <42% (aOR:1.01, P < .05) lesion volumes were independently associated with HT. On ROC analysis rCBV < 42% (AUC = 0.61, P < .05) performed slightly better than rCBV < 38% (AUC = 0.59, P < .05) and rCBV < 34% (AUC = 0.59, P < .05) in predicting HT.

CONCLUSION

The rCBV <42% lesion volume is independently associated with HT in AIS-LVO patients who underwent successful recanalization.

The single-phase computed tomographic angiography clot burden score is independently associated with digital subtraction angiography derived American Society of Interventional and Therapeutic Neuroradiology collateral score

OBJECTIVES

The variation in quality and quantity of collateral status (CS) is in part responsible for a wide variability in extent of neural damage following acute ischemic stroke from large vessel occlusion (AIS-LVO). Single-phase CTA based clot burden score (CBS) is a promising marker in estimating CS. The aim of this study is to assess the relationship of pretreatment CTA based CBS with the reference standard Digital subtraction angiography (DSA) based American Society of Interventional and Therapeutic Neuroradiology (ASITN) CS.

METHODS

In this retrospective study, inclusion criteria were as follows: (1) Anterior circulation LVO confirmed on CTA from January 9, 2017 to January 10, 2023; (2) diagnostic CTA; and (3) underwent mechanical thrombectomy with documented DSA CS. Spearman's rank correlation analysis, multivariate logistic regression and ROC analysis was performed to assess the correlation of CTA CBS with DSA CS. P ≤ .05 was considered significant.

RESULTS

292 consecutive patients (median age = 68 years; 56.2% female) met our inclusion criteria. CTA CBS and DSA CS showed significant positive correlation (ρ = 0.51, P < .001). On multivariate logistic regression analysis CBS was found to be independently associated with DSA CS (adjusted OR = 1.83, P < .001, 95% CI: 1.54-2.19), after adjusting for age, sex, race, hyperlipidemia, hypertension, diabetes, prior stroke or transient ischemic attack, atrial fibrillation, premorbid mRS, admission NIH stroke scale, and ASPECTS. ROC analysis of CBS in predicting good DSA CS showed AUC of 0.76 (P < .001; 95% CI: 0.68-0.82). CBS threshold of > 6 has 84.6% sensitivity and 42.3% specificity in predicting good DSA CS.

CONCLUSION

CTA CBS is independently associated with DSA CS and serves as a valuable supplementary tool for CS estimation. Further research is necessary to enhance our understanding of the role of CTA CBS in clinical decision-making for patients with AIS-LVO.

ADVANCES IN KNOWLEDGE

CBS by indirectly estimating CS has shown to predict outcomes in AIS-LVO patients. No studies report association of CBS with reference standard DSA. In this study we further establish CBS as an independent marker of CS.

Neuropsychological Test Performance Differentiates Subgroups of Individuals With Adult Moyamoya Disease: A Cross-Sectional Clinical Study

BACKGROUND AND OBJECTIVES

Moyamoya disease (MMD) is a rare noninflammatory disorder involving progressive intracranial vasculopathy and impaired cerebral blood flow in the anterior circulation, resulting in stroke and cognitive impairment. We aimed to characterize cognitive impairment and the possible predictive value of sociodemographic and clinical characteristics of adults with MMD.

METHODS

This cross-sectional study examined neurocognitive performance in a group of 42 consecutive adult patients (mean age = 40.52 years; 69% female) referred for a presurgical neuropsychological evaluation. Neuropsychological functioning was assessed with a comprehensive battery, and cognitive dysfunction was defined as 1.5 SDs below the mean. Neurocognitive performance correlated with clinical/demographic characteristics and disease markers.

RESULTS

Most patients (91%) had a history of stroke, and 45% had cognitive deficits, most notably on measures of attention/speed (48%), executive functioning (47%), visuoconstruction (41%), and memory (31%-54%). Only higher educational attainment and poor collateral blood flow in the right hemisphere differentiated cognitively impaired (n = 19) and intact groups (n = 23), and MMD-related characteristics (eg, disease duration, stroke history) did not differentiate the 2 groups.

CONCLUSION

Consistent with previous work, frontal-subcortical cognitive deficits (eg, deficits in mental speed, attention, executive functioning) were found in nearly half of patients with MMD and better cognitive performance was associated with factors related to cognitive reserve. Angiographic metrics of disease burden (eg, Suzuki rating, collateral flow) and hemodynamic reserve were not consistently associated with poorer cognitive outcomes, suggesting that cognition is a crucial independent factor to assess in MMD and has relevance for treatment planning and functional status.

Numerical Modeling of Flow in the Cerebral Vasculature: Understanding Changes in Collateral Flow Directions in the Circle of Willis for a Cohort of Vasospasm Patients Through Image-Based Computational Fluid Dynamics

The Circle of Willis (CoW) is a ring-like network of blood vessels that perfuses the brain. Flow in the collateral pathways that connect major arterial inputs in the CoW change dynamically in response to vessel narrowing or occlusion. Vasospasm is an involuntary constriction of blood vessels following subarachnoid hemorrhage (SAH), which can lead to stroke. This study investigated interactions between localization of vasospasm in the CoW, vasospasm severity, anatomical variations, and changes in collateral flow directions. Patient-specific computational fluid dynamics (CFD) simulations were created for 25 vasospasm patients. Computed tomographic angiography scans were segmented capturing the anatomical variation and stenosis due to vasospasm. Transcranial Doppler ultrasound measurements of velocity were used to define boundary conditions. Digital subtraction angiography was analyzed to determine the directions and magnitudes of collateral flows as well as vasospasm severity in each vessel. Percent changes in resistance and viscous dissipation were analyzed to quantify vasospasm severity and localization of vasospasm in a specific region of the CoW. Angiographic severity correlated well with percent changes in resistance and viscous dissipation across all cerebral vessels. Changes in flow direction were observed in collateral pathways of some patients with localized vasospasm, while no significant changes in flow direction were observed in others. CFD simulations can be leveraged to quantify the localization and severity of vasospasm in SAH patients. These factors as well as anatomical variation may lead to changes in collateral flow directions. Future work could relate localization and vasospasm severity to clinical outcomes like the development of infarct.

CT perfusion based rCBF <38% volume is independently and negatively associated with digital subtraction angiography collateral score in anterior circulation large vessel occlusions

BACKGROUND

Collateral status (CS) is an important biomarker of functional outcomes in patients with acute ischemic stroke secondary to large vessel occlusion (AIS-LVO). Pretreatment CT perfusion (CTP) parameters serve as reliable surrogates of collateral status (CS). In this study, we aim to assess the relationship between the relative cerebral blood flow less than 38% (rCBF <38%), with the reference standard American Society of Interventional and Therapeutic Neuroradiology (ASITN) collateral score (CS) on DSA.

METHODS

In this prospectively collected, retrospectively reviewed analysis, inclusion criteria were as follows: (a) CT angiography (CTA) confirmed anterior circulation large vessel occlusion from 9/1/2017 to 10/01/2023; (b) diagnostic CT perfusion; and (c) underwent mechanical thrombectomy with documented ASITN CS. The ratios of the CTP-derived CBF values were calculated by dividing the values of the ischemic lesion by the corresponding values of the contralateral normal region (which were defined as rCBF). Spearman's rank correlation and logistic regression analysis were performed to determine the relationship of rCBF <38% lesion volume with DSA ASITN CS. p ≤ .05 was considered significant.

RESULTS

In total, 223 patients [mean age: 67.77 ± 15.76 years, 56.1% (n = 125) female] met our inclusion criteria. Significant negative correlation was noted between rCBF <38% volume and DSA CS (ρ = -0.37, p < .001). On multivariate logistic regression analysis, rCBF <38% volume was found to be independently associated with worse ASITN CS (unadjusted OR: 3.03, 95% CI: 1.60-5.69, p < .001, and adjusted OR: 2.73, 95% CI: 1.34-5.50, p < .01).

CONCLUSION

Greater volume of tissue with rCBF <38% is independently associated with better DSA CS. rCBF <38% is a useful adjunct tool in collateralization-based prognostication. Future studies are needed to expand our understanding of the role of rCBF <38% within the decision-making in patients with AIS-LVO.

Brain volume measured by synthetic magnetic resonance imaging in adult moyamoya disease correlates with cerebral blood flow and brain function

Moyamoya disease (MMD) is characterized by progressive arterial occlusion, causing chronic hemodynamic impairment, which can reduce brain volume. A novel quantitative technique, synthetic magnetic resonance imaging (SyMRI), can evaluate brain volume. This study aimed to investigate whether brain volume measured with SyMRI correlated with cerebral blood flow (CBF) and brain function in adult MMD. In this retrospective study, 18 adult patients with MMD were included. CBF was measured using iodine-123-N-isopropyl-p-iodoamphetamine single photon emission computed tomography. Cerebrovascular reactivity (CVR) to acetazolamide challenge was also evaluated. Brain function was measured using the Wechsler Adult Intelligence Scales (WAIS)-III/IV and the WAIS-R tests. Gray matter (GM), white matter, and myelin-correlated volumes were evaluated in six areas. Resting CBF was positively correlated with GM fractions in the right anterior cerebral arterial and right middle cerebral arterial (MCA) territories. CVR was positively correlated with GM fraction in the right posterior cerebral arterial (PCA) territory. Full-Scale Intelligence Quotient and Verbal Comprehension Index scores were marginally positively correlated with GM fractions in the left PCA territory. Processing Speed Index score was marginally positively correlated with GM fraction in the right MCA territory. The SyMRI-measured territorial GM fraction correlated with CBF and brain function in patients with MMD.

Proposal of multimodal computed tomography-based scoring system in prediction of hemorrhagic transformation in acute ischemic stroke

INTRODUCTION

The routinely used computed tomography (CT)-based workup in the setting of acute ischemic stroke (AIS) includes non-contrast brain CT, CT angiography (CTA), and CT perfusion. Several CT, CTA, CTP-based radiological biomarkers of hemorrhagic transformation (HT) were reported.

