FLAIR Vascular Hyperintensities as a Surrogate of Collaterals in Acute Stroke: DWI Matters.

BACKGROUND AND PURPOSE: FLAIR vascular hyperintensities are thought to represent leptomeningeal collaterals in acute ischemic stroke. However, whether all-FLAIR vascular hyperintensities or FLAIR vascular hyperintensities-DWI mismatch, ie, FLAIR vascular hyperintensities beyond the DWI lesion, best reflects collaterals remains debated. We aimed to compare the value of FLAIR vascular hyperintensities-DWI mismatch versus all-FLAIR vascular hyperintensities for collateral assessment using PWI-derived collateral flow maps as a reference. MATERIALS AND METHODS: We retrospectively reviewed the registries of 6 large stroke centers and included all patients with acute stroke with anterior circulation large-vessel occlusion who underwent MR imaging with PWI before thrombectomy. Collateral status was graded from 1 to 4 on PWI-derived collateral flow maps and dichotomized into good (grades 3-4) and poor (grades 1-2). The extent of all-FLAIR vascular hyperintensities and FLAIR vascular hyperintensities-DWI mismatch was assessed on the 7 cortical ASPECTS regions, ranging from 0 (absence) to 7 (extensive), and associations with good collaterals were compared using receiver operating characteristic curves. RESULTS: Of the 209 included patients, 133 (64%) and 76 (36%) had good and poor collaterals, respectively. All-FLAIR vascular hyperintensity extent was similar between collateral groups (P = .76). Conversely, FLAIR vascular hyperintensities-DWI mismatch extent was significantly higher in patients with good compared with poor collaterals (P < .001). The area under the curve was 0.80 (95% CI, 0.74-0.87) for FLAIR vascular hyperintensities-DWI mismatch and 0.52 (95% CI, 0.44-0.60) for all-FLAIR vascular hyperintensities (P < .001 for the comparison), to predict good collaterals. Variables independently associated with good collaterals were smaller DWI lesion volume (P < .001) and larger FLAIR vascular hyperintensities-DWI mismatch (P = .02). CONCLUSIONS: In acute ischemic stroke with large-vessel occlusion, the extent of FLAIR vascular hyperintensities does not reliably reflect collateral status unless one accounts for DWI.

European Stroke Organisation (ESO) standard operating procedure for the preparation and publishing of guidelines.

The first European Stroke Organization (ESO) standard operating procedure (SOP) published in 2015 aimed at the implementation the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology to provide evidence-based guidelines for stroke management. This second ESO-SOP is aiming at further increase of the practicability of ESO guidelines and its technical implications. Authors comprised of the members of the ESO guideline Board and ESO Executive Committee. The final document was agreed on by several internal reviews. The second SOP comprises of the following aspects: rational for the SOP, the introduction of expert consensus statements, types of guideline documents, structures involved and detailed description of the guideline preparation process, handling of financial and intellectual conflicts of interest (CoI), involvement of ESO members in the guideline process, review process, authorship and publication policy, updating of guidelines, cooperation with other societies, and dealing with falsified data. This second SOP supersedes the first SOP published in 2015.

Benefit of first-pass complete reperfusion in thrombectomy is mediated by limited infarct growth.

BACKGROUND AND PURPOSE: The number of clot retrieval attempts required to achieve complete reperfusion by mechanical thrombectomy impacts functional outcome in acute ischaemic stroke (AIS). Complete reperfusion [expanded Treatment In Cerebral Infarction (eTICI) score = 3] at first pass (FP), is associated with the highest rates of favorable outcome compared to complete reperfusion by multiple passes. The aim of the present study was to investigate the relationship between FP complete reperfusion and infarct growth (IG). METHODS: Anterior AIS patients with baseline and 24-h diffusion-weighted magnetic resonance imaging were included from two prospective registries. IG was measured by voxel-based segmentation of initial and 24-h diffusion-weighted imaging lesions. IG and favorable 3-month modified Rankin Scale (mRS) score (≤ 2) were compared between patients in whom complete reperfusion (eTICI 3) was achieved with a single pass (FP group) and those for whom multiple passes were required (MP group), after matching for confounding factors. Mediation analysis was performed to examine the association between FP and 3-month mRS score, with IG as mediating variable. RESULTS: A total of 200 patients were included, of whom 118 (28.9%) had FP complete reperfusion. In case-control analysis, the FP group had lower IG than the MP group [8.7 (5.4-12.9) ml vs. 15.2 (11-22.6) ml, respectively; P = 0.03). Favorable outcome was higher in the FP population compared to a matched MP population (70.9% vs. 53.2%, respectively; P = 0.04). FP compete reperfusion (eTICI 3) was independently associated with favorable outcome in multivariable regression analysis [odds ratio 1.86, 95% confidence interval (CI) 1.01-4.39; P = 0.04]. The effect of complete reperfusion at FP on functional outcome was explained by limited IG in mediation analysis [indirect effect: -0.32 (95% CI -0.47 to -0.09)]. CONCLUSION: Complete reperfusion at FP is independently associated with significant decrease in IG compared to complete reperfusion by multiple attempts, explaining better functional outcomes.

