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The interval appearance of cerebral microbleeds (CMBs) after endovascular treatment has never been described. We investigated the frequency and predictors of new CMBs that developed shortly after mechanical thrombectomy for acute ischemic stroke, and its impact on clinical outcome.We retrospectively analyzed patients with large-vessel occlusion strokes treated with Merci Retriever, Penumbra System, or stent-retriever devices. Serial T2*-weighted gradient-recall echo (GRE) magnetic resonance imaging (MRI) before and 48 h after endovascular thrombectomy were assessed to identify new CMBs. We examined independent factors associated with new CMBs after mechanical thrombectomy. We analyzed the association of the presence, burden, and distribution of new CMBs with clinical outcome.A total of 187 consecutive patients with serial GRE were enrolled in this study. CMBs were evident in 36 (19.3%) patients before mechanical thrombectomy. New CMBs occurred in 41 (21.9%) patients after mechanical thrombectomy. Of the 68 new CMBs, 45 appeared in the lobar location, 18 in the deep location and 5 in the infratentorial location. The presence of baseline CMBs was associated with new CMBs after mechanical thrombectomy (OR 5.38; 95% CI 2.13-13.59; P < 0.001), no matter whether the patients were treated primarily with mechanical thrombectomy or with intravenous thrombolysis followed by mechanical thrombectomy. Patients with new CMBs did not have increased rates of hemorrhagic transformation, in-hospital mortality, and modified Rankin Scale score 4 to 6 at discharge.New CMBs are common after mechanical thrombectomy in one-fifth of patients with acute ischemic stroke. Baseline CMBs before mechanical thrombectomy predicts the development of new CMBs. New CMBs after mechanical thrombectomy do not influence clinical outcome., Competing Interests: The authors have no conflicts of interest to disclose.

Background and Purpose: The purpose of this study was to determine whether leukoaraiosis (LA) predicts hemorrhagic transformation and poor outcome in patients with acute ischemic stroke treated by mechanical thrombectomy., Methods: We retrospectively analyzed patients with anterior circulation stroke treated with Merci devices and identified LA in the deep white matter (DWM) and periventricular white matter on the preintervention MR images. We dichotomized patients into those with moderate or severe LA in the DWM versus those without. Hemorrhage rates and outcomes were evaluated between 2 groups. We analyzed the association of moderate or severe LA with hemorrhagic transformation and poor outcome., Results: Twenty-six of 105 patients had moderate or severe LA in the DWM. Patients with moderate or severe LA in the DWM were older, had more severe neurological deficits and worse outcome, had higher rates of hemorrhagic transformation and parenchymal hematoma, but had equivalent rates of hemorrhagic infarct and subarachnoid hemorrhage when compared with those without. Patients with only periventricular LA did not have a higher rate of parenchymal hematoma. Moderate or severe LA in the DWM was an independent predictor of hemorrhagic transformation (OR, 3.4; P=0.019) and parenchymal hematoma (OR, 6.3; P=0.005). Patients with parenchymal hematoma were less often independent (modified Rankin Scale≤2, 3.8% versus 32.5%; P=0.003) and had greater in-hospital mortality (50% versus 10.4%; P<0.001)., Conclusions: Moderate or severe LA in the DWM increases the risk of parenchymal hematoma after Merci thrombectomy for patients with acute stroke. These findings require validation in a larger prospective study.

Background and Purpose: The purpose of this study was to evaluate the potential clinical value of arterial spin-labeled (ASL) perfusion MRI in acute ischemic stroke (AIS) through comparison with dynamic susceptibility contrast (DSC) enhanced perfusion MRI., Methods: Pseudocontinuous ASL with 3-dimensional background-suppressed gradient and spin echo readout was applied with DSC perfusion MRI on 26 patients with AIS. ASL cerebral blood flow and multiparametric DSC perfusion maps were rated for image quality and lesion severity/conspicuity. Mean ASL cerebral blood flow and DSC perfusion values were obtained in main vascular territories. Kendall coefficient of concordance was calculated to evaluate the reliability of ratings. Spearman correlation coefficients were calculated to compare ratings and quantitative perfusion values between ASL and DSC perfusion maps., Results: ASL cerebral blood flow and DSC perfusion maps provided largely consistent results in delineating hypoperfused brain regions in AIS. Hyperemic lesions, which also appeared frequently in the AIS cases studied, were more conspicuous on ASL cerebral blood flow than on DSC cerebral blood flow, mean transit time and time to the maximum of the tissue residual function maps., Conclusions: As a rapid, noninvasive, and quantitative technique, ASL has clinical use in detecting blood flow abnormalities in patients with AIS.