AIM OF THE STUDY

To assess the predictive value of the combined multimodal CT parameters for HT after AIS and proposal of predictive scoring scale.

METHODS

The source images of the NCCT, CTA and CTP of 282 AIS patients involving the anterior circulation (HT = 91, non-HT = 191) were retrospectively reviewed and the following biomarkers were recorded and analyzed: Early subtle ischemic signs, hyperdense middle cerebral artery sign (HMCAS) and Alberta Stroke Program Early CT Score (ASPECTS) < 7 in NCCT, large-vessel occlusion (LVO), clot burden score (CBS) < 6, large-vessel occlusion, poor collateral score (CS) and Tmax > 6 s ≥ 56.5 ml. A scoring system to predict HT based on these biomarkers was developed. Each biomarker counts for a single point with the total score ranging from 0 to 7.

RESULTS

All the aforementioned multimodal CT biomarkers and the selected cut offs were significantly associated with higher HT risk. The calculated scores were statistically significant different between the HT and the non-HT groups with AUC 0.761 (95% CI 0.703-0.819, P < 0.0000001). Rates of HT were approximately five times higher in patients with score ≥ 3.

CONCLUSION

Multimodal CT-based scoring system may provide highly reliable predictive model of hemorrhagic transformation in acute ischemic stroke.

Caveolin-1 Promoted Collateral Vessel Formation in Patients With Moyamoya Disease

Background

Caveolin-1 (Cav-1) plays pivotal roles in the endothelial function and angiogenesis postischemia. Moyamoya disease (MMD) is characterized by progressive artery stenosis with unknown etiology. We aim to determine whether serum Cav-1 levels of patients with MMD were associated with collateral vessel formation after bypass surgery.

Methods

We studied serum Cav-1 levels of 130 patients with MMD (16 with RNF213 p.R4810K mutation and 114 without RNF213 p.R4810K mutation), 15 patients with acute stroke, and 33 healthy controls. Cerebral perfusion and collateral circulation were evaluated preoperation and at 6 months after operation using pseudocontinuous arterial spin labeling MRI (pCASL-MRI) and digital subtraction angiography (DSA), respectively. Endothelial expression of Cav-1 was verified in the superficial temporal artery (STA) wall of patients with MMD by immunofluorescence double staining. We also investigated whether overexpression of Cav-1 affects cell migration and tube formation using human microvascular endothelial cells (HMECs).

Results

The serum Cav-1 level of patients with MMD intermediated between the stroke group and healthy controls and it was enhanced after the bypass surgery (681.87 ± 311.63 vs. 832.91 ± 464.41 pg/ml, p = 0.049). By 6 months after bypass surgery, patients with MMD with better collateral compensation manifested higher postoperative/preoperative Cav-1 ratio (rCav-1) than bad compensation patients. Consistently, cerebral blood flow (CBF) determined by pCASL-MRI (nCBF_MCA ratio) was positively in line with rCav-1 ratio (r = 0.8615, p < 0.0001). Cav-1 was expressed in the endothelial cells of the STA vessels of patients with MMD. Overexpression of Cav-1 by plasmid transfection in HMECs promoted tube formation and cell migration.

Conclusion

This study indicated that Cav-1 may be a potential driver to promote angiogenesis and collateral formation after bypass surgery in patients with MMD, providing a better understanding of MMD pathophysiology and potential non-surgical targets of MMD.

Pre-operative Cerebral Small Vessel Disease on MR Imaging Is Associated With Cerebral Hyperperfusion After Carotid Endarterectomy

Objectives: To determine whether pre-operative cerebral small vessel disease is associated with cerebral hyperperfusion (CH) after carotid endarterectomy (CEA). Methods: Seventy-seven patients (mean age of 66 years and 58% male) undergoing CEA for carotid stenosis were investigated using brain MRI before and after surgery. CH was defined as an increase in cerebral blood flow > 100% compared with pre-operative values on arterial spin labeling MR images. The grade or the number of four cerebral small vessel disease markers (white matter hyperintensities, lacunes, perivascular spaces, and cerebral microbleeds) were evaluated based on pre-operative MRI. Cerebral small vessel disease markers were correlated with CH by using multivariate logistic regression analysis. The cutoff values of cerebral small vessel disease markers for predicting CH were assessed by receiver-operating characteristic curve analysis. Results: CH after CEA was observed in 16 patients (20.78%). Logistic regression analysis revealed that white matter hyperintensities (OR 3.09, 95% CI 1.72-5.54; p < 0.001) and lacunes (OR 1.37, 95% CI 1.06-1.76; p = 0.014) were independently associated with post-operative CH. Receiver-operating characteristic curve analysis showed that Fazekas score of white matter hyperintensities ≥3 points [area under the curve (AUC) = 0.84, sensitivity = 81.3%, specificity = 73.8%, positive predictive value (PPV) = 44.8% and negative predictive value (NPV) = 93.8%] and number of lacunes ≥ 2 (AUC = 0.73, sensitivity = 68.8%, specificity = 78.7%, PPV = 45.8% and NPV = 90.6%) were the optimal cutoff values for predicting CH. Conclusion: In patients with carotid stenosis, white matter hyperintensities and lacunes adversely affect CH after CEA. Based on the NPVs, pre-operative MR imaging can help identify patients who are not at risk of CH.

Study on collateral circulation level and prognosis of acute ischemic stroke by 4D CTA-CTP integrated technology and serum S100B

OBJECTIVE

To evaluate the cerebral collateral circulation in patients with acute ischemic stroke (AIS) by Four-dimensional CT angiography-CT perfusion (4D CTA-CTP)-integrated technology, and to explore the feasibility of predicting the prognosis of patients with AIS by using cerebral collateral circulation and serum S100B protein concentration.

METHODS

Thirty-two patients with anterior circulation AIS who underwent 4D CTA-CTP were retrospectively analysed. The level of cerebral collateral circulation was assessed by multi-phase CT angiography (mCTA) scores and regional leptomeningeal collateral (rLMC) scores. Combined with serum S100B protein concentration, multivariate binary logistic regression was used to explore the indicators that can independently predict the prognosis of AIS neurological function.

RESULTS

Univariate analysis showed that the baseline National Institutes of Health stroke scale score, rLMC score, and mCTA score were correlated with the neurological prognosis of patients with AIS; multivariate analysis showed that mCTA cerebral collateral circulation score was the only indicator that could independently predict the neurological prognosis of AIS patients (OR = 0.065, P = 0.030). The baseline serum S100B protein concentration could not independently predict the neurological prognosis of AIS patients.

CONCLUSION

mCTA cerebral collateral circulation scores can independently predict the neurological prognosis of patients with AIS. For the assessment of neurological prognosis of AIS patients, the cerebral collateral circulation phase score is better than the regional score.

Value of pre-intervention CT perfusion imaging in acute ischemic stroke prognosis

Noninvasive imaging plays an important role in acute stroke towards diagnosis and ongoing management of patients. Systemic thrombolysis and endovascular thrombectomy (EVT) are proven treatments currently used in standards of care in acute stroke settings. The role of computed tomography angiography (CTA) in selecting patients with large vessel occlusion for EVT is well established. However, the value of CT perfusion (CTP) imaging in predicting outcomes after stroke remains ambiguous. This article critically evaluates the value of multimodal CT imaging in early diagnosis and prognosis of acute ischemic stroke with a focus on the role of CTP in delineating tissue characteristics, patient selection, and outcomes after reperfusion therapy. Insights on various technical and clinical considerations relevant to CTP applications in acute ischemic stroke, recommendations for existing workflow, and future areas of research are discussed.

Assessment of blood supply of the external carotid artery in moyamoya disease using super-selective pseudo-continuous arterial spin labeling technique

OBJECTIVES

To evaluate the diagnostic accuracy of super-selective pseudo-continuous arterial spin labeling (ss-pCASL) at depicting external carotid artery (ECA) perfusion territory in moyamoya disease (MMD).

METHODS

In total, 103 patients with MMD who underwent both ss-pCASL and digital subtraction angiography (DSA, the reference standard) were included. There were 3, 184, and 19 normal, preoperative, and postoperative MMD hemispheres, respectively. The ss-pCASL results were interpreted by two different visual inspection criteria: presence or absence and definite or indefinite ECA perfusion territory. The performance of ss-pCASL at depiction of ECA perfusion territory was compared to that of DSA. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated. The κ statistic was used to assess intermodality and inter-reader agreement.

RESULTS

When interpreted as presence or absence, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of ss-pCASL for depicting ECA perfusion territory were 78.3 %, 79.6 %, 92.5 %, 53.4 %, and 78.6 %, respectively, and the intermodality and inter-reader agreement were κ = 0.49 (CI: 0.43 - 0.55, p < 0.01) and 0.71 (CI: 0.66 - 0.76, p < 0.01), respectively. When interpreted as definite or indefinite, the respective values were 61.1%, 100%, 100%, 44.5%, 70.4%, κ = 0.42 (CI: 0.37 - 0.47, p < 0.01), and 0.90 (CI: 0.87 - 0.93, p < 0.01).

CONCLUSION

ss-pCASL has substantial sensitivity and specificity compared with DSA for depicting the presence versus absence of ECA perfusion territory in MMD. As a noninvasive method in which no ion radiation or contrast medium is needed, ss-pCASL may potentially reduce the need for repeated DSA examination.

KEY POINTS

• Super-selective pseudo-continuous arterial spin labeling (ss-pCASL) is a noninvasive vessel-selective MR technique to demonstrate perfusion territory of a single cerebral artery. • Compared with digital subtraction angiography, ss-pCASL has substantial sensitivity and specificity for depicting the perfusion territory of the external carotid artery in brain parenchyma in moyamoya disease. • ss-pCASL may potentially reduce the need for repeated DSA examination.