Early neurological deterioration following thrombolysis for minor stroke with isolated internal carotid artery occlusion.

BACKGROUND AND PURPOSE: Better understanding the incidence, predictors and mechanisms of early neurological deterioration (END) following intravenous thrombolysis (IVT) for acute stroke with mild symptoms and isolated internal carotid artery occlusion (iICAo) may inform therapeutic decisions. METHODS: From a multicenter retrospective database, we extracted all patients with both National Institutes of Health Stroke Scale (NIHSS) score <6 and iICAo (i.e. not involving the Willis circle) on admission imaging, intended for IVT alone. END was defined as ≥4 NIHSS points increase within 24 h. END and no-END patients were compared for (i) pre-treatment clinical and imaging variables and (ii) occurrence of intracranial occlusion, carotid recanalization and parenchymal hemorrhage on follow-up imaging. RESULTS: Seventy-four patients were included, amongst whom 22 (30%) patients experienced END. Amongst pre-treatment variables, suprabulbar carotid occlusion was the only admission predictor of END following stepwise variable selection (odds ratio = 4.0, 95% confidence interval: 1.3-12.2; P = 0.015). On follow-up imaging, there was no instance of parenchymal hemorrhage, but an intracranial occlusion was now present in 76% vs. 0% of END and no-END patients, respectively (P < 0.001), and there was a trend toward higher carotid recanalization rate in END patients (29% vs. 9%, P = 0.07). As compared to no-END, END was strongly associated with a poor 3-month outcome. CONCLUSIONS: Early neurological deterioration is a frequent and highly deleterious event after IVT for minor stroke with iICAo, and is of thromboembolic origin in three out of four patients. The strong association with iICAo site-largely a function of underlying stroke etiology-may point to a different response of the thrombus to IVT. These findings suggest END may be preventable in this setting.

[Acquisition of clinical observation skills by medical students improves with discipline-based teaching. The example of neurological examination]. / L'enseignement par discipline de la sémiologie en deuxième année de médecine améliore l'acquisition des compétences. Exemple de la sémiologie neurologique.

INTRODUCTION: Since 2014-2015, practical teaching of clinical observation skills for 2nd year medical students at our faculty has been discipline-based; previously, each clinical lecturer had to cover all medical fields. We assessed the impact of this teaching reform on the neurological examination skills of medical students in a before-and-after study. METHODS: Pre-reform 3rd and post-reform 2nd and 3rd year medical students (n=62, n=71 and 52, respectively) had to perform 7 neurological examination items, for which performance criteria had been pre-defined. Subsequently, we assessed whether the mean grade in neurological examination skills during the test at the end of the 2nd year was different between students who had received neurological teaching from a neurologist (n=29) or another specialist (n=102). RESULTS: The median [interquartile range] number of items acquired by post-reform 3rd year students (4 [2-5]) was higher than that of pre-reform 3rd year students (2 [1-3]; P<0.001), but lower than that of post-reform 2nd year students (5 [4-6]; P=0.01). The mean grade obtained during the practical test was not different in students trained by a neurologist or another specialist. CONCLUSION: Acquisition of neurological examination skills improved after the teaching reform which consisted of: (1) a discipline-based practical teaching of clinical observation skills; (2) a training of clinical lecturers to teach a limited list of educational objectives; and (3) the introduction of a practical test at the end of the 2nd year of medical studies. However, there was a decline in clinical observation skills between 2nd and 3rd year medical students.

Do Fluid-Attenuated Inversion Recovery Vascular Hyperintensities Represent Good Collaterals before Reperfusion Therapy?