Background and Purpose: Determinants of successful recanalization likely differ for Merci thrombectomy and intra-arterial pharmacological fibrinolysis interventions. Although the amount of thrombotic material to be digested is an important consideration for chemical lysis, mechanical debulking may be more greatly influenced by other target lesion characteristics., Methods: In consecutive patients with acute ischemic stroke treated with Merci thrombectomy for middle cerebral artery M1 occlusions, we analyzed the influence on recanalization success and clinical outcome of target thrombus size (length) and shape (curvature and branching) on pretreatment T2* gradient echo MRI., Results: Among 65 patients, pretreatment MRI showed susceptibility vessel signs in 45 (69%). Thrombus length averaged 13.03 mm (range, 5.56-34.91) and irregular shape (curvature or branching) was present in 17 of 45 (38%). Presence and length of susceptibility vessel signs did not predict recanalization or good clinical outcome. Substantial recanalization (Thrombolysis In Cerebral Infarction 2b or 3) and good clinical outcome (modified Rankin Scale score ≤2) were more frequent with regular than irregular susceptibility vessel signs shape (57% versus 18%, P=0.013; 39% versus 6%, P=0.017). On multiple regression analysis, the only independent predictor of substantial recanalization was irregular susceptibility vessel signs (OR, 0.16; 95% CI, 0.04-0.69; P=0.014); and leading predictors of good clinical outcome were baseline National Institutes of Health Stroke Scale (OR, 1.20; 95% CI, 1.03-1.40; P= 0.019) and irregular susceptibility vessel signs (OR, 9.36; 95% CI, 0.98-89.4; P=0.052)., Conclusions: Extension of thrombus into middle cerebral artery division branches and curving shape of the middle cerebral artery stem, but not thrombus length, decrease technical and clinical success of Merci thrombectomy in M1 occlusions.

Background and Purpose: The purpose of this study was to provide the first correlative study of the hyperdense middle cerebral artery sign (HMCAS) and gradient-echo MRI blooming artifact (BA) with pathology of retrieved thrombi in acute ischemic stroke., Methods: Noncontrast CT and gradient-echo MRI studies before mechanical thrombectomy in 50 consecutive cases of acute middle cerebral artery ischemic stroke were reviewed blinded to clinical and pathology data. Occlusions retrieved by thrombectomy underwent histopathologic analysis, including automated quantitative and qualitative rating of proportion composed of red blood cells (RBCs), white blood cells, and fibrin on microscopy of sectioned thrombi., Results: Among 50 patients, mean age was 66 years and 48% were female. Mean (SD) proportion was 61% (±21) fibrin, 34% (±21) RBCs, and 4% (±2) white blood cells. Of retrieved clots, 22 (44%) were fibrin-dominant, 13 (26%) RBC-dominant, and 15 (30%) mixed. HMCAS was identified in 10 of 20 middle cerebral artery stroke cases with CT with mean Hounsfield Unit density of 61 (±8 SD). BA occurred in 17 of 32 with gradient-echo MRI. HMCAS was more commonly seen with RBC-dominant and mixed than fibrin-dominant clots (100% versus 67% versus 20%, P=0.016). Mean percent RBC composition was higher in clots associated with HMCAS (47% versus 22%, P=0.016). BA was more common in RBC-dominant and mixed clots compared with fibrin-dominant clots (100% versus 63% versus 25%, P=0.002). Mean percent RBC was greater with BA (42% versus 23%, P=0.011)., Conclusions: CT HMCAS and gradient-echo MRI BA reflect pathology of occlusive thrombus. RBC content determines appearance of HMCAS and BA, whereas absence of HMCAS or BA may indicate fibrin-predominant occlusive thrombi.

Background and Purpose: Few data exist on the relationship between differential subpopulations of peripheral leukocytes and early cerebral infarct size in ischemic stroke. Using diffusion-weighted MR imaging (DWI), we assessed the relationship of early total and differential peripheral leukocyte counts and volume of ischemic tissue in acute stroke., Methods: All included patents had laboratory investigations and neuroimaging collected within 24 hours of stroke onset. Total peripheral leukocyte counts and differential counts were analyzed individually and by quartiles. DWI lesions were outlined using a semiautomated threshold technique. The relationship between leukocyte quartiles and DWI infarct volumes was examined using multivariate quartile regression., Results: 173 patients met study inclusion criteria. Median age was 73 years. Total leukocyte counts and DWI volumes showed a strong correlation (Spearman rho=0.371, P<000.1). Median DWI volumes (mL) for successive neutrophil quartiles were: 1.3, 1.3, 3.2, and 20.4 (P for trend <0.001). Median DWI volumes (mL) for successive lymphocyte quartiles were: 3.2, 8.1, 1.3, and 1.5 (P=0.004). After multivariate analysis, larger DWI volume remained strongly associated with higher total leukocyte and neutrophil counts (both probability values <0.001), but not with lymphocyte count (P=0.4971). Compared with the lowest quartiles, DWI volumes were 8.7 mL and 12.9 mL larger in the highest quartiles of leukocyte and neutrophil counts, respectively., Conclusions: Higher peripheral leukocyte and neutrophil counts, but not lymphocyte counts, are associated with larger infarct volumes in acute ischemic stroke. Attenuating neutrophilic response early after ischemic stroke may be a viable therapeutic strategy and warrants further study.