Mechanical Thrombectomy in Distal Residual Occlusions of the Middle Cerebral Artery after Large Vessel Recanalization in Acute Stroke: 2b or not 2b? A Pragmatic Approach in Real-Life Scenarios

BACKGROUND /OBJECTIVE

Recent studies have suggested that a recanalization grade of modified Thrombolysis in Cerebral Infarction (mTICI) score ≥2c is strongly related with good clinical outcome rather than the current therapeutic angiography target ≥2b. To achieve better recanalization, additional further maneuvers on distal residual vessel occlusion (RVO) may be required. The aim of this study was to evaluate the safety and efficacy of rescue treatment in RVOs after recanalization of large vessel occlusions in the anterior circulation.

METHODS

A single-center retrospective review of a prospectively maintained stroke databank was performed. Patients presenting with RVOs after mechanical thrombectomy on the M1/internal carotid artery terminus were included and further divided into treated and untreated groups: the former underwent additional maneuvers on RVOs, whereas the latter did not. Baseline and posttreatment clinical, radiologic, and angiographic data were compared between the 2 groups. End points included good functional outcome (modified Rankin Scale [mRS] score ≤2) rates of hemorrhagic transformations, neurologic deterioration and mortality.

RESULTS

RVOs were observed in 183/488 patients (37.5%). 74/183 (40.4%) underwent rescue treatment, showing a better outcome in terms of median 24 hours National Institutes of Health Stroke Scale score (13 vs. 18; P < 0001), 24 hours Alberta Stroke Programme Early CT Score (6 vs. 5; P < 0.001) and 3 months mRS score 0-2 (47.3% vs. 33.1%; P = 0.06). Recanalization of the superior (frontal) branch of the middle cerebral artery was particularly critical in terms of outcome. Hemorrhagic transformation was higher in the untreated group (53.6% vs. 66.6%; P = 0.1) as well as symptomatic intracranial hemorrhage (13.1% vs. 29.4%; P = 0.01). Neurologic deterioration occurred more often among untreated patients (16.2% vs. 25.7%; P = 0.1). Three complications (1.3%) occurred during rescue treatment.

CONCLUSIONS

When feasible, improving mTICI score 2a-2b recanalization to mTICI 2c/3 is safe and associated with a better clinical outcome, particularly for residual occlusions involving the superior branch of bifurcation.

Modelling the leptomeningeal collateral circulation during acute ischaemic stroke

A novel model of the leptomeningeal collateral circulation is created by combining data from multiple sources with statistical scaling laws. The extent of the collateral circulation is varied by defining a collateral vessel probability. Blood flow and pressure are simulated using a one-dimensional steady state blood flow model. The leptomeningeal collateral vessels provide significant flow during a stroke. The pressure drop over an occlusion predicted by the model ranges between 60 and 85 mmHg depending on the extent of the collateral circulation. The linear transport of contrast material was simulated in the circulatory network. The time delay of peak contrast over an occlusion is 3.3 s in the model, and 2.1 s (IQR 0.8-4.0 s) when measured in dynamic CTA data of acute ischaemic stroke patients. Modelling the leptomeningeal collateral circulation could lead to better estimates of infarct volume and patient outcome.

Quantification of pial collateral pressure in acute large vessel occlusion stroke: basic concept with patient outcomes

PURPOSE

Pial collateral perfusion to the ischemic penumbra plays a critical role in determining patient outcomes in acute stroke. We aimed to assess the validity and reliability of an intra-procedural technique for measuring and quantifying the pial collateral pressure (QPCP) to ischemic brain tissue during acute stroke secondary to LVO. QPCP measurements were correlated with standard computed tomography angiography (CTA) and digital subtraction angiography imaging assessments of pial collateral perfusion and outcomes after mechanical endovascular revascularization (MER).

METHODS

This prospective cohort study included 60 consecutive patients with middle cerebral artery (MCA)-M1 and proximal M2 occlusions. QPCP measurements were obtained during MER. The validity of QPCP measurements was evaluated using four widely accepted collateral grading scales. QPCP measurements were also analyzed as a predictor of patient outcomes utilizing National Institute of Health Stroke Scale reduction at 24 h and modified Rankin Scale (mRS) scores at 30 days.

RESULTS

QPCP measurements and QPCP ratio (QPCP/systemic mean arterial blood pressure) showed a statistically significant association with single-phase pretreatment CTA Maas and American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology binary grading scales. Patient outcomes demonstrated for every 10-unit increase in QPCP, the odds of mRS 0-2 at 30 days increased by 76% (p = 0.019).

CONCLUSION

QPCP measurements related best with the pretreatment CTA Maas collateral grading scale but were more strongly associated with patient outcomes than any of the four widely accepted collateral grading scales. Greater QPCP was significantly associated with better overall patient outcomes as defined by mRS at 30 days.

Quantitative CT angiography predicts large artery occlusion types and successful thrombectomy in acute ischemic stroke

BACKGROUND

Clinical and radiological outcomes of endovascular thrombectomy (EVT) are related to etiologies of large vessel occlusion (LVO) in acute stroke. However, preprocedural computed tomography angiography (CTA) or CT perfusion imaging can hardly distinguish embolic occlusion from atherosclerotic occlusion. We hypothesized that quantitative multiphase CTA (mCTA) of LVO may predict occlusion types and thrombectomy outcome.

METHODS

We retrospectively evaluated the consecutive stroke patients who had undergone mCTA and EVT <6 hours of onset at two independent medical centers. The intra-arterial radiodensities of Hounsfield unit (HU) were measured to examine the HUdistal/proximal ratio using receiver operating characteristic curve analysis. The derived cut-off value was re-examined in an independent cohort.

RESULTS

In the derivation cohort (n = 102), 81 patients (79.4%) were embolic occlusion without severe residual intracranial atherosclerotic stenosis (ICAS[-]) and 21 patients were atherosclerosis-related occlusion (ICAS[+]) based on digital subtraction angiography (DSA). The optimal cut-off to predict embolic occlusion was HU ratio <0.6 measured at 2 mm from the occlusion site (maximum area under the curve = 0.87; sensitivity 96%; specificity 81%). This cut-off also independently predicted successful recanalization using stent-retrievers and/or contact aspiration (modified Treatment in Cerebral Ischemia score ≥2b; p = 0.002) after adjusting for age, atrial fibrillation, and collateral circulation score, but not predicted favorable outcome at 3 months post stroke. Importantly, in the validation cohort (n = 95, 80% embolic occlusion), this HU ratio cut-off similarly predicted occlusion types and recanalization outcome, respectively.

CONCLUSION

The mCTA-based quantitative radiodensities of acute LVO provides preprocedural predictive values of DSA-determined occlusion types and thrombectomy outcomes.

FLAIR vascular hyperintensity with DWI for regional collateral flow and tissue fate in recanalized acute middle cerebral artery occlusion

PURPOSE

Fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH) extent or FVH-DWI mismatch as a primary influencing factor of clinical outcome in acute ischemic stroke is controversial. This study elucidated the regional pathophysiology and tissue fate in four types of cortical territories classified by the initial FVH and DWI findings in patients with acute proximal middle cerebral artery (M1) occlusion successfully recanalized using mechanical thrombectomy.

METHODS

We retrospectively evaluated 35 patients successfully recanalized within 24 h of acute M1 occlusion onset between 2016 and 2019. Each Alberta stroke program early CT score area of M1-M6 were categorized as group A (DWI-, FVH-), B (DWI-, FVH+), C (DWI+, FVH+), or D (DWI+, FVH-). Territorial collateral status was graded on a 4-point scale by initial angiogram. Follow-up head computed tomography (CT) findings on days 2-9 were assessed for the territorial outcome.

RESULTS

Overall, 210 cortical territories were identified; of these, 88 (41.9 %) were categorized into group A; 72 (34.3 %), group B; 37 (17.6 %), group C; and 13 (6.2 %), group D. The rate of territories with good collaterals (grade 2 or 3) significantly decreased in the order of groups as 78.3 %, 62.7 %, 27.6 %, and 0%, respectively (P_trend <.001). Conversely, the rate of territories with any hypo- or hyper-density on follow-up CT significantly increased in the order of groups as 13.4 %, 23.1 %, 88.5 %, and 85.7 %, respectively (P_trend <.001).

CONCLUSION

Categorization of cortical areas based on the FVH and DWI findings can stratify territorial collateral status and tissue fate.

Collateral Status in Ischemic Stroke: A Comparison of Computed Tomography Angiography, Computed Tomography Perfusion, and Digital Subtraction Angiography

OBJECTIVE

To compare assessment of collaterals by single-phase computed tomography (CT) angiography (CTA) and CT perfusion-derived 3-phase CTA, multiphase CTA and temporal maximum-intensity projection (tMIP) images to digital subtraction angiography (DSA), and relate collateral assessments to clinical outcome in patients with acute ischemic stroke.

METHODS

Consecutive acute ischemic stroke patients who underwent CT perfusion, CTA, and DSA before thrombectomy with occlusion of the internal carotid artery, the M1 or the M2 segments were included. Two observers assessed all CT images and one separate observer assessed DSA (reference standard) with static and dynamic (modified American Society of Interventional and Therapeutic Neuroradiology) collateral grading methods. Interobserver agreement and concordance were quantified with Cohen-weighted κ and concordance correlation coefficient, respectively. Imaging assessments were related to clinical outcome (modified Rankin Scale, ≤ 2).