BACKGROUND AND PURPOSE: In acute ischemic stroke, whether FLAIR vascular hyperintensities represent good or poor collaterals remains controversial. We hypothesized that extensive FLAIR vascular hyperintensities correspond to good collaterals, as indirectly assessed by the hypoperfusion intensity ratio. MATERIALS AND METHODS: We included 244 consecutive patients eligible for reperfusion therapy with MCA stroke and pretreatment MR imaging with both FLAIR and PWI. The FLAIR vascular hyperintensity score was based on ASPECTS, ranging from 0 (no FLAIR vascular hyperintensity) to 7 (FLAIR vascular hyperintensities abutting all ASPECTS cortical areas). The hypoperfusion intensity ratio was defined as the ratio of the time-to-maximum >10-second over time-to-maximum >6-second lesion volumes. The median hypoperfusion intensity ratio was used to dichotomize good (low hypoperfusion intensity ratio) versus poor (high hypoperfusion intensity ratio) collaterals. We then studied the association between FLAIR vascular hyperintensity extent and hypoperfusion intensity ratio. RESULTS: Hypoperfusion was present in all patients, with a median hypoperfusion intensity ratio of 0.35 (interquartile range, 0.19-0.48). The median FLAIR vascular hyperintensity score was 4 (interquartile range, 3-5). The FLAIR vascular hyperintensities were more extensive in patients with good collaterals (hypoperfusion intensity ratio ≤0.35) than with poor collaterals (hypoperfusion intensity ratio >0.35; P for Trend = .016). The FLAIR vascular hyperintensity score was independently associated with good collaterals (P for Trend = .002). CONCLUSIONS: In patients eligible for reperfusion therapy, FLAIR vascular hyperintensity extent was associated with good collaterals, as assessed by the pretreatment hypoperfusion intensity ratio. The ASPECTS assessment of FLAIR vascular hyperintensities could be used to rapidly identify patients more likely to benefit from reperfusion therapy.

Can a 15-sec FLAIR replace conventional FLAIR sequence in stroke MR protocols?

BACKGROUND AND PURPOSE: Triage imaging facilitates the timely recognition of acute stroke with prognostic implications. Improvement in MR acquisition speed is needed given the extreme time constraints before treatment. We compared an ultrafast Echo-Planar FLAIR sequence (EPI-FLAIR) and a conventional FLAIR sequence (cFLAIR) for their diagnostic performances and ability to estimate the age of infarction. MATERIAL AND METHODS: Between June and August 2014, 125 consecutive patients (age 69±18 years, 48% men) admitted for a suspicion of acute (≤48-hrs) stroke were explored by both FLAIR sequences at 1.5-Tesla. EPI-FLAIR (15-sec) and cFLAIR (2-min and 15-sec) were compared by two readers, blinded to clinical data. RESULTS: EPI-FLAIR was less prone to kinetic artefacts than cFLAIR (2-3% vs. 23-49% depending on the reader, P<0.001). Diagnostic concordance was excellent for both readers (к>0.9). Amongst 8 hemorrhages, one subarachnoid hemorrhage presenting as a sudden deficit was missed on EPI-FLAIR sequence. Amongst 60 infarctions, cFLAIR and EPI-FLAIR were concordant in 50 (83%), while signal changes were visible on cFLAIR only in the remaining 10 (17%) cases. Amongst the 43 patients with known onset time (n=17 within 4.5hrs), FLAIR-DWI mismatch identified<4.5-hrs infarction with the same sensitivity (65%) using cFLAIR and EPI-FLAIR, but the positive predictive value (PPV) was higher for cFLAIR than for EPI-FLAIR (73% vs. 50%, P=0.008). CONCLUSION: EPI-FLAIR allows a drastic reduction of acquisition time devoted to FLAIR sequence and minimizes motion artifacts. Compared with cFLAIR, it is however associated with increased risk of undiagnosed stroke mimics and lower PPV for identifying<4.5-hrs infarctions.

Susceptibility vessel sign on T2* magnetic resonance imaging and recanalization results of mechanical thrombectomy with stent retrievers: a multicentre cohort study.

BACKGROUND AND PURPOSE: The susceptibility vessel sign (SVS) on T2*-weighted magnetic resonance imaging has been reported in several studies as a negative predictor of early recanalization after intravenous thrombolysis. The meaning of SVS regarding the results of mechanical thrombectomy with stent retrievers was investigated. METHODS: Susceptibility vessel sign presence and length were studied in 153 acute ischaemic stroke patients (82 men; mean ± SD age 59 ± 17 years, baseline National Institutes of Health Stroke Scale score 17.2 ± 6.5) from three stroke centres, treated with either mechanical thrombectomy alone (n = 84) or bridging therapy (n = 69). Variables were compared between recanalizers, defined as thrombolysis in cerebral infarction (TICI) scores ≥2b, and non-recanalizers (TICI<2b). RESULTS: The SVS was present in 113 (73.8%) patients. There was no association between the presence of SVS and recanalization, obtained in 86 (56.2%) patients, in the whole population [odds ratio (OR) 1.24, 95% confidence interval (CI) 0.53-2.92, P = 0.84) and in treatment subgroups (bridging: OR = 0.91, 95% CI 0.29-2.87, P = 1.0; thrombectomy alone: OR = 1.85, 95% CI 0.48-7.16, P = 0.54). However, in SVS+ patients, recanalization decreased with SVS length (OR 0.94 for each additional mm, 95% CI 0.89-0.99; P = 0.02). CONCLUSIONS: The success of recanalization in acute stroke patients treated with stent retrievers was related to thrombus length but not to the presence of SVS.