Objective: The objective of this study was to evaluate a high spatial resolution 3-dimensional (3D) contrast-enhanced magnetic resonance (CE-MR) venography protocol for evaluation of intracranial venous system using highly accelerated parallel imaging at 3.0 T., Materials and Methods: Ten patients (4 male, 6 female; age, 38-76 years) with suspected cerebrovascular disease were prospectively studied on a 32-channel 3.0 T MR system. After a single intravenous contrast injection, high spatial resolution 3D CE-MR angiography of the entire supraaortic arteries was performed followed immediately by 3D cerebral CE-MR venography. By using a fast 3D gradient-recalled-echo sequence with elliptic centric k-space ordering and highly accelerated parallel acquisition (acceleration factor 3 and 2 in phase and slice encoding direction, respectively), 3D cerebral CE-MR venography was acquired with voxel dimensions of 0.7 x 0.7 x 0.8 mm in 24 seconds. Image evaluation was performed independently by 2 neuroradiologists for overall image quality, presence of noise, and artifacts. The image quality of 30 venous segments was evaluated in each subject using a 1 to 4 scoring scale. In 2 patients, catheter angiography was available for correlation. Statistical analysis of data was performed by using Wilcoxon rank sum test and kappa coefficient., Results: All studies were determined to be of diagnostic image quality by both observers. The majority (90%) of cerebral venous segments were evaluated to be of diagnostic image quality (median, 3; range, 3-4) by both readers and with excellent interobserver agreement (kappa = 0.86; 95% confidence interval, 0.79-0.93). One meningioma invading the superior sagittal sinus and one superior sagittal sinus fistula were detected subsequently confirmed by conventional angiography., Conclusion: High spatial resolution 3D cerebral CE-MR venography is feasible and promising. Using a 32-channel 3.0 T system combined with multichannel array coils effectively supports highly accelerated parallel imaging, enabling subsequent acquisition of both high spatial resolution CE-MR angiography and CE-MR venography after a single contrast injection without impairing the image quality. More extensive clinical studies are warranted to establish the range of applications and confirm the accuracy of this technique.

Objectives: We sought to implement and evaluate a high-performance, extended field of view protocol for time-resolved contrast-enhanced magnetic resonance imaging (CEMRA) of the carotid circulation by using a dedicated neurovascular (NV) array coil., Materials and Methods: A total of 16 adult volunteers and 20 clinical patients with suspected cerebrovascular disease (15 male, 21 female, 25-82 years of age) were scanned with a fast 3D MRA sequence (TR/TE: 2.16/1 milliseconds, sampling BW: 1090 Hz/pixel), with echo-sharing and parallel acquisition. All studies were performed on a 3.0 T MR system using an 8-channel neurovascular array coil. After injection of 6 mL of gadodiamide at 3 mL/s, a coronal 3D data set with in-plane resolution of 1 x 1.3 was implemented for 10 consecutive measurements each 1.8 seconds apart. The subjects subsequently underwent high spatial-resolution (in-plane: 0.8 x 0.9) CEMRA for comparative analysis. The quality of segmental arterial anatomy and the presence and degree of the arterial stenosis were evaluated by 2 neuroradiologists. The interobserver variability was tested by kappa statistics and comparative analysis between the TR-CEMRA and high spatial-resolution CEMRA was evaluated by mean of the Spearman rank correlation coefficient., Results: Craniocervical arteries were visualized with good image quality and definition in the diagnostic range. Occlusive disease was detected in 42 (reader A) and 44 (reader B) arterial segments with excellent interobserver agreement (kappa =0.89; 95% confidence interval 0.82-0.96). There was a significant correlation between the TR-CEMRA and high spatial-resolution CEMRA (Rs = 0.91 and 0.93, for readers A and B, respectively) for the degree of stenosis. Three aneurysms, 3 AVMs, 1 AV-fistula, and 2 subclavian steals were detected by both observers and were confirmed by correlative imaging., Conclusion: Time-resolved CEMRA at 3.0 T is reliable and versatile, providing 3-dimensional time-resolved data sets with high spatial (in plane: 1.3 x 1 mm2) and temporal (1.8 seconds) resolution over a large field of view. The higher signal-to-noise ratio gain at 3.0 T can be used effectively to improve performance of fast imaging and to support aggressive parallel acquisition protocols, as in the present study. Further clinical studies are required to establish the range of applications and the accuracy of the technique.