RESULTS

Interobserver agreement (n = 101) was 0.46 (tMIP), 0.58 (3-phase CTA), 0.67 (multiphase CTA), and 0.69 (single-phase CTA) for static assessments and 0.52 (3-phase CTA) and 0.54 (multiphase CTA) for dynamic assessments. Concordance correlation coefficient (n = 80) was 0.08 (3-phase CTA), 0.09 (single-phase CTA), and 0.23 (multiphase CTA) for static assessments and 0.10 (3-phase CTA) and 0.27 (multiphase CTA) for dynamic assessments. Higher static collateral scores on multiphase CTA (odds ratio [OR], 1.7; 95% confidence interval [CI], 1.1-2.7) and tMIP images (OR, 2.0; 95% CI, 1.1-3.4) were associated with modified Rankin Scale of 2 or less as were higher modified American Society of Interventional and Therapeutic Neuroradiology scores on 3-phase CTA (OR, 1.5; 95% CI, 1.1-2.2) and multiphase CTA (OR, 1.7; 95% CI, 1.1-2.6).

CONCLUSIONS

Concordance between assessments on CT and DSA was poor. Collateral status evaluated on 3-phase CTA and multiphase CTA, but not on DSA, was associated with clinical outcome.

Intravenous Tissue Plasminogen Activator in Combination With Mechanical Thrombectomy: Clot Migration, Intracranial Bleeding, and the Impact of "Drip and Ship" on Effectiveness and Outcomes

Purpose: Intravenous tissue plasminogen activator (tPA) is indicated prior to mechanical thrombectomy (MT) to treat large vessel occlusion (LVO). However, administration takes time, and rates of clot migration complicating successful retrieval and hemorrhagic transformation may be higher. Given time-to-effectiveness, the benefit of tPA may vary significantly based on whether administration occurs at a thrombectomy-capable center or transferring hospital. Methods: We prospectively evaluated 170 individuals with LVO involving the anterior circulation who underwent MT at our Comprehensive Stroke Center over a 3.5 year period. Two thirds (n = 114) of patients were admitted through our Emergency Department (ED). The other 33% were transferred from outside hospitals (OSH). Patients meeting criteria were bridged with IV tPA; the others were treated with MT alone. Clot migration, recanalization times, TICI scores, and hemorrhage rates were compared for those bridged vs. treated with MT alone, along with modified Rankin scores (mRS) at discharge and 90-day follow-up. Multivariable regression was used to determine the relationship between site of presentation and effect of tPA on outcomes. Results: Patients presenting to an OSH had longer mean discovery to puncture/recanalization times, but were actually more likely to receive IV tPA prior to MT (70 vs. 42%). The rate of clot migration was low (11%) and similar between groups, though slightly higher for those receiving IV tPA. There was no difference in symptomatic ICH rate after tPA. TICI scores were also not significantly different; however, more patients achieved TICI 2b or higher reperfusion (83 vs. 67%, p = 0.027) after tPA, and TICI 0 reperfusion was seen almost exclusively in patients who were not treated with tPA. Those bridged at an OSH required fewer passes before successful recanalization (2.4 vs. 1.6, p = 0.037). Overall, mean mRS scores on discharge and at 90 days were significantly better for those receiving IV tPA (3.9 vs. 4.6, 3.4 vs. 4.4 respectively, p ~ 0.01) and differences persisted when comparing only patients recanalized in under 6 h. Conclusion: Independent of site of presentation, IV tPA before MT appears to lead to better radiographic outcomes, without increased rates of clot migration or higher intracranial hemorrhage risk, and overall better functional outcomes.

ColorViz, a New and Rapid Tool for Assessing Collateral Circulation during Stroke

Prognosis of patients with acute ischemic stroke is strictly related to the patency and prominence of the collateral leptomeningeal pathways distal to the arterial occlusion. The gold standard for assessment of collateral circulation is conventional angiography, but it is invasive and used in selected cases. To date, the most reliable technique is multiphase CTA; currently, the available classifications of collateral circles are often complex, time-consuming, and require a trained observer. The purpose of our work is to establish the effectiveness of a new semi-automatic post-processing software (ColorViz FastStroke, GE Healthcare, Milwaukee, Wisconsin) in evaluation of collateral circulation compared to the six-point classifications of multiphase CTA already validated in literature. We selected 86 patients with anterior ischemic stroke symptoms who underwent multiphasic CTA in our emergency department. Two radiologists separately evaluated the collateral leptomeningeal vessels, analyzing respectively, the multiphase CTA (using the six-point scale and its trichotomized form) and ColorViz (using a three-point scale). Then the results were matched. We found a good correlation between the two different analyses; the main advantage of ColorViz is that, while maintaining fast diagnostic times, it allows a simpler and more immediate evaluation of collateral circulation, especially for less experienced radiologists.

Arterial Spin Labeling MRI in Carotid Stenosis: Arterial Transit Artifacts May Predict Symptoms

BackgroundStenosis of the internal carotid artery has a higher risk for stroke. Many investigations have focused on structure and plaque composition as signs of plaque vulnerability, but few studies have analyzed hemodynamic changes in the brain as a risk factor.PurposeTo use 3-T MRI methods including contrast material-enhanced MR angiography, carotid plaque imaging, and arterial spin labeling (ASL) to identify imaging parameters that best help distinguish between asymptomatic and symptomatic participants with carotid stenosis.Materials and MethodsParticipants with carotid stenosis from two ongoing prospective studies who underwent ASL and carotid plaque imaging with use of 3-T MRI in the same setting from 2014 to 2018 were studied. Participants were assessed clinically for recent symptoms (transient ischemic attack or stroke) and divided equally into symptomatic and nonsymptomatic groups. Reviewers were blinded to the symptomatic status and MRI scans were analyzed for the degree of stenosis, plaque surface structure, presence of intraplaque hemorrhage (IPH), circle of Willis collaterals, and the presence and severity of arterial transit artifacts (ATAs) at ASL imaging. MRI findings were correlated with symptomatic status by using t tests and the Fisher exact test.ResultsA total of 44 participants (mean age, 71 years ± 10 [standard deviation]; 31 men) were evaluated. ATAs were seen only in participants with greater than 70% stenosis (16 of 28 patients; P < .001) and were associated with absence of anterior communicating artery (13 of 16 patients; P = .003). There was no association between history of symptoms and degree of stenosis (27 patients with ≥70% stenosis and 17 patients with <70%; P = .54), IPH (12 patients with IPH and 32 patients without IPH; P = .31), and plaque surface structure (17 patients with irregular or ulcerated plaque and 27 with smooth plaque; P = .54). Participants with ATAs (n = 16) were more likely to be symptomatic than were those without ATAs (n = 28) (P = .004). Symptomatic status also was associated with the severity of ATAs (P = .002).ConclusionArterial transit artifacts were the only factor associated with recent ischemic symptoms in participants with carotid stenosis. The degree of stenosis, plaque ulceration, and intraplaque hemorrhage were not associated with symptomatic status.© RSNA, 2020Online supplemental material is available for this article.See also the editorial by Zaharchuk in this issue.

Regional leptomeningeal collateral score by computed tomographic angiography correlates with 3-month clinical outcome in acute ischemic stroke

PURPOSE:

The aim of the study is to assess the correlation between regional leptomeningeal collateral (rLMC) Scores calculated on computed tomography (CT) angiography following acute anterior circulation ischemic stroke, with 3-month clinical outcome measured as modified Rankin Scale (mRS) and Barthel Index (BI).

MATERIALS AND METHODS:

A total of thirty patients were studied as per the exclusion and inclusion criteria and after informed consent. Multi-phase CT angiography was carried out within 24 h of stroke onset, and collateral scoring was done using rLMC score along with Alberta stroke programme early CT (ASPECT) scoring. At 3 months, patients were followed up to evaluate the clinical outcome using mRS and BI. Statistical analysis was performed to find out the correlation between rLMC score, ASPECT score, and clinical outcome and for association with demographic parameters and stroke risk factors.

RESULTS:

A strong correlation was noted between ASPECT and rLMC scores (P < 0.001) and between rLMC scores and clinical outcome at 3 months (mRS and BI). Correlation with mRS (P < 0.001) was nearly as strong as that of BI on follow-up (P < 0.001). The ASPECT score also was a predictor of clinical outcome and showed correlation with mRS (P < 0.001) and BI (P < 0.001). No significant association was found between various stroke risk factors and demographic parameters with rLMC scores. The rLMC scoring system showed substantial inter-rater reliability with Kappa = 0.7.

CONCLUSIONS:

rLMC score in CT angiography correlates with ASPECT Score and clinical outcome at 3 months. Hence, this scoring system can be used for collateral quantification as may be of use in predicting short-term clinical outcomes.

Revascularization Evaluation in Adult-Onset Moyamoya Disease after Bypass Surgery: Superselective Arterial Spin Labeling Perfusion MRI Compared with Digital Subtraction Angiography

Background A superselective (SS) arterial spin labeling (ASL) MRI technique can be used to monitor the revascularization area as a supplementary or alternative modality to digital subtraction angiography (DSA), with the advantage of being noninvasive. Purpose To evaluate whether SS-ASL perfusion MRI could be used to visualize the revascularization area after combined direct and indirect bypass surgery in adults with moyamoya disease compared with DSA. Materials and Methods Patients diagnosed with moyamoya disease who underwent DSA and SS-ASL 6 months after surgery between June 2017 and November 2019 in a single institution were retrospectively evaluated. Subjective grading of the revascularization area and collateral grading in 10 Alberta Stroke Program Early CT Score (ASPECTS) locations were performed. The change in perfusion status in a subgroup that underwent both preoperative and postoperative SS-ASL studies was evaluated. Intermodality agreement was analyzed by using weighted κ statistics. Results Thirty-seven hemispheres from 33 patients (mean age, 39 years ± 12 [standard deviation]; 20 women) were evaluated. The intermodality agreement of the revascularization area grading was substantial (weighted κ = 0.70; 95% confidence interval [CI]: 0.37, 1.00). The overall intermodality agreement of the postoperative collateral grading in the 10 ASPECTS locations for all vessels was substantial (weighted κ = 0.77; 95% CI: 0.74, 0.80). For the presence of postoperative collateral supplied by the ipsilateral external carotid artery in 10 ASPECTS locations (a total of 370 locations) using DSA as a reference test, the SS-ASL showed a sensitivity of 92% (183 of 199 locations; 95% CI: 87%, 95%) and a specificity of 83% (142 of 171 locations; 95% CI: 77%, 88%). The overall intermodality agreement of the changes in perfusion status was moderate (weighted κ = 0.59; 95% CI: 0.54, 0.65). Conclusion Superselective arterial spin labeling imaging precisely depicted the revascularization territory in patients with moyamoya disease who underwent bypass surgery, and it showed the changes in the vascular supplying territories before and after bypass surgery. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Hendrikse in this issue.