An update on brain imaging in transient ischemic attack.

Neuroimaging is critical in the evaluation of patients with transient ischemic attack (TIA) and MRI is the recommended modality to image an ischemic lesion. The presence of a diffusion (DWI) lesion in a patient with transient neurological symptoms confirms the vascular origin of the deficit and is predictive of a high risk of stroke. Refinement of MR studies including high resolution DWI and perfusion imaging using either MRI or CT further improve the detection of ischemic lesions. Rapid etiological work-up includes non-invasive imaging of cervical and intracranial arteries to search for symptomatic stenosis/occlusion associated with an increased risk of stroke.

Do FLAIR vascular hyperintensities beyond the DWI lesion represent the ischemic penumbra?

BACKGROUND AND PURPOSE: In acute stroke with proximal artery occlusion, FLAIR vascular hyperintensities observed beyond the boundaries of the cortical lesion on DWI (newly defined "FLAIR vascular hyperintensity-DWI mismatch") may be a marker of tissue at risk of infarction. Our aim was to compare the occurrence of FLAIR vascular hyperintensity-DWI mismatch relative to that of perfusion-weighted imaging-DWI mismatch in patients with proximal MCA occlusion before IV thrombolysis. MATERIALS AND METHODS: In 141 consecutive patients with proximal MCA occlusion, 2 independent observers analyzed FLAIR images for the presence of FLAIR vascular hyperintensity-DWI mismatch before IV thrombolysis. PWI-DWI mismatch was defined as Volumehypoperfusion > 1.8 × VolumeDWI, with Volumehypoperfusion > 6 seconds on time to maximum value of the residue function maps in the 94 patients with available PWI. The presence of FLAIR vascular hyperintensity-DWI mismatch, PWI-DWI mismatch, and infarct growth on 24-hour follow-up DWI was compared. RESULTS: A FLAIR vascular hyperintensity-DWI mismatch was present in 102/141 (72%) patients, with an excellent interobserver reliability (κ = 0.91), and a PWI-DWI mismatch, in 61 of the 94 (65%) patients with available PWI. FLAIR vascular hyperintensity-DWI mismatch predicted PWI-DWI mismatch with a sensitivity of 92% (95% CI, 85%-99%) and a specificity of 64% (95% CI, 47%-80%). Patients with FLAIR vascular hyperintensity-DWI mismatch had smaller initial DWI lesion and larger infarct growth (P < .001) than patients without FLAIR vascular hyperintensity-DWI mismatch, even though their final infarcts remained smaller (P < .001). CONCLUSIONS: Albeit being moderately specific, probably due to inclusion of oligemic tissue, the FLAIR vascular hyperintensity-DWI mismatch identifies large PWI-DWI mismatch with high sensitivity.

Intravenous thrombolysis for acute ischemic stroke.

Intravenous thrombolysis (IVT) with alteplase remains the standard treatment for acute ischemic stroke. Although IVT can be started up to 4.5 hours after symptoms' onset, it is all the more effective and safe when started early. It allows a 10% absolute reduction in the risk of handicap or death at 3 months, despite a 2-7% risk of symptomatic intracranial hemorrhage. Current research efforts involve firstly trying to treat a larger proportion of patients by overcoming some of the contraindications to IVT and secondly assessing combined or alternative treatments to achieve a higher early recanalization rate.

MR screening of candidates for thrombolysis: How to identify stroke mimics?

Stroke mimics account for up to a third of suspected strokes. The main causes are epileptic deficit, migraine aura, hypoglycemia, and functional disorders. Accurate recognition of stroke mimics is important for adequate identification of candidates for thrombolysis. This decreases the number of unnecessary treatments and invasive vascular investigations. Correctly identifying the cause of symptoms also avoids delaying proper care. Therefore, this pictorial review focuses on what the radiologist should know about the most common MRI patterns of stroke mimics in the first hours after onset of symptoms. The issues linked to the accurate diagnosis of stroke mimics in the management of candidates for thrombolysis will be discussed.