Prediction of long-term recurrent ischemic stroke: the added value of non-contrast CT, CT perfusion, and CT angiography

Purpose

The aim of this study was to evaluate whether the addition of brain CT imaging data to a model incorporating clinical risk factors improves prediction of ischemic stroke recurrence over 5 years of follow-up.

Methods

A total of 638 patients with ischemic stroke from three centers were selected from the Dutch acute stroke study (DUST). CT-derived candidate predictors included findings on non-contrast CT, CT perfusion, and CT angiography. Five-year follow-up data were extracted from medical records. We developed a multivariable Cox regression model containing clinical predictors and an extended model including CT-derived predictors by applying backward elimination. We calculated net reclassification improvement and integrated discrimination improvement indices. Discrimination was evaluated with the optimism-corrected c-statistic and calibration with a calibration plot.

Results

During 5 years of follow-up, 56 patients (9%) had a recurrence. The c-statistic of the clinical model, which contained male sex, history of hyperlipidemia, and history of stroke or transient ischemic attack, was 0.61. Compared with the clinical model, the extended model, which contained previous cerebral infarcts on non-contrast CT and Alberta Stroke Program Early CT score greater than 7 on mean transit time maps derived from CT perfusion, had higher discriminative performance (c-statistic 0.65, P = 0.01). Inclusion of these CT variables led to a significant improvement in reclassification measures, by using the net reclassification improvement and integrated discrimination improvement indices.

Conclusion

Data from CT imaging significantly improved the discriminatory performance and reclassification in predicting ischemic stroke recurrence beyond a model incorporating clinical risk factors only.

Electronic supplementary material

The online version of this article (10.1007/s00234-020-02526-5) contains supplementary material, which is available to authorized users.

Radiological predictors of hemorrhagic transformation after acute ischemic stroke: An evidence-based analysis

Hemorrhagic transformation (HT) is one of the most common adverse events related to acute ischemic stroke (AIS) that affects the treatment plan and clinical outcome. Identification of a sensitive radiological marker may influence the controversial thrombolytic decision in the setting of AIS and may at a minimum indicate more intensive monitoring or further prophylactic interventions. In this article we summarize possible radiological biomarkers and the role of different radiological modalities including computed tomography (CT), magnetic resonance imaging, angiography, and ultrasound in predicting HT. Different radiological indices of early ischemic changes, large ischemic lesion volume, severe blood flow restriction, blood-brain barrier disruption, poor collaterals and high blood flow velocities have been reported to be associated with higher risk of HT. The current levels of evidence of the available studies highlight the role of the different CT perfusion parameters in predicting HT. Further large standardized studies are recommended to compare the sensitivity and specificity of the different radiological markers combined and delineate the most reliable predictor.

Perfusion Quantification using Arterial Spin Labeling Magnetic Resonance Imaging after Revascularization for Moyamoya Disease

The hemodynamics in the brains of individuals with Moyamoya disease are complex and variable. Cerebral revascularization is an important treatment when hemodynamics are severely damaged. It's of great value to accurately quantify blood perfusion of different functional brain regions for better postoperative prognosis. In this study, we developed methods to segment territory of middle cerebral arteries (MCA) and its functional brain regions based on T1 and arterial spin labeling (ASL) imaging, absolute and normalized cerebral blood perfusion (CBF) were calculated for target regions-of-interest (ROI), spatial coefficient of variation was introduced to detect information of arterial transit time (ATT) contained in CBF images. After revascularization of Moyamoya disease, we detected perfusion improvement within MCA territory, while different alterations exist within different functional sub-regions. We also conformed that the spatial coefficient of variation of ASL CBF images can be used as an alternative ROI-based hemodynamic measurement to predict alterations of ATT. In summary, our methods show potential in postoperative evaluation of patients with Moyamoya disease.

Comparison of CBF Measured with Combined Velocity-Selective Arterial Spin-Labeling and Pulsed Arterial Spin-Labeling to Blood Flow Patterns Assessed by Conventional Angiography in Pediatric Moyamoya

BACKGROUND AND PURPOSE

Imaging CBF is important for managing pediatric moyamoya. Traditional arterial spin-labeling MR imaging detects delayed transit thorough diseased arteries but is inaccurate for measuring perfusion because of these delays. Velocity-selective arterial spin-labeling is insensitive to transit delay and well-suited for imaging Moyamoya perfusion. This study assesses the accuracy of a combined velocity-selective arterial spin-labeling and traditional pulsed arterial spin-labeling CBF approach in pediatric moyamoya, with comparison to blood flow patterns on conventional angiography.

MATERIALS AND METHODS

Twenty-two neurologically stable pediatric patients with moyamoya and 5 asymptomatic siblings without frank moyamoya were imaged with velocity-selective arterial spin-labeling, pulsed arterial spin-labeling, and DSA (patients). Qualitative comparison was performed, followed by a systematic comparison using ASPECTS-based scoring. Quantitative pulsed arterial spin-labeling CBF and velocity-selective arterial spin-labeling CBF for the middle cerebral artery, anterior cerebral artery, and posterior cerebral artery territories were also compared.

RESULTS

Qualitatively, velocity-selective arterial spin-labeling perfusion maps reflect the DSA parenchymal phase, regardless of postinjection timing. Conversely, pulsed arterial spin-labeling maps reflect the DSA appearance at postinjection times closer to the arterial spin-labeling postlabeling delay, regardless of vascular phase. ASPECTS comparison showed excellent agreement (88%, κ = 0.77, P < .001) between arterial spin-labeling and DSA, suggesting velocity-selective arterial spin-labeling and pulsed arterial spin-labeling capture key perfusion and transit delay information, respectively. CBF coefficient of variation, a marker of perfusion variability, was similar for velocity-selective arterial spin-labeling in patient regions of delayed-but-preserved perfusion compared to healthy asymptomatic sibling regions (coefficient of variation = 0.30 versus 0.26, respectively, Δcoefficient of variation = 0.04), but it was significantly different for pulsed arterial spin-labeling (coefficient of variation = 0.64 versus 0.34, Δcoefficient of variation = 0.30, P < .001).

CONCLUSIONS

Velocity-selective arterial spin-labeling offers a powerful approach to image perfusion in pediatric moyamoya due to transit delay insensitivity. Coupled with pulsed arterial spin-labeling for transit delay information, a volumetric MR imaging approach capturing key DSA information is introduced.

Multimodal CT in Acute Stroke

PURPOSE OF REVIEW

Multimodal CT imaging (non-contrast CT, NCCT; CT angiography, CTA; and CT Perfusion, CTP) is central to acute ischemic stroke diagnosis and treatment. We reviewed the purpose and interpretation of each component of multimodal CT, as well as the evidence for use in routine care.

RECENT FINDINGS

Acute stroke thrombolysis can be administered immediately following NCCT in acute ischemic stroke patients assessed within 4.5 h of symptom onset. Definitive identification of a large vessel occlusion (LVO) requires vascular imaging, which is easily achieved with CTA. This is critical, as the standard of care for LVO within 6 h of onset is now endovascular thrombectomy (EVT). CTA source images can also be used to estimate the efficacy of collateral flow in LVO patients. The final component (CTP) permits a more accurate assessment of the extent of the ischemic penumbra. Complete multimodal CT, including objective penumbral measurement with CTP, has been used to extend the EVT window to 24 h. There is also randomized controlled trial evidence for extension of the IV thrombolysis window to 9 h with multimodal CT. Although there have been attempts to assess for responders to reperfusion strategies beyond 6 h ("late window") using collateral grades, the only evidence for treatment of this group of patients is based on selection using multimodal CT including CTP. The development of fully automated software providing quantitative ischemic penumbral and core volumes has facilitated the adoption of CTP and complete multimodal CT into routine clinical use. Multimodal CT is a powerful imaging algorithm that is central to current ischemic stroke patient care.

Selection of anterior circulation acute stroke patients for mechanical thrombectomy

BACKGROUND

The use of mechanical thrombectomy (MT) for acute ischemic stroke (AIS) patients has increased with a parallel burden in procedural costs. We tested whether a new prognostic score could identify patients who are unlikely to benefit from MT.

METHODS

Patients from our endovascular stroke registry were assessed for imaging and clinical outcome measures and randomly divided into two subsets for derivation and validation. We created a new prognostic score based on clinical and radiological prognostic factors of poor outcome (mRS score ≥ 3) from the derivation cohort. Receiver operating characteristics curve analysis was used to assess the discrimination ability of the score. The score was then validated and compared to the MR PREDICTS score.

RESULTS

The derivation/validation included 270/116 patients, respectively. After multivariate logistic regression analysis, pre stroke mRS, age, admission glycaemia, admission NIHSS, collateral flow, Clot Burden Score, Alberta Stroke Program Early CT score were used to create a new prognostic scoring system called Tor Vergata Stroke Score (TVSS). TVSS revealed a good prognostic accuracy with an AUC of 0.825 [95% CI 0.77-0.88] in the derivation cohort and an AUC of 0.820 [95% CI 0.74-0.90] in the validation cohort. When compared to the MR PREDICTS in the validation cohort, TVSS demonstrated higher prediction ability which was, however, not statistically significant (0.80 vs 0.78; P = 0.26).

CONCLUSIONS

TVSS is a reliable tool for selection of AIS candidates for MT and optimization of transfer to comprehensive stroke centers.

Collaterals are a major determinant of the core but not the penumbra volume in acute ischemic stroke

PURPOSE

Determinants of early loss of ischemic tissue (core) or its prolonged survival (penumbra) in acute ischemic stroke (AIS) are poorly understood. We aimed to identify radiological associations of core and penumbra volumes on CT perfusion (CTP) in a large cohort of AIS.

METHODS

In the ASTRAL registry (2003-2016), we identified consecutive AIS patients with proximal middle cerebral artery (MCA) occlusion. We calculated core and penumbra volumes using established thresholds and the mismatch ratio (MR). We graded collaterals into three categories on CT-angiography. We used clot burden score (CBS) to quantify the clot length. We related CTP volumes to radiological variables in multivariate regression analyses, adjusted for time from stroke onset to first imaging.

RESULTS

The median age of the 415 included patients was 69 years (IQR = 21) and 49% were female. Median admission NIHSS was 16 (11) and median delay to imaging 2.2 h (1.9). Lower core volumes were associated with higher ASPECTS (hazard ratio = 1.08), absence of hyperdense MCA sign (HR = 0.70), higher CBS (i.e., smaller clot, HR = 1.10), and better collaterals (HR = 1.95). Higher penumbra volumes were related to lower CBS (i.e., longer clot, HR = 1.08) and proximal intracranial occlusion (HR = 1.47), but not to collaterals. Higher MR was found in absence of hyperdense MCA sign (HR = 1.28), absence of distal intracranial occlusion (HR = 1.39), and with better collaterals (HR = 0.52).

CONCLUSIONS

In AIS, better collaterals were associated with lower core volumes, but not with higher penumbra volumes. This suggests a major role of collaterals in early tissue loss and their limited significance as marker of salvageable tissue.

Simultaneous phase-contrast MRI and PET for noninvasive quantification of cerebral blood flow and reactivity in healthy subjects and patients with cerebrovascular disease

BACKGROUND

H₂ ¹⁵ O-positron emission tomography (PET) is considered the reference standard for absolute cerebral blood flow (CBF). However, this technique requires an arterial input function measured through continuous sampling of arterial blood, which is invasive and has limitations with tracer delay and dispersion.

PURPOSE

To demonstrate a new noninvasive method to quantify absolute CBF with a PET/MRI hybrid scanner. This blood-free approach, called PC-PET, takes the spatial CBF distribution from a static H₂ ¹⁵ O-PET scan, and scales it to the whole-brain average CBF value measured by simultaneous phase-contrast MRI.

STUDY TYPE

Observational.

SUBJECTS

Twelve healthy controls (HC) and 13 patients with Moyamoya disease (MM) as a model of chronic ischemic disease.

FIELD STRENGTH/SEQUENCES

3T/2D cardiac-gated phase-contrast MRI and H₂ ¹⁵ O-PET.

ASSESSMENT

PC-PET CBF values from whole brain (WB), gray matter (GM), and white matter (WM) in HCs were compared with literature values since 2000. CBF and cerebrovascular reactivity (CVR), which is defined as the percent CBF change between baseline and post-acetazolamide (vasodilator) scans, were measured by PC-PET in MM patients and HCs within cortical regions corresponding to major vascular territories. Statistical Tests: Linear, mixed effects models were created to compare CBF and CVR, respectively, between patients and controls, and between different degrees of stenosis.

RESULTS

The mean CBF values in WB, GM, and WM in HC were 42 ± 7 ml/100 g/min, 50 ± 7 ml/100 g/min, and 23 ± 3 ml/100 g/min, respectively, which agree well with literature values. Compared with normal regions (57 ± 23%), patients showed significantly decreased CVR in areas with mild/moderate stenosis (47 ± 17%, P = 0.011) and in severe/occluded areas (40 ± 16%, P = 0.016). Data Conclusion: PC-PET identifies differences in cerebrovascular reactivity between healthy controls and cerebrovascular patients. PC-PET is suitable for CBF measurement when arterial blood sampling is not accessible, and warrants comparison to fully quantitative H₂ ¹⁵ O-PET in future studies.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2020;51:183-194.

Preliminary application of CT perfusion source images for evaluating regional collateral circulation in unilateral Moyamoya disease

Background

Collateral flow is associated with clinical outcomes for patients with Moyamoya disease and served as a parameter for patient selection of therapeutic strategies. Therefore, we explored whether a noninvasive imaging modality, computed tomography perfusion (CTP) source images (CTP-Sis), could be used to identify the presence and intensity of collateral flow using digital subtraction angiography (DSA) as a gold standard for collateral flow.

Methods

CTP-Sis and DSA were performed for 24 patients with unilateral Moyamoya disease. A collateral grading system was developed based on arterial and venous phase CTP-Sis, imitating the DSA score system. Two neuroradiologists scored the DSA images using a collateral grading scale for the regions of interest corresponding to the Alberta Stroke Program Early computed tomography Score (ASPECTS) methodology. Another two neuroradiologists scored CTP-Sis in a similar manner. Agreement between the CTP-Sis and DSA consensus scores was determined, including kappa statistics.

Results

The agreement between the CTP-Sis and DSA consensus readings was moderate to strong, with a weighted kappa value of 0.768 [95% confidence interval (CI), 0.703-0.832], but there was a better agreement for readers of CTP-Sis, as compared with those of DSA. The sensitivity and specificity for identifying collaterals with CTP-Sis were 0.714 (95% CI, 0.578-0.851) and 0.995 (95% CI, 0.985-1.000), respectively.

Conclusions

CTP-Sis could help identify in a noninvasive manner the presence and intensity of collateral flow in patients with unilateral Moyamoya disease using DSA as a gold standard. Further study with a large number of cases is warranted. Further application of this method to other cerebrovascular diseases including acute ischemic stroke can also be warranted.

Cerebrovascular Reactivity Measured with ASL Perfusion MRI, Ivy Sign, and Regional Tissue Vascularization in Moyamoya

BACKGROUND

Arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) may be used to determine brain regions at risk for ischemia in patients with moyamoya vasculopathy and to identify patients who may benefit from surgical revascularization. We aimed to investigate whether 1) the severity of moyamoya is related to the presence of leptomeningeal collaterals and cerebrovascular reactivity (CVR), 2) the presence of collaterals and ivy sign reflects disturbed CVR, and 3) arterial transit artefacts (ATAs) and ivy sign reflect the presence of collaterals.

METHODS

We determined severity of moyamoya on digital subtraction angiography (DSA) according to the modified Suzuki classification in 20 brain regions and scored regional tissue revascularization using a 4-point scale. Regional CVR and ATAs were assessed on ASL perfusion MRI, ivy sign on fluid attenuation inversion recovery MRI.

RESULTS

In 11 patients (median age 36 years; 91% female), we studied 203 regions. ATAs were associated with the presence of collaterals on DSA (P < 0.01). Of all regions with clearly visible collateral vessels on DSA, however, only 24% had ATAs. Ivy sign was not related to the presence or absence of collaterals nor to CVR. In 10% of regions with good vascularization on DSA, CVR was poor or showed steal.

CONCLUSIONS

ATAs were associated with the presence of collaterals on DSA. Although DSA vascularization scores correlated with CVR, 10% of regions with good vascularization on DSA had absent CVR or steal on ASL-MRI. DSA and ivy sign did not provide adequate information on the hemodynamic status of brain tissue in patients with moyamoya vasculopathy.

Collateral perfusion using arterial spin labeling in symptomatic versus asymptomatic middle cerebral artery stenosis

The purpose was to assess the difference of collaterals in symptomatic versus asymptomatic patients with unilateral middle cerebral artery (MCA) stenosis by comparing cerebral blood flow (CBF) at two post labeling delays (PLD) using three-dimensional pseudo-continuous arterial spin labeling (3D pCASL). Eighty-one patients (49 symptomatic and 32 asymptomatic) with unilateral MCA stenosis ≥50% who underwent pCASL with two PLDs were included. Mean CBF and CBF subtraction images between two PLDs of MCA territories were compared in symptomatic and asymptomatic groups, respectively. Compared with the asymptomatic group, patients with symptomatic MCA stenosis had significantly lower CBF in the MCA territory of stenotic side at each PLD. The CBF of stenotic territory showed greater increase than that of normal side from PLD 1.5 to 2.5 s. The CBF of asymptomatic MCA territory increased similarly with that of symptomatic MCA territory from PLD of 1.5 to 2.5 s in stenotic side, while symptomatic patients experienced significantly slower antegrade flow. On CBF subtraction images, asymptomatic patients showed larger volume of differences between PLD of 1.5 and 2.5 s compared with those of symptomatic patients ( p = 0.037). The results suggest that more robust collateral perfusion on two-delay 3D pCASL is present in asymptomatic patients compared with symptomatic patients.

Influence of the circle of Willis on leptomeningeal collateral flow in anterior circulation occlusive stroke: Friend or foe?

BACKGROUND

Clinical outcome after large vessel occlusion (LVO) stroke depends on collateral integrity. We aimed to evaluate whether the completeness of the circle of Willis (CoW) and anterior temporal artery (ATA) determines the status of leptomeningeal collaterals (LC) in patients with acute LVO (internal carotid artery (ICA) and middle cerebral artery M1 (MCA) occlusion) treated with endovascular thrombectomy.

PATIENTS AND METHODS

LC, cross-flow through the anterior communicating artery (ACoA), presence of the ipsilateral posterior communicating artery (IpsiPCoA) and presence of the ATA were evaluated using CT angiography. LC was graded as good when ≥50% collateral filling was noted compared to the unaffected hemisphere.

RESULTS

We included 159 patients with a median age of 75 years (IQR 63-82), MCA M1 occlusion in 96 (60%) and good outcome in 68 (45.6%). The LC were good in 129 (81.1%) patients. Complete IpsiPCoA and incomplete ACoA status was inversely associated with good LC in LVO (OR 0.51 (95% CI 0.02-0.07)). A complete CoW was associated with good LC in ICA occlusions, OR 8.4 (p = .025). Good outcome (modified Rankin scale 0-2 at 3 months) was associated with good LC (OR 5.63 (95% CI 1.11-28.4)), small ischemic lesion volume (OR 0.94 (95% CI 0.97-0.98)) and absence of the ACoA and IpsiPCoA (OR 4.47 (95% CI 1.09-18.3)).

CONCLUSIONS

ATA presence was associated with good leptomeningeal collaterals in LVO (OR 8.13 (95% CI 1.69-39.0)) and in MCA M1 patients (OR 7.9 (95% CI 1.7-36.4)). The effect of ATA was most pronounced in MCA M1 occlusions, and that of ACoA was most pronounced in ICA occlusions.

Patterns of Stroke Transfers and Identification of Predictors for Thrombectomy

BACKGROUND

Interhospital transfers for endovascular thrombectomy (EVT) evaluation have increased since the publication of landmark neuroendovascular stroke trials in 2015. The lack of guidelines to select potential EVT candidates prior to transfer can lead to instances where, despite considerable costs and transport risks, transferred patients do not ultimately undergo EVT. Our aim was to characterize the patterns and identify predictors for EVT on transfer.

METHODS

In this observational cohort study, we retrospectively analyzed patients with acute ischemic stroke (AIS) transferred to our institution for EVT evaluation from January 2015 to March 2016. Clinical and radiographic predictors for EVT on transfer were determined with multivariable logistic regression analysis.

RESULTS

A total of 103 transfer patients with AIS were included in the study, and 52% were women. A higher collateral score (P < 0.01), a higher National Institutes of Health Stroke Scale (NIHSS) score (P < 0.01), computed tomography angiography (CTA) at referring hospital (P < 0.01), and large vessel occlusion on arrival CTA (P < 0.01) were significant in patients who underwent EVT on univariable analysis. More than half (61.1%) of transfers were futile and primarily related to absence of large vessel occlusion on arrival. A higher collateral score (P = 0.02), a higher NIHSS score (P = 0.006), and having undergone a CTA at the referring center (P = 0.002) remained the independent predictors of EVT. The C statistic for the model was 0.94.

CONCLUSIONS

A higher collateral score, the acquisition of CTA imaging at the referring centers, and a higher NIHSS score independently predicted EVT on transfer.

Higher admission fasting plasma glucose levels are associated with a poorer short-term neurologic outcome in acute ischemic stroke patients with good collateral circulation

AIMS

In this retrospective study, we sought to delineate the collateral circulation status of acute ischemic stroke patients by CT perfusion and evaluate 90-day modified Rankin Scale (mRS) scores of patients with good or poor collaterals and its correlation with admission fasting plasma glucose (FPG).

METHODS

We enrolled acute ischemic stroke patients who presented to our hospital 4.5 h within an onset of the first episode between January 2009 and December 2015. Neurological assessment was performed using the 90-day mRS scores (0-2 for a favorable and 3-6 for an unfavorable neurologic outcome). Relative filling time delay (rFTD) was evaluated by CT perfusion scan. The primary outcomes were 90-day mRS scores stratified by good (rFTD ≤ 4 s) versus poor collateral circulation (rFTD > 4 s).

RESULTS

Totally 270 patients were included, and 139 (51.5%) patients achieved a favorable neurologic outcome. One hundred eighty-five (68.5%) patients had good collateral circulation. Significantly greater portions of patients with good collateral circulation (60.5%, 112/185) achieved a favorable neurologic outcome compared to those with poor collateral circulation (31.8%, 27/85) (P < 0.05). Patients with good collateral circulation achieving a favorable neurologic outcome had significantly lower baseline FPG (6.6 ± 1.96) than those with good collateral circulation achieving an unfavorable neurologic outcome (8.12 ± 4.02; P = 0.002). Spearman correlation analysis showed that rFTD significantly correlated with 90-day mRS scores (adjusted r = 0.258; P < 0.001) and admission FPG (r = 0.286; P < 0.001).

CONCLUSION

Higher admission FPG levels are associated with significantly higher rates of unfavorable neurologic outcome of acute ischemic stroke patients with good collateral circulation. FPG and rFTD may serve as useful predictors of short-term patient outcome and could be used for risk stratification in clinical decision making.

Monitoring Cerebral Perfusion Changes after Revascularization in Patients with Moyamoya Disease by Using Arterial Spin-labeling MR Imaging

Purpose To determine whether arterial spin-labeling (ASL) magnetic resonance (MR) imaging could be used to identify changes in cerebral blood flow (CBF), collateral blood flow, and anastomosis site patency after revascularization in patients with moyamoya disease. Materials and Methods This retrospective study was conducted in 145 patients with moyamoya disease who underwent middle cerebral artery (MCA)-superficial temporal artery anastomosis. Preoperative, early postoperative, and late postoperative ASL and digital subtraction angiography images were analyzed. In the MCA territory, absolute CBF (hereafter, CBF_MCA) and normalized CBF values adjusted to nonanastomosis side (hereafter, nCBF_MCA) and to cerebellum (hereafter, nCBF_Cbll) were calculated. Collateral grading in the MCA territory was assessed according to Alberta Stroke Program Early CT Score methodology, and anastomosis site patency were also assessed. Changes in CBF were compared by using one-way analysis of variance with Bonferroni correction for multiple comparisons. Intermodality agreement was determined by κ statistics. Results Significant increases in CBF_MCA, nCBF_MCA, and nCBF_Cbll were found after revascularization (preoperative and postoperative values of CBF_MCA, 35.2 mL/100 g per minute ± 7.8 [mean ± standard deviation] and 51.5 mL/100 g per minute ± 12.0; nCBF_MCA, 0.73 mL/100 g per minute ± 0.14 and 1.01 mL/100 g per minute ± 0.18; nCBF_Cbll, 0.74 mL/100 g per minute ± 0.12 and 1.12 mL/100 g per minute ± 0.16; all P < .001). Agreements for collateral grading and anastomosis patency between ASL MR imaging and digital subtraction angiography were moderate to good, with weighted κ values of 0.77 (95% confidence interval: 0.73, 0.81) and 0.57 (95% confidence interval: 0.37, 0.76), respectively. Conclusion ASL MR imaging can be used to identify perfusion changes in patients with moyamoya disease after revascularization as a noninvasive monitoring tool.

Comparison of Blood Oxygenation Level-Dependent fMRI and Provocative DSC Perfusion MR Imaging for Monitoring Cerebrovascular Reserve in Intracranial Chronic Cerebrovascular Disease

BACKGROUND AND PURPOSE

Loss of hemodynamic reserve in intracranial cerebrovascular disease reduces blood oxygenation level-dependent activation by fMRI and increases asymmetry in MTT measured by provocative DSC perfusion MR imaging before and after vasodilation with intravenous acetazolamide. The concordance for detecting hemodynamic reserve integrity has been compared.

MATERIALS AND METHODS

Patients (n = 40) with intracranial cerebrovascular disease and technically adequate DSA, fMRI and provocative DSC perfusion studies were retrospectively grouped into single vessels proximal to and distal from the circle of Willis, multiple vessels, and Moyamoya disease. The vascular territories were classified as having compromised hemodynamic reserve if the expected fMRI blood oxygenation level-dependent activation was absent or if MTT showed increased asymmetry following vasodilation. Concordance was examined in compromised and uncompromised vascular territories of each group with the Fischer exact test and proportions of agreement.

RESULTS

Extensive leptomeningeal collateral circulation was present in all cases. Decreased concordance between the methods was found in vascular territories with stenosis distal to but not proximal to the circle of Willis. Multivessel and Moyamoya diseases also showed low concordance. A model of multiple temporally displaced arterial inputs from leptomeningeal collateral flow demonstrated that the resultant lengthening MTT mimicked compromised hemodynamic reserve despite being sufficient to support blood oxygenation level-dependent contrast.

CONCLUSIONS

Decreased concordance between the 2 methods for assessment of hemodynamic reserve for vascular disease distal to the circle of Willis is posited to be due to well-developed leptomeningeal collateral circulation providing multiple temporally displaced arterial input functions that bias the perfusion analysis toward hemodynamic reserve compromise while blood oxygenation level-dependent activation remains detectable.

Long-Delay Arterial Spin Labeling Provides More Accurate Cerebral Blood Flow Measurements in Moyamoya Patients: A Simultaneous Positron Emission Tomography/MRI Study

BACKGROUND AND PURPOSE

Arterial spin labeling (ASL) MRI is a promising, noninvasive technique to image cerebral blood flow (CBF) but is difficult to use in cerebrovascular patients with abnormal, long arterial transit times through collateral pathways. To be clinically adopted, ASL must first be optimized and validated against a reference standard in these challenging patient cases.

METHODS

We compared standard-delay ASL (post-label delay=2.025 seconds), multidelay ASL (post-label delay=0.7-3.0 seconds), and long-label long-delay ASL acquisitions (post-label delay=4.0 seconds) against simultaneous [¹⁵O]-positron emission tomography (PET) CBF maps in 15 Moyamoya patients on a hybrid PET/MRI scanner. Dynamic susceptibility contrast was performed in each patient to identify areas of mild, moderate, and severe time-to-maximum (Tmax) delays. Relative CBF measurements by each ASL scan in 20 cortical regions were compared with the PET reference standard, and correlations were calculated for areas with moderate and severe Tmax delays.

RESULTS

Standard-delay ASL underestimated relative CBF by 20% in areas of severe Tmax delays, particularly in anterior and middle territories commonly affected by Moyamoya disease (P<0.001). Arterial transit times correction by multidelay acquisitions led to improved consistency with PET, but still underestimated CBF in the presence of long transit delays (P=0.02). Long-label long-delay ASL scans showed the strongest correlation relative to PET, and there was no difference in mean relative CBF between the modalities, even in areas of severe delays.

CONCLUSIONS

Post-label delay times of ≥4 seconds are needed and may be combined with multidelay strategies for robust ASL assessment of CBF in Moyamoya disease.

Feline Cardiogenic Arterial Thromboembolism: Prevention and Therapy

Feline cardiogenic arterial thromboembolism (CATE) is a devastating disease whereby 33% of cats survive their initial event, although approximately 50% of mortality is from euthanasia. Short-term management focuses on inducing a hypocoagulable state, improving blood flow, and providing supportive care. Ideally, all cats should be given 72 hours of treatment to determine the acute clinical course. Preventive protocols include antiplatelet and/or anticoagulant drugs, with the only prospective clinical trial demonstrating that clopidogrel is superior to aspirin with a lower CATE recurrence rate and longer time to recurrent CATE. Newer anticoagulant drugs hold great promise in the future of managing this disease.

Regional Comparison of Multiphase Computed Tomographic Angiography and Computed Tomographic Perfusion for Prediction of Tissue Fate in Ischemic Stroke

BACKGROUND AND PURPOSE

Within different brain regions, we determine the comparative value of multiphase computed tomographic angiography (mCTA) and computed tomographic perfusion (CTP) in predicting follow-up infarction.

METHODS

Patients with M1-middle cerebral artery occlusions were prospectively included in this multicenter study. Regional analysis was performed for each patient within Alberta Stroke Program Early CT Score regions M2 to M6. Regional pial vessel filling was assessed on mCTA in 3 ways: (1) Washout of contrast within pial vessels; (2) Extent of maximal pial vessel enhancement compared with contralateral hemisphere; (3) Delay in maximal pial vessel enhancement compared with contralateral hemisphere. Cerebral blood flow, cerebral blood volume, and Tmax data were extracted within these Alberta Stroke Program Early CT Score regions. Twenty-four- to 36-hour magnetic resonance imaging/CT was assessed for infarct in each Alberta Stroke Program Early CT Score region (defined as >20% infarction within that region). Mixed effects logistic regression models were used to compare mCTA and CTP parameters when predicting brain infarction. Area under the receiver operating characteristics was used to assess discriminative value of statistical models.

RESULTS

Seventy-seven patients were included. mCTA parameter washout and CTP parameter Tmax were significantly associated with follow-up infarction in all models (P<0.05). The area under the receiver operating characteristic for mCTA models ranged from 92% to 94% and was not different compared with all CTP models (P>0.05). Mean Tmax and cerebral blood volume values were significantly different between each washout score (P<0.01) and each delay score category (P<0.01). Mean Tmax, cerebral blood flow, and cerebral blood volume values were significantly different between each extent score category (P<0.05).

CONCLUSIONS

Similar to CTP, multiphase CTA can be used to predict tissue fate regionally in acute ischemic stroke patients.

Prediction of Blood–Brain Barrier Disruption and Intracerebral Hemorrhagic Infarction Using Arterial Spin-Labeling Magnetic Resonance Imaging

Background and Purpose—

Arterial spin-labeling magnetic resonance imaging is sensitive for detecting hyperemic lesions (HLs) in patients with acute ischemic stroke. We evaluated whether HLs could predict blood–brain barrier (BBB) disruption and hemorrhagic transformation (HT) in acute ischemic stroke patients.

Methods—

In a retrospective study, arterial spin-labeling was performed within 6 hours of symptom onset before revascularization treatment in 25 patients with anterior circulation large vessel occlusion on baseline magnetic resonance angiography. All patients underwent angiographic procedures intended for endovascular therapy and a noncontrast computed tomography scan immediately after treatment. BBB disruption was defined as a hyperdense lesion present on the posttreatment computed tomography scan. A subacute magnetic resonance imaging or computed tomography scan was performed during the subacute phase to assess HTs. The relationship between HLs and BBB disruption and HT was examined using the Alberta Stroke Program Early Computed Tomography Score locations in the symptomatic hemispheres.

Results—

A HL was defined as a region where CBF relative ≥1.4 (CBF relative =CBF HL /CBF contralateral ). HLs, BBB disruption, and HT were found in 9, 15, and 15 patients, respectively. Compared with the patients without HLs, the patients with HLs had a higher incidence of both BBB disruption (100% versus 37.5%; P =0.003) and HT (100% versus 37.5%; P =0.003). Based on the Alberta Stroke Program Early Computed Tomography Score locations, 21 regions of interests displayed HLs. Compared with the regions of interests without HLs, the regions of interests with HLs had a higher incidence of both BBB disruption (42.8% versus 3.9%; P <0.001) and HT (85.7% versus 7.8%; P <0.001).

Conclusions—

HLs detected on pretreatment arterial spin-labeling maps may enable the prediction and localization of subsequent BBB disruption and HT.

Permeability Imaging as a Biomarker of Leptomeningeal Collateral Flow in Patients with Intracranial Arterial Stenosis

Different methods of angiography are of great clinical utility; however, it still remains unstandardized as which method would be suitable to determine cerebral collateral circulation. Here we compared digital subtraction angiography (DSA), computer tomography angiography (CTA) and dynamic contrast-enhanced T1-weighted imaging magnetic resonance imaging (MRI) findings in seven patients with severe intracranial arterial stenosis, and determine whether volume transfer constant (K(trans)) maps of permeability imaging could be used as the biomarkers of cerebral collateral circulation. We retrospectively reviewed seven adult patients with severe intracranial arterial stenosis or occlusion with a complete parenchymal and vascular imaging work-up. DSA, CTA source imaging (CTA-SI), arterial spin labeling (ASL), and K(trans) maps were used to assess their collateral flow. Cohen's Kappa coefficient was calculated to test the consistency of their collateral scores. A reasonable agreement was found between DSA and K(trans) maps (Kappa = 0.502, P < 0.001) when all 15 regional vascular sites were included, and a better agreement found after exclusion of perforating artery territories (N = 10 sites, Kappa = 0.766, P < 0.001). The agreement between CTA-SI and DSA was moderate on all 15 sites (Kappa = 0.413, P < 0.001) and 10 sites (Kappa = 0.329, P < 0.001). The agreement between ASL and DSA was least favorable, no matter for all 15 sites (Kappa = 0.270, P < 0.001) or 10 sites (Kappa = 0.205, P = 0.002). K(trans) maps are useful and promising for leptomeningeal collateral assessment, when compared to CTA-SI or ASL. Further studies are requited for verify its validity in a large registry of patients.

Cerebral blood flow, transit time, and apparent diffusion coefficient in moyamoya disease before and after acetazolamide

INTRODUCTION

The goal of this study was to assess the changes in arterial spin labeling (ASL) cerebral blood flow (CBF) and arterial transit time (ATT), and in apparent diffusion coefficient (ADC), before and after an acetazolamide challenge in moyamoya patients, as function of arterial stenosis severity.

METHODS

Pre-operative patients diagnosed with moyamoya disease who could undergo MRI at 3.0T were recruited for this study. A multi-delay pseudo-continuous ASL and a diffusion-weighted sequence were acquired before and 15 min after acetazolamide injection. The severity of anterior, middle, and posterior cerebral artery pathology was graded on time-of-flight MR angiographic images. CBF, ATT, and ADC were measured on standardized regions of interest as function of the vessel stenosis severity.

RESULTS

Thirty patients were included. Fifty-four percent of all vessels were normal, 28% mildly/moderately stenosed, and 18% severely stenosed/occluded. Post-acetazolamide, a significantly larger CBF (ml/100 g/min) increase was observed in territories of normal (+19.6 ± 14.9) compared to mildly/moderately stenosed (+14.2 ± 27.2, p = 0.007), and severely stenosed/occluded arteries (+9.9 ± 24.2, p < 0.0001). ATT was longer in territories of vessel anomalies compared with normal regions at baseline. ATT decreases were observed in all territories post-acetazolamide. ADC did not decrease after acetazolamide in any regions, and no correlation was found between ADC changes and baseline ATT, change in ATT, or CVR.

CONCLUSION

The hemodynamic response in moyamoya disease, as measured with ASL CBF, is impaired mostly in territories with severe arterial stenosis/occlusion, while ATT was prolonged in all non-normal regions. No significant changes in ADC were observed after acetazolamide.

Assessment of cerebrovascular reserve in unilateral middle cerebral artery stenosis using perfusion CT and CO2 inhalation tests

Purpose/Aim of the study: Cerebrovascular reactivity (CVR) is an important marker for assessing cerebrovascular disease. This study assessed the CVR by perfusion computed tomography (CT) and CO₂ inhalation tests in patients with unilateral middle cerebral artery (MCA) stenosis disease.

MATERIALS AND METHODS

Thirty-one patients with unilateral MCA stenosis disease diagnosed by digital subtraction angiography were studied. Patients were divided into two groups according to the degree of stenosis: severe and moderate. The regional cerebral blood flow (CBF) before and after CO₂ inhalation was determined by perfusion CT. Regional CVR values were obtained by the following formula: increase (%) = (post-CBF) - (pre-CBF)/(pre-CBF) × 100%.

RESULTS

No significant differences in the mean CBF in the MCA stenosis region were found between the affected and contralateral sides before the CO₂ inhalation test; after the test, CBF was more significantly decreased on the affected side than on the contralateral side. The changes in CBF on the affected side were categorized into three types: increased CBF (17 cases), decreased CBF (12 cases) and no change in CBF (2 cases). The rate of CVR impairment among severe stenosis patients (13/19) was higher than that among moderate stenosis patients (3/12). CVR was significantly correlated with the degree of stenosis (r = 0.423, P = 0.018).

CONCLUSION

CVR impairment was found in approximately half of patients with unilateral MCA stenosis. Along with an increase in the degree of stenosis, patients with unilateral MCA stenosis were more likely to exhibit CVR impairment. It is important to assess the CVR in patients with unilateral MCA stenosis, especially those with severe stenosis.